LEIS user's publications

This page contains a list of publications on Low Energy Ion Scattering (LEIS), compiled by the participants of the LEIS user's meeting.

The list consists of summarized information at the top (authors, title, keywords, year). Extended information can be found at the bottom, by clicking on the hyperlink. The list is sorted by year, with the most recent publications at the top.

To submit your LEIS related publications for this list, please email Rik ter Veen (rik dot ter dot veen at tascon-gmbh dot de) with an Excel file with authors, title, journal, volume, issue, pages, year, DOI, keywords, and abstract.

D. Farka, H. Coskun, P. Bauer, D. Roth, B. Bruckner, Petr Klapetek, N. S. Sariciftci, and P. Stadler (2017)

Increase in electron scattering length in PEDOT:PSS by a triflic acid post-processing

Transparent conductive electrodes Conductive metallic polymers Anderson localization Mott–Ioffe–Regel limit Infrared transparency

Abstract

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D. Roth, B. Bruckner, M. V. Moro, S. Gruber, D. Goebl, J. I. Juaristi, M. Alducin, R. Steinberger, J. Duchoslav, D. Primetzhofer, and P. Bauer (2017)

Electronic Stopping of Slow Protons in Transition and Rare Earth Metals: Breakdown of the Free Electron Gas Concept

TOTAL-ENERGY CALCULATIONS; AUGMENTED-WAVE METHOD; LIGHT-IONS; BASIS-SET; POWERS; IRRADIATION; GADOLINIUM; VELOCITY; SPECTRA; SOLIDS

Abstract

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R. Coloma Ribera, R.W.E. v.d. Kruijs, J.M. Sturm, A.E. Yakshin and F. Bijkerk (2017)

Intermixing and thermal oxidation of ZrO2 thin films grown on a-Si, SiN, and SiO2 by metallic and oxidic mode magnetron sputtering

Abstract

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R. Steinberger, C.E. Celedón, B. Bruckner, D. Roth, J. Duchoslav, M. Arndt, P. Kürnsteiner, T. Steck, J. Faderl, C.K. Riener, G. Angeli, P. Bauer, D. Stifter (2017)

Oxygen accumulation on metal surfaces investigated by XPS, AES and LEIS, an is-sue for sputter depth profiling under UHV conditions

XPS, AES, LEIS, Oxygen, accumulation, residual gas

Abstract

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Almeida, Rui M.; Jain, Himanshu; Pantano, Carlo G.; Mauro, J. (2016)

Low-Energy Ion-Scattering Spectroscopy of Modified Silicate Glasses.

Glass; Depth Profiling; LEIS; Qtac; Application Paper

Abstract

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Cushman, Cody V.; Brüner, Philipp; Zakel, Julia; Major, George H.; Lunt, Barry M.; Smith, Nicholas J. et al. (2016)

Low energy ion scattering (LEIS). A practical introduction to its theory, instrumentation, and applications.

LEIS; Qtac

Abstract

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Hägglund, Carl; Grehl, Thomas; Tanskanen, Jukka T.; Yee, Ye Sheng; Mullings, Marja N.; Mackus, Adriaan J. M. et al. (2016)

Growth, intermixing, and surface phase formation for zinc tin oxide nanolaminates produced by atomic layer deposition.

ALD; Display Technology; Thin films; LEIS; Qtac; Multiple Techniques; Application Paper

Abstract

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He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; Liu, Qingcai; Tumuluri, Uma; Wu, Zili; Wachs, Israel E. (2016)

Influence of catalyst synthesis method on selective catalytic reduction (SCR) of NO by NH3 with V2O5-WO3/TiO2 catalysts.

Catalysis; Catalysts; LEIS; Qtac; Multiple Techniques; Application Paper

Abstract

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Keturakis, Christopher J.; Notis, Ben; Blenheim, Alex; Miller, Alfred C.; Pafchek, Rob; Notis, Michael R.; Wachs, Israel E. (2016)

Analysis of corrosion layers in ancient Roman silver coins with high resolution surface spectroscopic techniques.

LEIS; Qtac; XPS; Application Paper

Abstract

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Longo, Roberto C.; Mattson, Eric C.; Vega, Abraham; Cabrera, Wilfredo; Cho, Kyeongjae; Chabal, Yves J.; Thissen, Peter (2016)

Mechanism of Arsenic Monolayer Doping of Oxide-Free Si(111).

Semiconductors; Implants; LEIS; Qtac; XPS; Application Paper

Abstract

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R. Coloma Ribera, R. W. E. van de Kruijs, J. M. Sturm, A. E. Yakshin, and F. Bijkerk (2016)

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

surface structure, surface segregation, ion-surface impact, silicon compounds, sputter deposition, ruthenium, metallic thin films, X-ray photoelectron spectra, silicon

Abstract

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Simon R. Bare, Axel Knop-Gericke, Detre Teschner, Michael Hävacker, Raoul Blume, Tulio Rocha, Robert Schlögl, Ally S.Y. Chan, N. Blackwell, M.E. Charochak, Rik ter Veen, Hidde H. Brongersma (2016)

Surface Analysis of Zeolites: An XPS, Variable Kinetic Energy XPS, and Low Energy Ion Scattering Study

Zeolite; XPS; X-ray photoelectron spectroscopy; low energy ion scattering spectroscopy; LEIS; catalysis

Abstract

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ter Veen, Rik (2016)

Statistical Quantification of LEIS Data

Abstract

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Brüner, Philipp; Grehl, Thomas; Brongersma, Hidde; Detlefs, Blanka; Nolot, Emmanuel; Grampeix, Helen et al (2015)

Thin film analysis by low-energy ion scattering by use of TRBS simulations.

ALD; Semiconductors; Thin films; Data Analysis; Quantification; LEIS; Qtac; Fundamental Paper

Abstract

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D. Goebl, B. Bruckner, D. Roth, C. Ahamer and P. Bauer (2015)

Low-energy ion scattering: a quantitative method?

LEIS; Surface composition analysis; Information depth; Matrix effects

Abstract

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Giraudo, Nicolas; Krolla-Sidenstein, Peter; Bergdolt, Samuel; Heinle, Marita; Gliemann, Hartmut; Messerschmidt, Florian et al. (2015)

Early Stage Hydration of Wollastonite: Kinetic Aspects of the Metal-Proton Exchange Reaction.

Qtac; MEIS; Application Paper

Abstract

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Illiberi, A.; Cobb, B.; Sharma, A.; Grehl, T.; Brongersma, H.; Roozeboom, F. et al. (2015)

Spatial Atmospheric Atomic Layer Deposition of InxGayZnzO for Thin Film Transistors.

ALD; Complex Oxides; Display Technology; Thin films; LEIS; Qtac; Application Paper

Abstract

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Longo, Roberto C.; Cho, Kyeongjae; Brüner, Philipp; Welle, Alexander; Gerdes, Andreas; Thissen, Peter (2015)

Carbonation of wollastonite(001) competing hydration: microscopic insights from ion spectroscopy and density functional theory.

LEIS; Qtac; Application Paper

Abstract

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M. Dosmailov, L.N. Leonat, J. Patek, D. Roth, P. Bauer, M.C. Scharber, N.S. Sariciftci, J.D. Pedarnig (2015)

Transparent conductive ZnO layers on polymer substrates: thin film deposition and application in organic solar cells

Transparent conductive zinc oxide; Polymer substrate; Polyethylene terephthalate; Pulsed-laser deposition; Rutherford back scattering analysis; Organic solar cells

Abstract

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P.J. van Zwol, D.F. Vles, W.P. Voorthuijzen, M. Péter, H. Vermeulen, W.J. van der Zande, J.M. Sturm, R.W.E. van de Kruijs and F. Bijkerk (2015)

Emissivity of freestanding membranes with thin metal coatings,

Extreme UV lithography, pellicles, emissivity, metal coatings

Abstract

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Rupp, Ghislain M.; Téllez, Helena; Druce, John; Limbeck, Andreas; Ishihara, Tatsumi; Kilner, John; Fleig, Jürgen (2015)

Surface chemistry of La 0.6 Sr 0.4 CoO 3−δ thin films and its impact on the oxygen surface exchange resistance.

Ceramics; Fuel Cells; LEIS; Qtac; Application Paper

Abstract

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S. Prusa, P. Prochazka, P. Babor, T. Sikola, R. ter Veen, M. Fartmann, T. Grehl, Ph. Brüner, D. Roth, P. Bauer, H.H. Brongersma (2015)

Highly Sensitive Detection of Surface and Intercalated Impurities in Graphene by LEIS

Carbon Graphene LEIS

Abstract

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Symianakis, Emmanouil; Malko, Daniel; Ahmad, Ehsan; Mamede, Anne-Sophie; Paul, Jean-Francois; Harrison, Nicholas; Kucernak, Anthony (2015)

Electrochemical Characterization and Quantified Surface Termination Obtained by Low Energy Ion Scattering and X-ray Photoelectron Spectroscopy of Orthorhombic and Rhombohedral LaMnO3 Powders.

Catalysis; Catalysts; Ceramics; Fuel Cells; LEIS; Qtac; XPS; Application Paper

Abstract

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T.M.C. Hoang, B. Geerdink, J.M. Sturm, L. Lefferts and K. Seshan (2015)

Steam reforming of acetic acid - A major component in the volatiles formed during gasification of humin

Steam reforming, Acetic acid, Humin, Nickel, Ceria–zirconia

Abstract

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Villar-Garcia, Ignacio J.; Fearn, Sarah; Ismail, Nur L.; McIntosh, Alastair J S; Lovelock, Kevin R J (2015)

Fine tuning the ionic liquid-vacuum outer atomic surface using ion mixtures.

Ionic Liquids; LEIS; Qtac; Application Paper

Abstract

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Chen, Guangxu; Zhao, Yun; Fu, Gang; Duchesne, Paul N.; Gu, Lin; Zheng, Yanping et al. (2014)

Interfacial effects in iron-nickel hydroxide-platinum nanoparticles enhance catalytic oxidation. INCLUDING SUPPLEMENTAL MATERIAL.

Catalysis; Catalysts; Nanoparticles; LEIS; Qtac; Multiple Techniques; Application Paper

Abstract

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D. Goebl, W. Roessler, D. Roth, and P. Bauer (2014)

Influence of the excitation threshold of d electrons on electronic stopping of slow light ions

ENERGY NE+ SCATTERING; D-BAND METALS; CROSS-SECTIONS; CHARGE-EXCHANGE; PHOTOEMISSION SPECTRA; SURFACE SCATTERING; GAS; POWER; VELOCITY; AL

Abstract

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D. Primetzhofer, M. Sytnyk, P. J. Wagner, P. Bauer, W. Heiss (2014)

The potential of Rutherford Backscattering Spectrometry for composition analysis of colloidal nanocrystals

RBS; Elastic scattering; Nanocrystal; Cation-exchange

Abstract

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Druce, John; Ishihara, Tatsumi; Kilner, John (2014)

Surface composition of perovskite-type materials studied by Low Energy Ion Scattering (LEIS).

Ceramics; Complex Oxides; Fuel Cells; LEIS; Qtac; Application Paper

Abstract

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Druce, John; Simrick, Neil; Ishihara, Tatsumi; Kilner, John (2014)

“Imaging” LEIS of micro-patterned solid oxide fuel cell electrodes.

Ceramics; Complex Oxides; Fuel Cells; Imaging; LEIS; Qtac; Application Paper

Abstract

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Druce, John; Téllez, Helena; Simrick, Neil; Ishihara, Tatsumi; Kilner, John (2014)

Surface composition of solid oxide electrode structures by laterally resolved low energy ion scattering (LEIS).

Fuel Cells; Imaging; LEIS; Qtac; Application Paper

Abstract

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Erkens, Ivo J. M.; Verheijen, Marcel A.; Knoops, Harm C. M.; Landaluce, Tatiana F.; Roozeboom, Fred; Kessels, Wilhelmus M. M. (2014)

Plasma-Assisted Atomic Layer Deposition of PtO x from (MeCp)PtMe 3 and O 2 Plasma.

ALD; Thin Film Deposition; Thin films; LEIS; Qtac; Application Paper

Abstract

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Ignacio J. Villar-Garcia, Sarah Fearn, Gilbert F. De Gregorio, Nur L. Ismail, Florence J. V. Gschwend, Alastair J. S. McIntosh and Kevin R. J. Lovelock

 (2014)

The ionic liquid - vacuum outer atomic surface: a low-energy ion scattering study

LEIS ionic liquids

Abstract

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Téllez, Helena; Aguadero, Ainara; Druce, John; Burriel, Mónica; Fearn, Sarah; Ishihara, Tatsumi et al. (2014)

New perspectives in the surface analysis of energy materials by combined time-of-flight secondary ion mass spectrometry (ToF-SIMS) and high sensitivity low-energy ion scattering (HS-LEIS).

Ceramics; Fuel Cells; LEIS; Qtac; TOF-SIMS; Application Paper

Abstract

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Téllez, Helena; Druce, John; Hall, Allen; Ishihara, Tatsumi; Kilner, John; Rockett, Angus (2014)

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se 2 for photovoltaic applications.

Photovoltaics; LEIS; Qtac; Application Paper

Abstract

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Téllez, Helena; Druce, John; Ju, Young-Wan; Kilner, John; Ishihara, Tatsumi (2014)

Surface chemistry evolution in LnBaCo2O5 + δ double perovskites for oxygen electrodes.

Ceramics; Complex Oxides; Fuel Cells; LEIS; Qtac;  Multiple Techniques; Application Paper

Abstract

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Villar-Garcia, Ignacio J.; Fearn, Sarah; De Gregorio, Gilbert F.; Ismail, Nur L.; Gschwend, Florence J. V.; McIntosh, Alastair J. S.; Lovelock, Kevin R. J. (2014)

The ionic liquid–vacuum outer atomic surface: a low-energy ion scattering study.

Ionic Liquids; LEIS; Qtac; Application Paper

Abstract

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M.Sytnyk, R. Kirchschlager, M.I. Bodnarchuk, D. Primetzhofer, D. Kriegner, H. Enser, J. Stangl, P. Bauer, M. Voith, A.W. Hassel, F. Krumeich, F. Ludwig, A. Meingast, G. Kothleitner, M.V. Kovalenko, W. Heiss, (2013)

Tuning the Magnetic Properties of Metal Oxide Nanocrystal Heterostructures by Cation Exchange

magnetic nanocrystals, cation exchange, exchange bias, nanoheterostructures, ferrites

Abstract

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Brongersma, Hidde H.; Brüner, Philipp; Grehl, Thomas; ter Veen, Henrik R. J.; Bauer, Peter; van den Berg, Jaap A. et al. (2013)

High Resolution In-Depth Analysis with Low-Energy Ion Scattering: Experiments and Simulation.

LEIS; Qtac; Review Paper

Abstract

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Burriel, Mónica; Wilkins, Stuart; Hill, John P.; Muñoz-Márquez, Miguel A.; Brongersma, Hidde H.; Kilner, John A. et al. (2013)

Absence of Ni on the outer surface of Sr doped La2NiO4 single crystals.

Complex Oxides; Single Crystals; LEIS; Qtac; XPS; Application Paper

Abstract

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D. Goebl, D. Primetzhofer, E. Abad, R. C. Monreal and P. Bauer (2013)

Auger neutralization of He+ on Cu surfaces: simulation of azimuthal scans

LEIS, Charge exchange, Auger-neutralization, Ion fraction, Cun surfaces

Abstract

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D. Goebl, D. Roth, D. Primetzhofer, A. Putz and P. Bauer (2013)

Quasi-resonant neutralization of He+ ions at a Germanium surface

Abstract

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Kauling, Alan; Ebeling, Günter; Morais, Jonder; Pádua, Agílio; Grehl, Thomas; Brongersma, Hidde H.; Dupont, Jairton (2013)

Surface composition/organization of ionic liquids with Au nanoparticles revealed by high-sensitivity low-energy ion scattering.

Ionic Liquids; Nanoparticles; LEIS; Qtac; Application Paper

Abstract

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Kersting, R.; Breitenstein, D.; Hagenhoff, B.; Fartmann, M.; Heller, D.; Grehl, T. et al. (2013)

Surface characterization of nanoparticles: different surface analytical techniques compared. SIMS XVIII Proceedings.

Application paper LEIS TOF-SIMS Multiple techniquesThin film deposition (PVD, CVD)

Abstract

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Phivilay, Somphonh P.; Puretzky, Alexander A.; Domen, Kazunari; Wachs, Israel E. (2013)

Nature of Catalytic Active Sites Present on the Surface of Advanced Bulk Tantalum Mixed Oxide Photocatalysts.

Catalysis; Catalysts; LEIS; Qtac; Multiple Techniques; Application Paper

Abstract

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Phivilay, Somphonh P.; Roberts, Charles A.; Puretzky, Alexander A.; Domen, Kazunari; Wachs, Israel E. (2013)

Fundamental Bulk/Surface Structure–Photoactivity Relationships of Supported (Rh 2– y Cr y O 3 )/GaN Photocatalysts.

Catalysis; Catalysts; LEIS; Qtac; Multiple Techniques; Application Paper

Abstract

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R.C. Monreal, D. Goebl, D. Primetzhofer, and P. Bauer (2013)

Effects of the atomic level shift in the Auger neutralization rates of noble metal surfaces

Charge exchange, Auger neutralization, LEIS, Noble metals

Abstract

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Rafati, Ali; ter Veen, Rik; Castner, David G. (2013)

Low energy ion scattering: Determining overlayer thickness for functionalized gold nanoparticles.

Nanoparticles; LEIS; Qtac

Abstract

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Rik ter Veen, Michael Fartmann, Reinhard Kersting, and Birgit Hagenhoff (2013)

Combining dynamic and static depth profiling in low energy ion scattering

LEIS; Qtac

Abstract

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Shin, Hyun Ho; McIntosh, Steven (2013)

On the H2/D2 isotopic exchange rate of proton conducting barium cerates and zirconates.

Ceramics; Fuel Cells; LEIS; Qtac

Abstract

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Wachs, Israel E.; Phivilay, Somphonh P.; Roberts, Charles A. (2013)

Reporting of Reactivity for Heterogeneous Photocatalysis.

LEIS; Qtac; Application Paper

Abstract

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Bruns, M.; Barth, C.; Brüner, P.; Engin, S.; Grehl, T.; Howell, C. et al. (2012)

Structure and chemical composition of mixed benzylguanine- and methoxy-terminated self-assembled monolayers for immobilization of biomolecules. ECASIA special issue paper.

Self Assembled Monolayers; LEIS; Qtac; XPS; Application Paper

Abstract

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Téllez, H.; Chater, R. J.; Fearn, S.; Symianakis, E.; Brongersma, H. H.; Kilner, J. A. (2012)

Determination of 16O and 18O sensitivity factors and charge-exchange processes in low-energy ion scattering.

Fuel Cells; LEIS; Qtac; Application Paper; Instrumental Paper

Abstract

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Brumbach, Michael T.; Ohlhausen, James A.; Zavadil, Kevin R.; Snow, Clark S.; Woicik, Joseph C. (2011)

Activation of erbium films for hydrogen storage.

LEIS; Qtac; Application Paper

Abstract

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Grehl, T.; Niehuis, E.; Brongersma, H. H. (2011)

Surface Microanalysis by Low-Energy Ion Scattering.

LEIS; Qtac; Commercial Paper; Review Paper

Abstract

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Kilner, John A.; Skinner, Stephen J.; Brongersma, Hidde H. (2011)

The isotope exchange depth profiling (IEDP) technique using SIMS and LEIS.

Fuel Cells; LEIS; Qtac; TOF-SIMS; Application Paper; Review Paper

Abstract

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Py, Matthieu; Barnes, Jean Paul; Grehl, Thomas; Brüner, Philipp; Gambacorti, Narciso; Hartmann, J. M. (2011)

Quantitative profiling of SiGe/Si superlattices with extended Full Spectrum ToF-SIMS and LEIS. Poster.

Semiconductors; SiGe; LEIS; Qtac; TOF-SIMS; Application Paper

Abstract

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Beekmans, H.; Breitenstein, Daniel; Brongersma, Hidde H.; de Ridder, Marco; Tromp, Th.J. (2010)

Significant improvement of the osseointegration of zirconia dental implants by HS-LEIS analysis.

LEIS; Qtac; Application Paper

Abstract

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Brongersma, Hidde H.; Grehl, Thomas; Schofield, Emma R.; Smith, Richard A.P.; ter Veen, Hendrik R.J. (2010)

Analysis of the Outer Surface of Platinum-Gold Catalysts by Low-Energy Ion Scattering.

LEIS; Catalysis; Catalysts; Qtac; Instrumental Paper

Abstract

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Brongersma, Hidde H.; Grehl, Thomas; van Hal, Paul A.; Kuijpers, Niels C.W.; Mathijssen, Simon G.J.; Schofield, Emma R. et al. (2010)

High-sensitivity and high-resolution low-energy ion scattering.

LEIS; Qtac; Review Paper

Abstract

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Fuchs, M.; Breitenstein, Daniel; Fartmann, Michael; Grehl, Thomas; Koester, R.; Ochs, R. et al. (2010)

Characterization of core/shell nanoparticle thin films for gas analytical applications.

Nanoparticles; LEIS; Qtac; Application Paper

Abstract

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H. Beekmans, D. Breitenstein, H.H. Brongersma, M. de Ridder, Th.J. Tromp (2010)

Significant improvement of the osseointegration of zirconia dental implants by HS-LEIS analysis

LEIS; Zirconia; Dental implant; Surface composition; Surface analysis; Cleaning

Abstract

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H. H. Brongersma, T. Grehl, E. R. Schofield, R. A. P. Smith and H. R. J. ter Veen, (2010)

Analysis of the Outer Surface of Platinum-Gold Catalysts by Low-Energy Ion Scattering. Improved resolution allows selective analysis of mixed metal systems

Abstract

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H. H. Brongersma, T. Grehl, P. A. van Hal, N. C. W. Kuijpers, S. G. J. Mathijssen, E. R. Schofield, R. A. P. Smith and H. R. J. ter Veen, (2010)

High-sensitivity and high-resolution low-energy ion scattering

LEIS, High sensitivity, Mass resolution, Depth resolution, Self-assembled monolayer

Abstract

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V. I. T. A. d. Rooij-Lohmann, A. E. Yakshin, R. W. E. v. d. Kruijs, E. Zoethout, A. W. Kleyn, E. G. Keim, M. Gorgoi, F. Schäfers, H. H. Brongersma and F. Bijkerk, (2010)

Enhanced diffusion upon amorphous-to-nanocrystalline phase transition in Mo/B4C/Si layered systems

Abstract

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H. R. J. ter Veen, T. Kim, I. E. Wachs and H. H. Brongersma, (2009)

Applications of High Sensitivity-Low Energy Ion Scattering (HS-LEIS) in heterogeneous catalysis

High Sensitivity-Low Energy Ion Scattering (HS-LEIS), Heterogeneous catalysis, Surface analysis, MoO3/TiO2

Abstract

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R. Andrzejewski, V. Kuzmin, D. O. Boerma, D. Primetzhofer, S. N. Markin and P. Bauer, (2009)

Azimuthal scans in LEIS: Influence of the scattering potential

Abstract

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T. Tanabe, Y. Nagai, T. Hirabayashi, N. Takagi, K. Dohmae, N. Takahashi, S. i. Matsumoto, H. Shinjoh, J. N. Kondo, J. C. Schouten and H. H. Brongersma, (2009)

Low temperature CO pulse adsorption for the determination of Pt particle size in a Pt/cerium-based oxide catalyst

Pt particle size, Cerium-based oxide, CO adsorption, X-ray diffraction, Low energy ion scattering

Abstract

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T. Wu, W. E. Kaden, W. A. Kunkel and S. L. Anderson, (2009)

Size-dependent oxidation of Pdn (n [less-than-or-equals, slant] 13) on alumina/NiAl(110): Correlation with Pd core level binding energies

Low energy ion scattering (LEIS), X-ray photoelectron spectroscopy, Oxidation, Palladium, Alumina

Abstract

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V. I. T. A. d. Rooij-Lohmann, A. W. Kleyn, F. Bijkerk, H. H. Brongersma and A. E. Yakshin, (2009)

Diffusion and interaction studied nondestructively and in real-time with depth-resolved low energy ion spectroscopy

Atomic, molecular and ion beam impact and interactions with surfaces. Self-diffusion and ionic conduction in solid nonmetals

Abstract

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Y. Yun, N. Pilet, U. D. Schwarz and E. I. Altman, (2009)

Comparison of the interaction of Pd with positively and negatively poled LiNbO3(0 0 0 1)

Palladium, Metal-insulator interfaces, Carbon monoxide, Thermal desorption, X-ray photoelectron spectroscopy, Low energy ion scattering (LEIS)

Abstract

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A. Celaya Sanfiz, T. W. Hansen, A. Sakthivel, A. Trunschke, R. Schlögl, A. Knoester, H. H. Brongersma, M. H. Looi and S. B. A. Hamid, (2008)

How important is the (001) plane of M1 for selective oxidation of propane to acrylic acid?

MoVTeNb oxide catalyst, M1, Propane oxidation, Propane ammoxidation, Low-energy ion scattering, LEIS

Abstract

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D. Primetzhofer, S. Markin, J. Juaristi, E. Taglauer and P. Bauer, (2008)

Crystal Effects in the Neutralization of He+ Ions in the Low Energy Ion Scattering Regime

Abstract

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D. Primetzhofer, S. N. Markin, M. Draxler, R. Beikler, E. Taglauer and P. Bauer, (2008)

Strength of the interatomic potential derived from angular scans in LEIS

Abstract

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D. Primetzhofer, S. N. Markin, P. Zeppenfeld, P. Bauer, S. Prusa, M. Kolibal and T. Sikola, (2008)

Quantitative analysis of ultra thin layer growth by time-of-flight low energy ion scattering

Abstract

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K. Khalal-Kouache, B. Aissous, A. Mekhtiche and A. C. Chami, (2008)

Effect of energy loss in the simulation of slow ion scattering by a solid surface

Simulation, Energy loss, Multiple scattering, Monte Carlo, Transport theory, [pacs] 68.49.Sf, [pacs] 34.50.Bw, [pacs] 07.05.Tp, Ion surface scattering

Abstract

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D. Primetzhofer, S. N. Markin, R. Kolarova, M. Draxler, R. Beikler, E. Taglauer and P. Bauer, (2007)

On the surface sensitivity of angular scans in LEIS

Abstract

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H. H. Brongersma, M. Draxler, M. de Ridder and P. Bauer, (2007)

Surface composition analysis by low-energy ion scattering

LEIS, ISS, Quantitative surface composition analysis

Abstract

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S. P. Chenakin, R. Kolarova, S. N. Markin, D. Primetzhofer and P. Bauer, (2007)

Influence of screening and electronic stopping on LEIS spectra

Abstract

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E. van der Wal, S. J. Oldenburg, T. Heij, A. W. Denier van der Gon, H. H. Brongersma, J. G. C. Wolke, J. A. Jansen and A. M. Vredenberg, (2006)

Adsorption and desorption of Ca and PO"4 species from SBFs on RF-sputtered calcium phosphate thin films

Abstract

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V. V. Guliants, R. Bhandari, A. R. Hughett, S. Bhatt, B. D. Schuler, H. H. Brongersma, A. Knoester, A. M. Gaffney and S. Han, (2006)

Probe molecule chemisorption-low energy ion scattering study of surface active sites present in the orthorhombic Mo-V-(Te-Nb)-O catalysts for propane (amm)oxidation.

Abstract

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A. Delabie, R. L. Puurunen, B. Brijs, M. Caymax, T. Conard, B. Onsia, O. Richard, W. Vandervorst, C. Zhao, M. M. Heyns, M. Meuris, M. M. Viitanen, H. H. Brongersma, M. d. Ridder, L. V. Goncharova, E. Garfunkel, T. Gustafsson and W. Tsai, (2005)

Atomic layer deposition of hafnium oxide on germanium substrates

Abstract

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F. J. J. Janssen, A. W. Denier van der Gon, L. J. van IJzendoorn, R. Thoelen, M. J. A. de Voigt and H. H. Brongersma, (2005)

The influence of surface treatments on cathode formation and stability in polymer light emitting diodes

Conjugated polymers, Light emitting diodes, Surface treatment, Stability, Low energy ion scattering

Abstract

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J. Zhu, J. G. van Ommen, A. Knoester and L. Lefferts, (2005)

Effect of surface composition of yttrium-stabilized zirconia on partial oxidation of methane to synthesis gas

Abstract

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M. Draxler, J. E. Valdes, R. Beikler and P. Bauer, (2005)

On the extraction of neutralisation information from low energy ion scattering spectra

Abstract

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M. Draxler, P. Zeppenfeld, R. Beikler, E. Taglauer and P. Bauer, (2005)

Ion and neutral scattering spectra in LEIS

Abstract

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V. V. Guliants, R. Bhandari, B. Swaminathan, V. K. Vasudevan, H. H. Brongersma, A. Knoester, A. M. Gaffney and S. Han, (2005)

Roles of surface Te, Nb, and Sb oxides in propane oxidation to acrylic acid over bulk orthorhombic Mo-V-O phase.

Abstract

________________________________

V. V. Guliants, R. Bhandari, H. H. Brongersma, A. Knoester, A. M. Gaffney and S. Han, (2005)

A study of the surface region of the Mo-V-Te-O catalysts for propane oxidation to acrylic acid.

Abstract

________________________________

R. D. v. d. Grampel, W. Ming, A. Gildenpfennig, J. Laven, H. H. Brongersma, G. d. With and R. v. d. Linde, (2004)

Quantification of Fluorine Density in the Outermost Atomic Layer

Abstract

________________________________

R. D. van de Grampel, W. Ming, A. Gildenpfennig, W. J. H. van Gennip, J. Laven, J. W. Niemantsverdriet, H. H. Brongersma, G. de With and R. van der Linde, (2004)

The outermost atomic layer of thin films of fluorinated polymethacrylates.

Abstract

________________________________

R. L. Puurunen and W. Vandervorst, (2004)

Island growth as a growth mode in atomic layer deposition: A phenomenological model

Abstract

________________________________

R. L. Puurunen, W. Vandervorst, W. F. A. Besling, O. Richard, H. Bender, T. Conard, C. Zhao, A. Delabie, M. Caymax, S. D. Gendt, M. Heyns, M. M. Viitanen, M. d. Ridder, H. H. Brongersma, Y. Tamminga, T. Dao, T. d. Win, M. Verheijen, M. Kaiser and M. Tuomi (2004)

Island growth in the atomic layer deposition of zirconium oxide and aluminum oxide on hydrogen-terminated silicon: Growth mode ...

Abstract

________________________________

S. Y. Grachev, J. M. Gallego, D. Ecija, D. O. Boerma, R. Gonzalez-Arrabal and R. Miranda, (2004)

A combined LEIS/STM study of two types of surface reconstruction of magnetic Fe"4N layers

Abstract

________________________________

W. P. A. Jansen, A. Knoester, A. J. H. Maas, P. Schmit, A. Kytökivi, A. W. Denier v.d. Gon and H. H. Brongersma, (2004)

Influence of compaction and surface roughness on low-energy ion scattering signals

surface roughness; neutralization; LEIS; ISS; compaction

Abstract

________________________________

B. Moest, S. Helfensteyn, P. Deurinck, M. Nelis, A. W. Denier van der Gon, H. H. Brongersma, C. Creemers and B. E. Nieuwenhuys, (2003)

The surface and step edge composition of clean and oxygen covered Pt50Rh50(5 1 1)

Alloys, Vicinal single crystal surfaces, Surface segregation, Platinum, Rhodium, Ion scattering spectroscopy, Low energy ion scattering (LEIS), Ion-solid interactions

Abstract

________________________________

H. H. Brongersma, M. de Ridder, A. Gildenpfennig and M. M. Viitanen, (2003)

Insight in the outside: materials science at the atomic level using LEIS

Films, Fuel Cells, Perovskites, Self-assembly, Surfaces

Abstract

________________________________

M. de Ridder, A. G. J. Vervoort, R. G. van Welzenis and H. H. Brongersma, (2003)

The limiting factor for oxygen exchange at the surface of fuel cell electrolytes

Surface composition, Impurities, Oxygen exchange, Yttria stabilised zirconia (YSZ), Low energy ion scattering (LEIS)

Abstract

________________________________

M. de Ridder, R. G. van Welzenis, H. H. Brongersma and U. Kreissig, (2003)

Oxygen exchange and diffusion in the near surface of pure and modified yttria-stabilised zirconia

Abstract

________________________________

M. Draxler, R. Beikler, E. Taglauer, K. Schmid, R. Gruber, S. N. Ermolov and P. Bauer, (2003)

Explanation of the surface peak in charge integrated LEIS spectra

Abstract

________________________________

A. G. J. Vervoort, P. J. Scanlon, M. de Ridder, H. H. Brongersma and R. G. van Welzenis, (2002)

Surface modification of a fuel cell material by ion implantation

Yttria stabilized zirconia, Low-energy ion scattering, Solid oxide fuel cell, Implantation, Segregation

Abstract

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F. J. J. Janssen, L. J. van IJzendoorn, H. F. M. Schoo, J. M. Sturm, G. G. Andersson, A. W. D. van der Gon, H. H. Brongersma and M. J. A. de Voigt, (2002)

Degradation effects in poly para-phenylene vinylene derivatives due to controlled oxygen exposure

Conducting polymers, Light emitting diodes, Oxygen, Elastic recoil detection analysis, Polymer structure, Electrical characterisation

Abstract

________________________________

G. G. Andersson, W. J. H. van Gennip, J. W. Niemantsverdriet and H. H. Brongersma, (2002)

Calcium induced oxidation of PPV studied with X-ray photoelectron spectroscopy and secondary ion mass spectrometry

Polymer light emitting diodes, Degradation mechanism, Polymer-metal interfaces, X-ray photoelectron spectroscopy (XPS), Secondary ion mass spectrometry (SIMS), Carbide formation

Abstract

________________________________

H. H. Brongersma, A. Gildenpfennig, A. W. Denier van der Gon, R. D. van de Grampel, W. P. A. Jansen, A. Knoester, J. Laven and M. M. Viitanen, (2002)

Insight in the outside: New applications of low-energy ion scattering

Abstract

________________________________

M. de Ridder, R. G. van Welzenis, H. H. Brongersma, S. Wulff, W.-F. Chu and W. Weppner, (2002)

Discovery of the rate limiting step in solid oxide fuel cells by LEIS

Abstract

________________________________

M. M. Viitanen, R. G. v. Welzenis, H. H. Brongersma and F. P. F. van Berkel, (2002)

Silica poisoning of oxygen membranes

LEIS, ISS, Ion scattering, Oxygen membranes, Perovskite, Poisoning

Abstract

________________________________

S. N. Ermolov, W. P. A. Jansen, S. N. Markin, V. G. Glebovsky and H. H. Brongersma, (2002)

The surfaces of Mo bicrystals studied by low-energy ion scattering

Low energy ion scattering (LEIS), Molybdenum, Single crystal surfaces, Surface structure, morphology, roughness, and topography, Surface segregation

Abstract

________________________________

W. P. A. Jansen, J. Beckers, J. C. v. d. Heuvel, A. W. Denier v. d. Gon, A. Bliek and H. H. Brongersma, (2002)

Dynamic Behavior of the Surface Structure of Cu/ZnO/SiO2 Catalysts

Abstract

________________________________

 

D. Farka, H. Coskun, P. Bauer, D. Roth, B. Bruckner, Petr Klapetek, N. S. Sariciftci, and P. Stadler

Increase in electron scattering length in PEDOT:PSS by a triflic acid post-processing

Monatsh Chem., 148: 5 (2017) 871-877

DOI: DOI 10.1007/s00706-017-1973-1

Transparent conductive electrodes Conductive metallic polymers Anderson localization Mott–Ioffe–Regel limit Infrared transparency

 

A stringent limitation in many optoelectronic devices, such as solar cells and light emitting diodes, is the intrinsic need for a transparent electrode. Uniting relevant aspects, indium tin oxide (ITO) is often the material of choice, however, alternatives are sought and being in particular found in conductive polymers. In this work, we present a novel doping strategy to arrive at highly conducting polymeric material based on poly-3,4-ethylenedioxythiophene (PEDOT). Based on commercial high conductivity PEDOT:PSS (Clevios PH 1000), and a post processing with aqueous triflic acid delivers a material that is both transparent and of low resistivity (5.23 × 10−4 Ω cm). Furthermore, this material retains its conductive character over a large temperature range, indicating metallic behaviour. This is further supported by positive magnetoconductance effects at low temperatures (1.8–10 K) and extended mean free paths of the conduction electrons are obse

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

D. Roth, B. Bruckner, M. V. Moro, S. Gruber, D. Goebl, J. I. Juaristi, M. Alducin, R. Steinberger, J. Duchoslav, D. Primetzhofer, and P. Bauer

Electronic Stopping of Slow Protons in Transition and Rare Earth Metals: Breakdown of the Free Electron Gas Concept

Phys. Rev. Lett., 118:  (2017) 103401

DOI: DOI: 10.1103/PhysRevLett.118.103401

TOTAL-ENERGY CALCULATIONS; AUGMENTED-WAVE METHOD; LIGHT-IONS; BASIS-SET; POWERS; IRRADIATION; GADOLINIUM; VELOCITY; SPECTRA; SOLIDS

 

The electronic stopping cross sections (SCS) of Ta and Gd for slow protons have been investigated experimentally. The data are compared to the results for Pt and Au to learn how electronic stopping in transition and rare earth metals correlates with features of the electronic band structures. The extraordinarily high SCS observed for protons in Ta and Gd cannot be understood in terms of a free electron gas model, but are related to the high densities of both occupied and unoccupied electronic states in these metals.

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

R. Coloma Ribera, R.W.E. v.d. Kruijs, J.M. Sturm, A.E. Yakshin and F. Bijkerk

Intermixing and thermal oxidation of ZrO2 thin films grown on a-Si, SiN, and SiO2 by metallic and oxidic mode magnetron sputtering

Journal of Applied Physics, 121: 11 (2017) 115303

DOI: 10.1063/1.4978367

 

The initial growth of DC sputtered ZrO2 on top of a-Si, SiN, and SiO2 layers has been studied by in vacuo high-sensitivity low energy ion scattering for two gas deposition conditions with different oxygen contents (high-O and low-O conditions). This unique surface sensitive technique allowed the determination of surface composition and thicknesses required to close the ZrO2 layer on all three substrates for both conditions. The ZrO2 layer closes similarly on all substrates due to more favorable enthalpies of formation for ZrO2 and ZrSiO4, resulting in passivation of the Si from the substrate. However, this layer closes at about half of the thickness (1.7 nm) for low-O conditions due to less oxidative conditions and less energetic particles arriving at the sample, which leads to less intermixing via silicate formation. In contrast, for high-O conditions, there is more ZrSiO4 and/or SiOx formation, giving more intermixing (3.4 nm). In vacuo X-ray photoelectron spectroscopy (XPS) measurements revealed similar stoichiometric ZrO2 layers deposited by both conditions and a higher interaction of the ZrO2 layer with the underlying a-Si for high-O conditions. In addition, oxygen diffusion through low-O ZrO2 films on a-Si has been investigated by ex situ angular-resolved XPS of samples annealed in atmospheric oxygen. For temperatures below 400 °C, no additional oxidation of the underlying a-Si was observed. This, together with the amorphous nature and smoothness of these samples, makes ZrO2 a good candidate as an oxidation protective layer on top of a-Si.

 

Contact: Universiteit Twente, Marko Sturm

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R. Steinberger, C.E. Celedón, B. Bruckner, D. Roth, J. Duchoslav, M. Arndt, P. Kürnsteiner, T. Steck, J. Faderl, C.K. Riener, G. Angeli, P. Bauer, D. Stifter

Oxygen accumulation on metal surfaces investigated by XPS, AES and LEIS, an is-sue for sputter depth profiling under UHV conditions

Appl. Surf. Sci., 411:  (2017) 189–196

DOI: doi.org/10.1016/j.apsusc.2017.03.163

XPS, AES, LEIS, Oxygen, accumulation, residual gas

 

Depth profiling using surface sensitive analysis methods in combination with sputter ion etching is a …

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

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Almeida, Rui M.; Jain, Himanshu; Pantano, Carlo G.; Mauro, J.

Low-Energy Ion-Scattering Spectroscopy of Modified Silicate Glasses.

Journal of the American Ceramic Society, :  (2016)

DOI: 10.1111/jace.14126

Glass; Depth Profiling; LEIS; Qtac; Application Paper

 

Low-Energy Ion-Scattering (LEIS) spectroscopy is a technique with a unique sensitivity to the elemental composition of the top atomic layer of a solid surface. LEIS measurements of ternary silicate glasses modified with Na2O, Cs2O, CaO, and BaO show that the compositions of the as-cast (melt) surface and the in-vacuum fracture surface often differ. While the as-cast surface is usually depleted of alkali ions (Na+ or Cs+) compared to the nominal (batch) glass composition, there is often strong accumulation of the same mobile cations on the fresh fracture surface. Depth profiles obtained by sputter etching reveal elemental concentration gradients normal to the glass surface. The final concentrations often fail to reach the nominal glass composition, suggesting the likely presence of preferential sputtering effects and thereby the distortion of the measured concentration gradient. At present, the lack of reliable standards and preferential sputtering effects in the LEIS of multicomponent glasses limit somewhat the absolute chemical composition and structural information that can be obtained with this otherwise unique and powerful method of surface analysis.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Cushman, Cody V.; Brüner, Philipp; Zakel, Julia; Major, George H.; Lunt, Barry M.; Smith, Nicholas J. et al.

Low energy ion scattering (LEIS). A practical introduction to its theory, instrumentation, and applications.

Anal. Methods, 8: 17 (2016) 3419-3439

DOI: 10.1039/c6ay00765a

LEIS; Qtac

 

Low energy ion scattering (LEIS) probes the elemental composition of the outermost atomic layer of a material and provides static depth profiles of the outer ca. 10 nm of surfaces. Its extreme surface sensitivity and quantitative nature make it a powerful tool for studying the relationships between surface chemistry and surface related phenomena such as wetting, adhesion, contamination, and thin film growth. The high depth resolution obtained in LEIS in its static and sputter depth profile modes are useful for studying the layer structures of thin films. LEIS instrumentation has improved significantly in recent years, showing dramatic increases in its sensitivity and further expanding its potential applications. In this article, we provide a practical introduction to the technique, including a discussion of the basic theory of LEIS, LEIS spectra, LEIS instrumentation, and LEIS applications, including catalysts, solid oxide fuel cells (SOFCs), and thin films in integrated circuits.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Hägglund, Carl; Grehl, Thomas; Tanskanen, Jukka T.; Yee, Ye Sheng; Mullings, Marja N.; Mackus, Adriaan J. M. et al.

Growth, intermixing, and surface phase formation for zinc tin oxide nanolaminates produced by atomic layer deposition.

J. Vac. Sci. Technol. A, 34: 2 (2016) 21516

DOI: 10.1116/1.4941411

ALD; Display Technology; Thin films; LEIS; Qtac; Multiple Techniques; Application Paper

 

A broad and expanding range of materials can be produced by atomic layer deposition at relatively low temperatures, including both oxides and metals. For many applications of interest, however, it is desirable to grow more tailored and complex materials such as semiconductors with a certain doping, mixed oxides, and metallic alloys. How well such mixed materials can be accomplished with atomic layer deposition requires knowledge of the conditions under which the resulting films will be mixed, solid solutions, or laminated. The growth and lamination of zinc oxide and tin oxide is studied here by means of the extremely surface sensitive technique of low energy ion scattering, combined with bulk composition and thickness determination, and x-ray diffraction. At the low temperatures used for deposition (150 °C), there is little evidence for atomic scale mixing even with the smallest possible bilayer period, and instead a morphology with small ZnO inclusions in a SnOx matrix is deduced. Postannealing of such laminates above 400 °C however produces a stable surface phase with a 30% increased density. From the surface stoichiometry, this is likely the inverted spinel of zinc stannate, Zn2SnO4. Annealing to 800 °C results in films containing crystalline Zn2SnO4, or multilayered films of crystalline ZnO,Zn2SnO4, and SnO2 phases, depending on the bilayer period.

 

Contact: ION-TOF, Thomas Grehl

________________________________

He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; Liu, Qingcai; Tumuluri, Uma; Wu, Zili; Wachs, Israel E.

Influence of catalyst synthesis method on selective catalytic reduction (SCR) of NO by NH3 with V2O5-WO3/TiO2 catalysts.

Applied Catalysis B, 193:  (2016) 141-150

DOI: 10.1016/j.apcatb.2016.04.022

Catalysis; Catalysts; LEIS; Qtac; Multiple Techniques; Application Paper

 

The molecular structures, surface acidity and catalytic activity for NO/NH3/O2 SCR of V2O5-WO3/TiO2 catalysts were compared for two different synthesis methods: co-precipitation of aqueous vanadium and tungsten oxide precursors with TiO(OH)2 and by incipient wetness impregnation of the aqueous precursors on a reference crystalline TiO2 support (P25; primarily anatase phase). Bulk analysis by XRD showed that co-precipitation results in small and/or poorly ordered TiO2(anatase) particles and that VOx and WOx do not form solid solutions with the bulk titania lattice. Surface analysis of the co-precipitated catalyst by High Sensitivity-Low Energy Ion Scattering (HS-LEIS) confirms that the VOx and WOx are surface segregated for the co-precipitated catalysts. In situ Raman and IR spectroscopy revealed that the vanadium and tungsten oxide components are present as surface mono-oxo O = VO3 and O = WO4 sites on the TiO2 supports. Co-precipitation was shown for the first time to also form new mono-oxo surface VO4 and WO4 sites that appear to be anchored at surface defects of the TiO2 support. IR analysis of chemisorbed ammonia showed the presence of both surface NH3* on Lewis acid sites and surface NH4+* on Brønsted acid sites. TPSR spectroscopy demonstrated that the specific SCR kinetics was controlled by the redox surface VO4 species and that the surface kinetics was independent of TiO2 synthesis method or presence of surface WO5 sites. SCR reaction studies revealed that the surface WO5 sites possess minimal activity below 325 °C and their primary function is to increase the adsorption capacity of ammonia. A relationship between the SCR activity and surface acidity was not found. The SCR reaction is controlled by the surface VO4 sites that initiate the reaction at 200 °C. The co-precipitated catalysts were always more active than the corresponding impregnated catalysts. The higher activity of the co-precipitated catalysts is ascribed to the presence of the new surface WOx sites associated surface defects on the TiO2 support that increase the ammonia adsorption capacity.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Keturakis, Christopher J.; Notis, Ben; Blenheim, Alex; Miller, Alfred C.; Pafchek, Rob; Notis, Michael R.; Wachs, Israel E.

Analysis of corrosion layers in ancient Roman silver coins with high resolution surface spectroscopic techniques.

Applied Surface Science, 376:  (2016) 241-251

DOI: 10.1016/j.apsusc.2016.03.009

LEIS; Qtac; XPS; Application Paper

 

Determination of the microchemistry of surface corrosion layers on ancient silver alloy coins is important both in terms of understanding the nature of archaeological environmental conditions to which these ancient coins were exposed and also to help in their conservation. In this present study, five ancient silver alloy coins (225 BCE–244 CE) were used as test vehicles to measure their immediate surface microchemistry and evaluate the appropriateness and limitations of High Sensitivity-Low Energy Ion Scattering Spectroscopy (HS-LEIS, 0.3 nm depth analysis), High Resolution-X-ray Photoelectron Spectroscopy (HR-XPS, 1–3 nm depth analysis) and High Resolution-Raman Spectroscopy (HR-Raman, 1000 nm depth analysis). Additional information about the deeper corrosion layers, up to 300–1000 nm, was provided by dynamic HS-LEIS and HR-Raman spectroscopy. While not archeologically significant, the use of these coins of small commercial value provides data that is more representative of the weaker signals typically obtained from ancient corroded objects, which can be in stark contrast to pristine data often obtained from carefully prepared alloys of known composition. The oldest coins, from 225 to 214 BCE, possessed an outermost surface layer containing Cu2O, Na, Al, Pb, and adsorbed hydrocarbons, while the more recent coins, from 98 to 244 CE, contained Cu2O, Ag, N, F, Na, Al, S, Cl, and adsorbed hydrocarbons in similar corresponding surface layers. It thus appears that alloying with copper, even in small amounts, leads to the formation of an outer Cu2O layer. Depth profiling revealed the presence of K, Na, Cl, and S as key corrosion components for both sets of coins with S, most likely as Ag2S, concentrated towards the surface while the Cl, most likely as AgCl, penetrated deeper. Schema to understand the overall chemistry of the corrosion layers present on these silver alloy coins were developed from the equipment limitations encountered and are presented.

 

Contact: ION-TOF, Thomas Grehl

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Longo, Roberto C.; Mattson, Eric C.; Vega, Abraham; Cabrera, Wilfredo; Cho, Kyeongjae; Chabal, Yves J.; Thissen, Peter

Mechanism of Arsenic Monolayer Doping of Oxide-Free Si(111).

Chemistry of Materials, 28: 7 (2016) 1975-1979

DOI: 10.1021/acs.chemmater.5b04394

Semiconductors; Implants; LEIS; Qtac; XPS; Application Paper

 

Density scaling and subsequent device dimension reduction continue to drive significant advances in the materials processing and architecture of advanced electronic devices.[1] As gate lengths approach the sub-10 nm regime, junction doping has become an increasing concern due to its importance in controlling short channel effects.[2] Source/drain junction depths must be extremely shallow and abrupt, typically around 1/3 of the gatelength.[3] Moreover, the transition to nonplanar architectures requires innovative methods to conformally dope the semiconductor material with fine control and reproducibility.[4] Unfortunately, the conventional techniques for junction doping, such as ion implantation and anneal [5−7] doping, [8−10] or plasma cannot produce uniform and abrupt junctions shallower than [10] nm in depth, due to fundamental broadening of dopant distribution, random dopant fluctuations, and ion induced damage.

 

Contact: ION-TOF, Thomas Grehl

________________________________

R. Coloma Ribera, R. W. E. van de Kruijs, J. M. Sturm, A. E. Yakshin, and F. Bijkerk

In vacuo growth studies of Ru thin films on Si, SiN, and SiO2 by high-sensitivity low energy ion scattering

Journal of Applied Physics, 120: 6 (2016) 065303

DOI: http://dx.doi.org/10.1063/1.4960577

surface structure, surface segregation, ion-surface impact, silicon compounds, sputter deposition, ruthenium, metallic thin films, X-ray photoelectron spectra, silicon

 

 

Contact: Universiteit Twente, Marko Sturm

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Simon R. Bare, Axel Knop-Gericke, Detre Teschner, Michael Hävacker, Raoul Blume, Tulio Rocha, Robert Schlögl, Ally S.Y. Chan, N. Blackwell, M.E. Charochak, Rik ter Veen, Hidde H. Brongersma

Surface Analysis of Zeolites: An XPS, Variable Kinetic Energy XPS, and Low Energy Ion Scattering Study

Surface Science, 648:  (2016) 376-382

DOI: 10.1016/j.susc.2015.10.048

Zeolite; XPS; X-ray photoelectron spectroscopy; low energy ion scattering spectroscopy; LEIS; catalysis

 

The surface Si/Al ratio in a series of zeolite Y samples has been obtained using laboratory XPS, synchrotron (variable kinetic energy) XPS, and low energy ion scattering (LEIS) spectroscopy. The non-destructive depth profile obtained using variable kinetic energy XPS is compared to that from the destructive argon ion bombardment depth profile from the lab XPS instrument. All of the data indicate that the near surface region of both the ammonium form and steamed Y zeolites is strongly enriched in aluminum. It is shown that when the inelastic mean free path of the photoelectrons is taken into account that the laboratory XPS of aluminosilicates zeolites does not provide a true measurement of the surface stoichiometry while using variable kinetic energy XPS a more surface sensitive measurement can be made. A comprehensive Si/Al concentration profile as a function of depth is developed by combining the data from the three surface characterization techniques. The LEIS spectroscopy reveals that the topmost atomic layer is even further enriched in Al.

 

Contact: Tascon, Rik ter Veen

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ter Veen, Rik

Statistical Quantification of LEIS Data

Tascon Technical Note, :  (2016)

DOI:

 

http://www.tascon.eu/media/en/analytical_methods/TAS-TN-Quantification_of_LEIS_data.pdf

 

Contact: Tascon, Rik ter Veen

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Brüner, Philipp; Grehl, Thomas; Brongersma, Hidde; Detlefs, Blanka; Nolot, Emmanuel; Grampeix, Helen et al

Thin film analysis by low-energy ion scattering by use of TRBS simulations.

In J. Vac. Sci. Technol. A, 33: 1 (2015) 01A122

DOI: 10.1116/1.4901451.

ALD; Semiconductors; Thin films; Data Analysis; Quantification; LEIS; Qtac; Fundamental Paper

 

Low energy ion scattering (LEIS) spectra of thin film structures are analyzed by Monte-Carlo simulations using the TRBS code. Although originally developed for the analysis of Rutherford backscattering (RBS) spectra, the TRBS code can be used to obtain valid simulations of LEIS data, which take place at energies several orders of magnitude lower than in RBS, when the appropriate adjustments are made. Experimental results from a set of Al2O3/HfO2 thin film stacks are shown, and their analysis by means of TRBS simulations is demonstrated. The authors show that the simulations yield valuable insights, especially in the case of ultrathin films <1 nm, where traditional evaluation methods using empirical models can be misleading.

 

Contact: ION-TOF, Thomas Grehl

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D. Goebl, B. Bruckner, D. Roth, C. Ahamer and P. Bauer

Low-energy ion scattering: a quantitative method?

Nucl. Instr. Meth., B354:  (2015) 3 - 8

DOI: DOI: 10.1016/j.nimb.2014.11.030

LEIS; Surface composition analysis; Information depth; Matrix effects

 

We explore under which conditions low-energy ion scattering experiments are capable of obtaining reliable quantitative results in surface composition analysis. Additionally, we elaborate on the effective information depth of this technique considering the effect of different dominant charge exchange mechanisms. Based on concrete examples, we also point out possible problems and pitfalls in the evaluation of experimental data. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

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Giraudo, Nicolas; Krolla-Sidenstein, Peter; Bergdolt, Samuel; Heinle, Marita; Gliemann, Hartmut; Messerschmidt, Florian et al.

Early Stage Hydration of Wollastonite: Kinetic Aspects of the Metal-Proton Exchange Reaction.

J. Phys. Chem. C, :  (2015) 150501094020004

DOI: 10.1021/acs.jpcc.5b02327

Qtac; MEIS; Application Paper

 

In this paper we bring up new aspects of the metal-proton exchange reaction (MPER, also called early stage hydration): (1) dependence of the number of protons consumed by the preferential exchanged cations on the pH value applied at the water/wollastonite interface and (2) strong anisotropic characteristics detected in atomic force microscopy (AFM) and low energy ion scattering spectroscopy measurements (LEIS). First we apply density functional theory (DFT) calculations to compare the kinetics of the reaction on different wollastonite surfaces and combine it with ab initio thermodynamics to set up a model describing (1) the release of Ca in exchange with H coming from the water/wollastonite interface, (2) the dependence of the MPER on the chemical potential of protons. In the second part of the paper we carried out in situ AFM and inductive coupled plasma optical emission spectroscopy (ICP-OES) measurements in order to evaluate the predicted values. While a good agreement is found in the basic and neutral regime (pH values from 14 to 4), an increasing mismatch appears in the acidic regime (pH value lower 4). This is finally explained by nonequilibrium etching, dominating over the MPER in the very acidic regime.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Illiberi, A.; Cobb, B.; Sharma, A.; Grehl, T.; Brongersma, H.; Roozeboom, F. et al.

Spatial Atmospheric Atomic Layer Deposition of InxGayZnzO for Thin Film Transistors.

ACS Appl Mater Interfaces, :  (2015)

DOI: 10.1021/am508071y

ALD; Complex Oxides; Display Technology; Thin films; LEIS; Qtac; Application Paper

 

We have investigated the nucleation and growth of InGaZnO thin films by spatial atmospheric atomic layer deposition. Diethyl zinc (DEZ), trimethyl indium (TMIn), triethyl gallium (TEGa), and water were used as Zn, In, Ga and oxygen precursors, respectively. The vaporized metal precursors have been coinjected in the reactor. The metal composition of InGaZnO has been controlled by varying the TMIn or TEGa flow to the reactor, for a given DEZ flow and exposure time. The morphology of the films changes from polycrystalline, for ZnO and In-doped ZnO, to amorphous for In-rich IZO and InGaZnO. The use of these films as the active channel in TFTs has been demonstrated and the influence of In and Ga cations on the electrical characteristics of the TFTs has been studied.

 

Contact: ION-TOF, Thomas Grehl

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Longo, Roberto C.; Cho, Kyeongjae; Brüner, Philipp; Welle, Alexander; Gerdes, Andreas; Thissen, Peter

Carbonation of wollastonite(001) competing hydration: microscopic insights from ion spectroscopy and density functional theory.

ACS Appl Mater Interfaces, 7: 8 (2015) 4706-4712

DOI: 10.1021/am508313g

LEIS; Qtac; Application Paper

 

In this paper, we report about the influence of the chemical potential of water on the carbonation reaction of wollastonite (CaSiO3) as a model surface of cement and concrete. Total energy calculations based on density functional theory combined with kinetic barrier predictions based on nudge elastic band method show that the exposure of the water-free wollastonite surface to CO2 results in a barrier-less carbonation. CO2 reacts with the surface oxygen and forms carbonate (CO3(2-)) complexes together with a major reconstruction of the surface. The reaction comes to a standstill after one carbonate monolayer has been formed. In case one water monolayer is covering the wollastonite surface, the carbonation is no more barrier-less, yet ending in a localized monolayer. Covered with multilayers of water, the thermodynamic ground state of the wollastonite completely changes due to a metal-proton exchange reaction (also called early stage hydration) and Ca(2+) ions are partially removed from solid phase into the H2O/wollastonite interface. Mobile Ca(2+) reacts again with CO2 and forms carbonate complexes, ending in a delocalized layer. By means of high-resolution time-of-flight secondary-ion mass spectrometry images, we confirm that hydration can lead to a partially delocalization of Ca(2+) ions on wollastonite surfaces. Finally, we evaluate the impact of our model surface results by the meaning of low-energy ion-scattering spectroscopy combined with careful discussion about the competing reactions of carbonation vs hydration.

 

Contact: ION-TOF, Thomas Grehl

________________________________

M. Dosmailov, L.N. Leonat, J. Patek, D. Roth, P. Bauer, M.C. Scharber, N.S. Sariciftci, J.D. Pedarnig

Transparent conductive ZnO layers on polymer substrates: thin film deposition and application in organic solar cells

Thin Solid Films, 591:  (2015) 97 – 104

DOI: DOI: 10.1016/j.tsf.2015.08.015

Transparent conductive zinc oxide; Polymer substrate; Polyethylene terephthalate; Pulsed-laser deposition; Rutherford back scattering analysis; Organic solar cells

 

Aluminum doped ZnO (AZO) and pure ZnO thin films are grown on polymer substrates by pulsed-laser deposition and the optical, electrical, and structural film properties are investigated. Laser fluence, substrate temperature, and oxygen pressure are varied to obtain transparent, conductive, and stoichiometric AZO layers on polyethylene terephthalate (PET) that are free of cracks. At low fluence (1 J/cm(2)) and low pressure (10(-3) mbar), AZO/PET samples of high optical transmission in the visible range, low electrical sheet resistance, and high figure of merit (FOM) are produced. AZO films on fluorinated ethylene propylene have low FOM. The AZO films on PET substrates are used as electron transport layer in inverted organic solar cell devices employing P3HT:PCBM as photovoltaic polymer-fullerene bulk heterojunction. (C) 2015 Elsevier B.V. All rights reserved.

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

P.J. van Zwol, D.F. Vles, W.P. Voorthuijzen, M. Péter, H. Vermeulen, W.J. van der Zande, J.M. Sturm, R.W.E. van de Kruijs and F. Bijkerk

Emissivity of freestanding membranes with thin metal coatings,

Journal of Applied Physics, 118:  (2015) 213107

DOI: 10.1063/1.4936851

Extreme UV lithography, pellicles, emissivity, metal coatings

 

Freestanding silicon nitride membranes with thicknesses down to a few tens of nanometers find use

as TEM windows or soft X-ray spectral purity filters. As the thickness of a membrane decreases,

emissivity vanishes, which limits radiative heat emission and resistance to heat loads. We show

that thin metal layers with thicknesses in the order of 1 nm enhance the emissivity of thin membranes

by two to three orders of magnitude close to the theoretical limit of 0.5. This considerably

increases thermal load capacity of membranes in vacuum environments. Our experimental results

are in line with classical theory in which we adapt thickness dependent scattering terms in the

Drude and Lorentz oscillators.

 

 

Contact: Universiteit Twente, Marko Sturm

________________________________

Rupp, Ghislain M.; Téllez, Helena; Druce, John; Limbeck, Andreas; Ishihara, Tatsumi; Kilner, John; Fleig, Jürgen

Surface chemistry of La 0.6 Sr 0.4 CoO 3−δ thin films and its impact on the oxygen surface exchange resistance.

J. Mater. Chem. A, 3: 45 (2015) 22759-22769

DOI: 10.1039/c5ta05279c

Ceramics; Fuel Cells; LEIS; Qtac; Application Paper

 

The surface composition of dense La0.6Sr0.4CoO3−δ (LSC) thin film model electrodes, deposited by pulsed laser deposition at 600 °C on yttria-stabilized zirconia (100) electrolytes, was investigated by low-energy ion scattering (LEIS) and time resolved inductively coupled plasma mass spectrometry (ICP-MS). Results obtained by both methods agree qualitatively and quantitatively and provide a comprehensive picture of the surface composition and cation diffusion kinetics of LSC. The measurements revealed that freshly prepared LSC thin films already show a Sr-rich and Co-poor termination layer (80% Sr surface coverage). This Sr-rich surface layer was proven to be an equilibrium property of LSC as it forms again at elevated temperatures after removal. The kinetics of this surface reconstruction is surprisingly fast (<1 h at 550 °C) and indicates high Sr mobility in LSC. Electrochemical Impedance Spectroscopy (EIS) measurements at 400 °C revealed the detrimental effect of this surface layer on the oxygen surface exchange and suggest that higher Co concentrations in the termination layer facilitate the oxygen exchange reaction.

 

Contact: ION-TOF, Thomas Grehl

________________________________

S. Prusa, P. Prochazka, P. Babor, T. Sikola, R. ter Veen, M. Fartmann, T. Grehl, Ph. Brüner, D. Roth, P. Bauer, H.H. Brongersma

Highly Sensitive Detection of Surface and Intercalated Impurities in Graphene by LEIS

Langmuir, 31: 35 (2015) 9628-6935

DOI: 10.1021/acs.langmuir.5b01935

Carbon Graphene LEIS

 

Low-energy ion scattering (LEIS) is known for its extreme surface sensitivity, as it yields a quantitative analysis of the outermost surface as well as highly resolved in-depth information for ultrathin surface layers. Hence, it could have been generally considered to be a suitable technique for the analysis of graphene samples. However, due to the low scattering cross section for light elements such as carbon, LEIS has not become a common technique for the characterization of graphene. In the present study we use a high-sensitivity LEIS instrument with parallel energy analysis for the characterization of CVD graphene transferred to thermal silica/silicon substrates. Thanks to its high sensitivity and the exceptional depth resolution typical of LEIS, the graphene layer closure was verified, and different kinds of contaminants were detected, quantified, and localized within the graphene structure. Utilizing the extraordinarily strong neutralization of helium by carbon atoms in graphene, LEIS experiments performed at several primary ion energies permit us to distinguish carbon in graphene from that in nongraphitic forms (e.g., the remains of a resist). Furthermore, metal impurities such as Fe, Sn, and Na located at the graphene–silica interface (intercalated) are detected, and the coverages of Fe and Sn are determined. Hence, high-resolution LEIS is capable of both checking the purity of graphene surfaces and detecting impurities incorporated into graphene layers or their interfaces. Thus, it is a suitable method for monitoring the quality of the whole fabrication process of graphene, including its transfer on various substrates.

 

Contact: Tascon, Rik ter Veen

________________________________

Symianakis, Emmanouil; Malko, Daniel; Ahmad, Ehsan; Mamede, Anne-Sophie; Paul, Jean-Francois; Harrison, Nicholas; Kucernak, Anthony

Electrochemical Characterization and Quantified Surface Termination Obtained by Low Energy Ion Scattering and X-ray Photoelectron Spectroscopy of Orthorhombic and Rhombohedral LaMnO3 Powders.

J. Phys. Chem. C, 119: 22 (2015) 12209-12217

DOI: 10.1021/acs.jpcc.5b02742

Catalysis; Catalysts; Ceramics; Fuel Cells; LEIS; Qtac; XPS; Application Paper

 

LaMnO3 powder synthesized by glycine combustion synthesis with the rhombohedral and orthorhombic structures has been characterized by the combination of low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS), while the electrocatalytic activity for the oxygen reduction reaction is measured with the rotating disk electrode (RDE) method. Quantification of the surface terminations obtained by LEIS suggests that the orthorhombic LaMnO3 crystallites are near thermodynamic equilibrium as surface atomic ratios compare well with those of equilibrium morphologies computed by a Wulff construction based on computed surface energies. Both rhombohedral and orthorhombic structures present the same La/Mn atomic ratio on the surface. Electrochemical activity of the two structures is found to be the same within the error bar of our measurements. This result is in disagreement with results previously reported on the activity of the two structures obtained by the coprecipitation method [Suntivich et al. Nat. Chem. 2011, 3 (7), 546], and it indicates that the preparation method and the resulting surface termination might play a crucial role for the activity of perovskite catalysts.

 

Contact: ION-TOF, Thomas Grehl

________________________________

T.M.C. Hoang, B. Geerdink, J.M. Sturm, L. Lefferts and K. Seshan

Steam reforming of acetic acid - A major component in the volatiles formed during gasification of humin

Appl. Catal. B: Environmental 163, 74 (2015), 163:  (2015) 74

DOI: 10.1016/j.apcatb.2014.07.046

Steam reforming, Acetic acid, Humin, Nickel, Ceria–zirconia

 

Acetic acid and phenols are the major components of the condensable by-products in the low temperaturede-volatilisation stage of humin during gasification. Catalytic steam reforming of acetic acid using sup-ported Ni on ceria-zirconia mixed oxide prepared via the hydrothermal route is discussed. The influenceof steam reforming temperatures, steam/carbon ratios were studied. The catalyst showed high activityand good stability. Furthermore, activity improvement was achieved with multiple redox cycles as rele-vant to recycling the catalysts. Characterisation of the fresh and used catalyst by various techniques (e.g.,LEIS, Raman spectroscopy, TPO/TPR) revealed the modification of metal-oxygen bond on the supportunder the steam reforming conditions. It in turn improved the oxygen mobility of the catalyst.

 

Contact: Universiteit Twente, Marko Sturm

________________________________

Villar-Garcia, Ignacio J.; Fearn, Sarah; Ismail, Nur L.; McIntosh, Alastair J S; Lovelock, Kevin R J

Fine tuning the ionic liquid-vacuum outer atomic surface using ion mixtures.

Chemical communications (Cambridge, England), 51: 25 (2015) 5367-5370

DOI: 10.1039/c4cc06307d

Ionic Liquids; LEIS; Qtac; Application Paper

 

Ionic liquid-vacuum outer atomic surfaces can be created that are remarkably different from the bulk composition. In this communication we demonstrate, using low-energy ion scattering (LEIS), that for ionic liquid mixtures the outer atomic surface shows significantly more atoms from anions with weaker cation-anion interactions (and vice versa).

 

Contact: ION-TOF, Thomas Grehl

________________________________

Chen, Guangxu; Zhao, Yun; Fu, Gang; Duchesne, Paul N.; Gu, Lin; Zheng, Yanping et al.

Interfacial effects in iron-nickel hydroxide-platinum nanoparticles enhance catalytic oxidation. INCLUDING SUPPLEMENTAL MATERIAL.

Science (New York, N.Y.), 344: 6183 (2014) 495-499

DOI: 10.1126/science.1252553

Catalysis; Catalysts; Nanoparticles; LEIS; Qtac; Multiple Techniques; Application Paper

 

Hybrid metal nanoparticles can allow separate reaction steps to occur in close proximity at different metal sites and accelerate catalysis. We synthesized iron-nickel hydroxide-platinum (transition metal-OH-Pt) nanoparticles with diameters below 5 nanometers and showed that they are highly efficient for carbon monoxide (CO) oxidation catalysis at room temperature. We characterized the composition and structure of the transition metal-OH-Pt interface and showed that Ni(2+) plays a key role in stabilizing the interface against dehydration. Density functional theory and isotope-labeling experiments revealed that the OH groups at the Fe(3+)-OH-Pt interfaces readily react with CO adsorbed nearby to directly yield carbon dioxide (CO2) and simultaneously produce coordinatively unsaturated Fe sites for O2 activation. The oxide-supported PtFeNi nanocatalyst rapidly and fully removed CO from humid air without decay in activity for 1 month.

 

Contact: ION-TOF, Thomas Grehl

________________________________

D. Goebl, W. Roessler, D. Roth, and P. Bauer

Influence of the excitation threshold of d electrons on electronic stopping of slow light ions

Phys. Rev., A90: 4 (2014) 42706

DOI: DOI: 10.1103/PhysRevA.90.042706

ENERGY NE+ SCATTERING; D-BAND METALS; CROSS-SECTIONS; CHARGE-EXCHANGE; PHOTOEMISSION SPECTRA; SURFACE SCATTERING; GAS; POWER; VELOCITY; AL

 

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

D. Primetzhofer, M. Sytnyk, P. J. Wagner, P. Bauer, W. Heiss

The potential of Rutherford Backscattering Spectrometry for composition analysis of colloidal nanocrystals

Nucl. Instr. Meth., B332:  (2014) 122

DOI: http://dx.doi.org/10.1016/j.nimb.2014.02.043

RBS; Elastic scattering; Nanocrystal; Cation-exchange

 

We investigate the potential of elastic scattering of energetic ions for compositional analysis of magnetic colloidal nanocrystals. Thin layers of nanocrystals deposited by spin coating on Si-wafers are investigated by two different set-ups for Rutherford Backscattering Spectrometry (RBS), employing different projectile ions (He-4, C-12) and primary energies (600 keV-8 MeV). The advantages and disadvantages of the different approaches are discussed in terms of obtainable mass resolution, necessary primary particle fluence and deposited energy. It is shown that different isotopes of transition metals can be resolved by employing 8 MeV C-12(3+) primary ions.

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

Druce, John; Ishihara, Tatsumi; Kilner, John

Surface composition of perovskite-type materials studied by Low Energy Ion Scattering (LEIS).

Solid State Ionics, 262:  (2014) 893-896

DOI: 10.1016/j.ssi.2013.09.010

Ceramics; Complex Oxides; Fuel Cells; LEIS; Qtac; Application Paper

 

The analysis of the surface chemistry of electrodematerials for solid oxide electrochemical conversion devices is of great importance to understand the fundamental mechanism of the oxygen exchange reaction, and the influence of changes in surface chemistry ondevice degradation. LowEnergy Ion Scattering (LEIS) is anextremely surface sensitive analysis technique, capable of probing this chemistry in the very outer atomic layer of a material under conditions relevant to its operational state. In this contribution,weuse LEIS to study the Sr segregation process in the perovskite La0.6Sr0.4Co0.2Fe0.8O3 − δ (LSCF), and show that, conversely, there is no segregation of either lanthanide cation in Ruddlesden–Popper structured Pr1La1NiO4+ δ (PLNO).

 

Contact: ION-TOF, Thomas Grehl

________________________________

Druce, John; Simrick, Neil; Ishihara, Tatsumi; Kilner, John

“Imaging” LEIS of micro-patterned solid oxide fuel cell electrodes.

Nuclear Instruments and Methods in Physics Research B, 332:  (2014) 261-265

DOI: 10.1016/j.nimb.2014.02.074

Ceramics; Complex Oxides; Fuel Cells; Imaging; LEIS; Qtac; Application Paper

 

Understanding the kinetics of oxygen exchange between the gas phase and a ceramic electrode is key to optimising the performance of electrochemical energy conversion devices such as Solid Oxide Fuel Cells. Clearly the surface chemistry of these materials is important, and surface sensitive techniques such as electrode kinetics. In this work, we use high lateral resolution LEIS to perform local analyses of a micropatterned electrode structure, of the type often used for studies of the geometrical dependences of electrode performance. We find that the results are comparable to those for bulk materials, but detect evidence of cation interdiffusion from the electrode to the electrolyte. Finally, we note that this preliminary study could open the prospect of in situ measurements of cells near operating conditions.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Druce, John; Téllez, Helena; Simrick, Neil; Ishihara, Tatsumi; Kilner, John

Surface composition of solid oxide electrode structures by laterally resolved low energy ion scattering (LEIS).

International Journal of Hydrogen Energy., :  (2014)

DOI: 10.1016/j.ijhydene.2014.07.005

Fuel Cells; Imaging; LEIS; Qtac; Application Paper

 

Low Energy Ion Scattering (LEIS) is a powerful tool to analyse the composition of the very outermost atomic monolayer of a material. However, most studies so far have been conducted on ceramic pellets of the materials of interest. In this work, we apply laterally resolved LEIS analysis to electrochemical cells consisting of micro-patterned arrays of LSCF electrodes on YSZ electrolytes. The results suggest the migration of constituent elements and impurities between the two phases which has the potential to influence device performance.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Erkens, Ivo J. M.; Verheijen, Marcel A.; Knoops, Harm C. M.; Landaluce, Tatiana F.; Roozeboom, Fred; Kessels, Wilhelmus M. M.

Plasma-Assisted Atomic Layer Deposition of PtO x from (MeCp)PtMe 3 and O 2 Plasma.

Chem. Vap. Deposition, 20: 7-8-9 (2014) 258-268

DOI: 10.1002/cvde.201407109

ALD; Thin Film Deposition; Thin films; LEIS; Qtac; Application Paper

 

Atomic layer deposition (ALD) using (MeCp)PtMe3 and O2 gas or O2 plasma is a well-established technique for the deposition of thin films of Pt, but the potential of ALD to deposit platinum oxide (PtOx) has not yet been systematically explored. This work demonstrates how PtOx can be deposited by plasma-assisted (PA)-ALD in a temperature window from room temperature (RT) to 300 °C by controlling the O2 plasma and (MeCp)PtMe3 exposure. With increasing substrate temperature, the thermal stability of PtOx decreases and the reducing activity of the precursor ligands increases. Therefore, longer O2 plasma exposures and/or lower (MeCp)PtMe3 exposures are required to obtain PtOx at higher temperatures. Furthermore, it is established that, during the nucleation stage, PtOx ALD starts by the formation of islands that grow and coalesce during the initial 40 cycles. Closed-layer thin films of PtOx with an O/Pt ratio of 2.5 can be deposited at 100 °C with a minimal thickness of only 2 nm. It is also demonstrated that a conformality of 90% can be reached for PtOx films in trenches with an aspect ratio of 9 when using optimized O2 plasma and precursor exposure times.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Ignacio J. Villar-Garcia, Sarah Fearn, Gilbert F. De Gregorio, Nur L. Ismail, Florence J. V. Gschwend, Alastair J. S. McIntosh and Kevin R. J. Lovelock

 

The ionic liquid - vacuum outer atomic surface: a low-energy ion scattering study

Chem. Sci., :  (2014)

DOI: 10.1039/c4sc00640b

LEIS ionic liquids

 

We have identified elements present in the ionic liquid – vacuum outer atomic surface of 23 ionic liquids using high sensitivity low-energy ion scattering (LEIS), a very surface sensitive technique. We show that the probability of cationic heteroatoms being present at the ionic liquid – vacuum outer atomic surface is very low; we detected imidazolium nitrogen for only one of the 18 imidazolium based ionic liquids investigated, no nitrogen for the two ammonium based ionic liquids and a very small amount of phosphorus for two of the three phosphonium-based ionic liquids. We determine that the anion is always present at the ionic liquid – vacuum outer atomic surface, even for very large cations containing dodecyl alkyl chains or longer; these chains dominate the ionic liquid – vacuum outer atomic surface, but are not sufficiently densely packed to completely cover the anions. We demonstrate the presence of strong hydrogen bond acceptor adsorption sites at the ionic liquid – vacuum outer atomic surface. We demonstrate that the amount of ion present at the ionic liquid – vacuum outer atomic surface can be tuned by varying the size of the other ion; larger cations (or anions) occupy more of the ionic liquid – vacuum outer atomic surface, leaving less room for anions (or cations). By identifying elements present at the ionic liquid – vacuum outer atomic surface, conclusions can be drawn on the orientations of anions nearest the vacuum. We show that for five different anions there is a most probable ion orientation, but other anion orientations also exist, demonstrating the presence of multiple anion orientations. The imidazolium cations nearest to the vacuum also show similar multi-orientation behaviour. This variety of atoms present and therefore ion orientations is expected to be central to controlling surface reactivity. In addition, our results can be used to quantitatively validate simulations of the ionic liquid – vacuum surface at a molecular level. Overall, our studies, in combination with literature data from different techniques and simulations, provide a clear picture of ionic liquid – vacuum outer atomic surfaces.

 

Contact: Tascon, Rik ter Veen

________________________________

Téllez, Helena; Aguadero, Ainara; Druce, John; Burriel, Mónica; Fearn, Sarah; Ishihara, Tatsumi et al.

New perspectives in the surface analysis of energy materials by combined time-of-flight secondary ion mass spectrometry (ToF-SIMS) and high sensitivity low-energy ion scattering (HS-LEIS).

Journal of Analytical Atomic Spectrometry, 29: 8 (2014) 1361

DOI: 10.1039/c3ja50292a

Ceramics; Fuel Cells; LEIS; Qtac; TOF-SIMS; Application Paper

 

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and low-energy ion scattering (LEIS) are recently attracting great interest in energy materials research due to their capabilities in terms of surface sensitivity and specificity, spatial resolution and their ability to analyse the isotopic chemical composition. This work shows the synergy provided by this powerful combination to further our understanding of the surface chemistry and structure that ultimately determines the electrochemical performance in advanced electro-ceramic materials for energy storage and energy conversion applications. In particular, this novel approach has been applied to the analysis of (Li3xLa2/3 x, 1/3 2x)TiO3 perovskite materials used as the electrolyte in lithium batteries and (La, Sr)2CoO4+ d epitaxial thin films used as oxygen electrodes in solid oxide fuel cells and solid oxide electrolysers. The analysis of these two promising materials requires the development and optimisation of new analytical approaches that take advantage of the recent instrumental developments in order to characterise the outermost and near-surfaces at the atomic scale.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Téllez, Helena; Druce, John; Hall, Allen; Ishihara, Tatsumi; Kilner, John; Rockett, Angus

Low energy ion scattering: surface preparation and analysis of Cu(In,Ga)Se 2 for photovoltaic applications.

Prog. Photovolt: Res. Appl., 23: 10 (2014) 1219-1227

DOI: 10.1002/pip.2535

Photovoltaics; LEIS; Qtac; Application Paper

 

Cu(In,Ga)Se2 (CIGS) single-crystal epitaxial films have been analyzed by low energy ion scattering, which is sensitive to exactly the outermost surface atomic layer, to determine the surface chemistry as a function of preparation conditions. The samples were grown by a hybrid sputtering and evaporation method on cation (A) or anion (B) terminated (111) GaAs substrates and had smooth surfaces. The samples were exposed to excited atomic oxygen or hydrogen beams or were sputtered with 500 eV Ar+ ions. Atomic O* treatment resulted in an otherwise clean, oxidized surface including all film constituents. Atomic H* resulted in strong enhancement of the surface Ga population, probably due to a preexisting Ga native oxide in the outermost atomic layer. Sputtering produced a clean surface that was closest to the bulk composition of the film as measured by energy-dispersive spectroscopy.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Téllez, Helena; Druce, John; Ju, Young-Wan; Kilner, John; Ishihara, Tatsumi

Surface chemistry evolution in LnBaCo2O5 + δ double perovskites for oxygen electrodes.

International Journal of Hydrogen Energy, 39: 35 (2014)

DOI: 10.1016/j.ijhydene.2014.06.102

Ceramics; Complex Oxides; Fuel Cells; LEIS; Qtac;  Multiple Techniques; Application Paper

 

The electro-catalytically active surfaces of mixed ionic electronic conductors (MIECs) are critically important for the operation of electrochemical devices such as solid oxide electrolyser cells (SOECs) and fuel cells (SOFCs). However, the composition and morphology of surfaces of real samples are often poorly characterized, and thus our understanding of the influence of these factors on the surface exchange reactions is rudimentary. In this work, we apply low energy ion scattering (LEIS) spectrometry and atomic force microscopy (AFM) to investigate the evolution of the surface composition and morphology of two layered perovskite type materials, showing the dynamic nature of these surfaces even at room temperature.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Villar-Garcia, Ignacio J.; Fearn, Sarah; De Gregorio, Gilbert F.; Ismail, Nur L.; Gschwend, Florence J. V.; McIntosh, Alastair J. S.; Lovelock, Kevin R. J.

The ionic liquid–vacuum outer atomic surface: a low-energy ion scattering study.

Chem. Sci., 5: 11 (2014) 4404-4418

DOI: 10.1039/c4sc00640b

Ionic Liquids; LEIS; Qtac; Application Paper

 

We have identified elements present in the ionic liquid–vacuum outer atomic surface of 23 ionic liquids using high sensitivity low-energy ion scattering (LEIS), a very surface sensitive technique. We show that the probability of cationic heteroatoms being present at the ionic liquid–vacuum outer atomic surface is very low; we detected imidazolium nitrogen for only one of the 18 imidazolium based ionic liquids investigated, no nitrogen for the two ammonium based ionic liquids and a very small amount of phosphorus for two of the three phosphonium-based ionic liquids. We determine that the anion is behaviour. This variety of atoms present and therefore ion orientations is expected to be central to controlling surface reactivity. In addition, our results can be used to quantitatively validate simulations of the ionic liquid–vacuum surface at a molecular level. Overall, our studies, in combination with literature data from different techniques and simulations, provide a clear picture of ionic liquid–vacuum outer atomic surfaces.

 

Contact: ION-TOF, Thomas Grehl

________________________________

M.Sytnyk, R. Kirchschlager, M.I. Bodnarchuk, D. Primetzhofer, D. Kriegner, H. Enser, J. Stangl, P. Bauer, M. Voith, A.W. Hassel, F. Krumeich, F. Ludwig, A. Meingast, G. Kothleitner, M.V. Kovalenko, W. Heiss,

Tuning the Magnetic Properties of Metal Oxide Nanocrystal Heterostructures by Cation Exchange

Nano letters, 13:  (2013) 586

DOI: dx.doi.org/10.1021/nl304115r | NanoLett. 2013, 13, 586 − 593

magnetic nanocrystals, cation exchange, exchange bias, nanoheterostructures, ferrites

 

For three types of colloidal magnetic nanocrystals, we demonstrate that postsynthetic cation exchange enables tuning of the nanocrystal’s magnetic properties and achieving characteristics not obtainable by conventional synthetic routes. While the cation exchange procedure, performed in solution phase approach, was restricted so far to chalcogenide based semiconductor nanocrystals, here ferrite-based nanocrystals were subjected to a Fe2+ to Co2+ cation exchange procedure. This allows tracing of the compositional modifications by systematic and detailed magnetic characterization. In homogeneous magnetite nanocrystals and in gold/magnetite core shell nanocrystals the cation exchange increases the coercivity field, the remanence magnetization, as well as the superparamagnetic blocking temperature.

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

Brongersma, Hidde H.; Brüner, Philipp; Grehl, Thomas; ter Veen, Henrik R. J.; Bauer, Peter; van den Berg, Jaap A. et al.

High Resolution In-Depth Analysis with Low-Energy Ion Scattering: Experiments and Simulation.

Proceedings of the XXI International Conference on Ion-Surface Interactions (ISI 2013), Yaroslavl, Russia, :  (2013) 245–249

DOI:

LEIS; Qtac; Review Paper

 

Low-Energy Ion Scattering (LEIS) is well known for its extreme surface sensitivity. Using nobel gas ions (He+, Ne+, Ar+, Kr+; 0.5 - 10 keV) the atomic composition of the outer atomic layer of a sample can be quantified. For high sensitivity and high mass resolution instruments the detcetion limit is typically a few at. % (light elements) to 10 ppm (heaviest elements) of 1 monolayer [1,2,3]. the unique surface sensitivity has led to new insight in materials like catalysts, semiconductors, ceramics, polymers, graphene [4] and to applications [1] like nanoclusters, biosensors, isotopic exchange [5], dental implants [6] and surface modification.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Burriel, Mónica; Wilkins, Stuart; Hill, John P.; Muñoz-Márquez, Miguel A.; Brongersma, Hidde H.; Kilner, John A. et al.

Absence of Ni on the outer surface of Sr doped La2NiO4 single crystals.

Energy Environ. Sci., 7: 1 (2013) 311

DOI: 10.1039/c3ee41622d

Complex Oxides; Single Crystals; LEIS; Qtac; XPS; Application Paper

 

A combination of surface sensitive techniques was used to determine the surface structure and chemistry of La2−xSrxNiO4+δ. These measurements unequivocally showed that Ni is not present in the outermost atomic layer, suggesting that the accepted model with the B-site cations exposed to the environment is incorrect.

 

Contact: ION-TOF, Thomas Grehl

________________________________

D. Goebl, D. Primetzhofer, E. Abad, R. C. Monreal and P. Bauer

Auger neutralization of He+ on Cu surfaces: simulation of azimuthal scans

Nucl. Instr. Meth. B, 317:  (2013) 23

DOI: https://doi.org/10.1016/j.nimb.2012.12.090

LEIS, Charge exchange, Auger-neutralization, Ion fraction, Cun surfaces

 

Charge exchange by Auger neutralization (AN) plays an important role in surface analysis techniques such as low energy ion scattering (LEIS). Recent advances in the theoretical description of AN have included a model based on a linear combination of atomic orbitals (LCAO) approach, which is able to calculate accurate neutralization probabilities of He+ due to AN in LEIS. Previous investigations have shown that the neutralization probability is strongly influenced by the distance dependent shift of the He 1s level. In this study simulations of He+ scattered from Cu(1 0 0) and Cu(1 1 0) surfaces at fixed azimuth angles are presented. Additionally, the azimuth dependence of ion- and neutral-yield for He+ scattered from Cu(1 0 0) is simulated and compared to experimental data. Calculations were performed using the LCAO model in combination with molecular dynamics simulations. The excellent agreement between simulation and experiment provides evidence that the obtained values for the level shift are a characteristic property of the surface.

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

D. Goebl, D. Roth, D. Primetzhofer, A. Putz and P. Bauer

Quasi-resonant neutralization of He+ ions at a Germanium surface

J. Phys.: Condens. Matter, 25:  (2013) 485006

DOI: doi:10.1088/0953-8984/25/48/485006

 

When low-energy He ions are scattered from a Ge surface, the fraction of positive ions exhibits characteristic oscillations as a function of ion energy. These oscillations are caused by quasi-resonant neutralization (qRN), a process which is active for materials with a narrow band nearly resonant with the unperturbed He 1s-level. In this paper we measure the fraction of He+ backscattered from Ge(100). In conjunction with recently developed theoretical methods, we extract quantitative information on the efficiency of qRN. Our evaluation reveals that qRN is a highly efficient process leading to ion fractions two orders of magnitude lower than in systems for which neutralization is only due to Auger processes.

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

Kauling, Alan; Ebeling, Günter; Morais, Jonder; Pádua, Agílio; Grehl, Thomas; Brongersma, Hidde H.; Dupont, Jairton

Surface composition/organization of ionic liquids with Au nanoparticles revealed by high-sensitivity low-energy ion scattering.

Langmuir, 29: 46 (2013) 14301-14306

DOI: 10.1021/la403388b

Ionic Liquids; Nanoparticles; LEIS; Qtac; Application Paper

 

High-sensitivity low-energy ion scattering (HS-LEIS) analysis was used to elucidate the outermost layer of both functionalized and non-functionalized imidazolium ionic liquids (ILs). The IL outermost layer is composed of all atoms of both cations and anions. The HS-LEIS analyses also allow for quantitative measurement of the thickness of IL overlayers on Au nanoparticles prepared by sputter deposition, which was shown to be a monolayer of ions, as predicted by density functional theory calculations.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Kersting, R.; Breitenstein, D.; Hagenhoff, B.; Fartmann, M.; Heller, D.; Grehl, T. et al.

Surface characterization of nanoparticles: different surface analytical techniques compared. SIMS XVIII Proceedings.

Surface and Interface Analysis, 45: 1 (2013) 503-505

DOI: 10.1002/sia.5117

Application paper LEIS TOF-SIMS Multiple techniquesThin film deposition (PVD, CVD)

 

The rapidly growing interest in nanoparticles (NPs) as part of technical products conflicts with the limited knowledge about potential health risks. This dilemma is the initial point of the project NanoPaCT where, based on the chemical composition of NPs and toxicological tests, a forecast on their biological activity should be made. For the chemical characterization of the outer surface of core-shell NPs, an excellent surface sensitivity of the applied analytical techniques is required. In this article, we will present data on an approach to optimise time-of-flight secondary ion mass spectrometry (ToF-SIMS) to this need. The effect of primary ion parameters (species, energy) was studied on a model system (HfO2 on Si) as well as on Lumidot core-shell NPs. The full layer closure of both films was proofed by means of low energy ion scattering. On the flat high-K sample, a clear variation of surface sensitivity could be observed as function of primary ion (PI) parameters. In contrast to this, almost no effect was found on core-shell NPs which behave in the experiment like homogeneous particles. These results indicate that NPs probably melt-up or evaporate after direct or grazing impact of PI at typical energies used in ToF-SIMS.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Phivilay, Somphonh P.; Puretzky, Alexander A.; Domen, Kazunari; Wachs, Israel E.

Nature of Catalytic Active Sites Present on the Surface of Advanced Bulk Tantalum Mixed Oxide Photocatalysts.

ACS Catalysis, 3: 12 (2013) 2920-2929

DOI: 10.1021/cs400662m

Catalysis; Catalysts; LEIS; Qtac; Multiple Techniques; Application Paper

 

The most active photocatalyst system for water splitting under ultraviolet (UV) irradiation (270 nm) is the promoted 0.2% NiO/NaTaO3:2% La photocatalyst with an optimized photonic efficiency of 56%, but fundamental issues about the nature of the surface catalytic active sites and their involvement in the photocatalytic process still need to be clarified. This is the first study to apply cutting-edge surface spectroscopic analyses to determine the surface nature of tantalum mixed oxide photocatalysts. Surface analysis with high-resolution X-ray photoelectron spectroscopy (1–3 nm) and high-sensitivity low-energy ion scattering spectroscopy (0.3 nm) indicates that the NiO and La2O3 promoters are concentrated in the surface region of the bulk NaTaO3 phase. The NiO is concentrated on the NaTaO3 outermost surface layers, while La2O3 is distributed throughout the NaTaO3 surface region (1–3 nm). Raman and UV–vis spectroscopy revealed that the bulk molecular and electronic structures, respectively, of NaTaO3 were not modified by the addition of the La2O3 and NiO promoters, with La2O3 resulting in a slightly more ordered structure. Photoluminescence spectroscopy reveals that the addition of La2O3 and NiO produces a greater number of electron traps resulting in the suppression of the recombination of excited electrons and holes. In contrast to earlier reports, La2O3 is only a textural promoter (increasing the BET surface area by 7-fold by stabilizing smaller NaTaO3 particles) and causes an 3-fold decrease in the specific photocatalytic TORs (micromoles of H2 per square meter per hour) rate because surface La2O3 blocks exposed catalytic active NaTaO3 sites. The NiO promoter was found to be a potent electronic promoter that enhances the NaTaO3 surface-normalized TORs by a factor of 10–50 and turnover frequency by a factor of 10. The level of NiO promotion is the same in the absence and presence of La2O3, demonstrating that there is no promotional synergistic interaction between the NiO and La2O3 promoters. This study demonstrates the important contributions of the photocatalyst surface properties to the fundamental molecular/electronic structure–photoactivity relationships of promoted NaTaO3 photocatalysts that were previously not appreciated in the literature.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Phivilay, Somphonh P.; Roberts, Charles A.; Puretzky, Alexander A.; Domen, Kazunari; Wachs, Israel E.

Fundamental Bulk/Surface Structure–Photoactivity Relationships of Supported (Rh 2– y Cr y O 3 )/GaN Photocatalysts.

J. Phys. Chem. Lett., 4: 21 (2013) 3719-3724

DOI: 10.1021/jz401884c

Catalysis; Catalysts; LEIS; Qtac; Multiple Techniques; Application Paper

 

The supported (Rh2−yCryO3)/GaN photocatalyst was examined as a model nitride photocatalyst system to assist in the development of fundamental structure−photoactivity relationships for UV activated water splitting. Surface characterization of the outermost surface layers by high-sensitivity low energy ion scattering (HS-LEIS) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) revealed that the GaN support consists of a GaOx outermost surface layer on a thin film of GaOxNy. HR-XPS demonstrates that the supported (Rh2−yCryO3) mixed oxide () 3 nanoparticles (NPs) consist of Cr3+ and Rh3+ cations that are surface enriched for (Rh2−yCryO3)/ y GaN. Raman and UV−vis spectroscopy show that the bulk molecular and electronic structures, respectively, of the GaN support are not perturbed by the deposition of the (Rh2−yCryO3) NPs. The function of the GaN bulk lattice is to generate photoexcited electrons/holes, with the electrons harnessed by the surface Rh3+ sites for evolution of H2 and the holes trapped at the Ga oxide/oxynitride surface sites for splitting of water and evolving O2.

 

Contact: ION-TOF, Thomas Grehl

________________________________

R.C. Monreal, D. Goebl, D. Primetzhofer, and P. Bauer

Effects of the atomic level shift in the Auger neutralization rates of noble metal surfaces

Nucl. Instr. Meth. B, 317:  (2013) 206

DOI: http://dx.doi.org/10.1016/j.nimb.2013.03.031

Charge exchange, Auger neutralization, LEIS, Noble metals

 

In this work we compare characteristics of Auger neutralization of Heþ ions at noble metal and free-electron metal surfaces. For noble metals, we find that the position of the energy level of He with respect to the Fermi level has a non-negligible influence on the values of the calculated Auger rates through the evaluation of the surface dielectric susceptibility. We conclude that even though our calculated rates are accurate, further theoretical effort is needed to obtain realistic values of the energy level of He in front of these surfaces.

 

Contact: Johannes Kepler Universität Linz, Peter Bauer

________________________________

Rafati, Ali; ter Veen, Rik; Castner, David G.

Low energy ion scattering: Determining overlayer thickness for functionalized gold nanoparticles.

Surface and interface analysis, 45: 11-12 (2013) 2013

DOI: 10.1002/sia.5315

Nanoparticles; LEIS; Qtac

 

With the widespread use of engineered nanoparticles for biomedical applications, detailed surface characterization is essential for ensuring reproducibility and the quality/suitability of the surface chemistry to the task at hand. One important surface property to be quantified is the overlayer thickness of self-assembled monolayer (SAM) functionalized nanoparticles, as this information provides insight into SAM ordering and assembly. We demonstrate the application of high sensitivity low energy ion scattering (HS-LEIS) as a new analytical method for the fast thickness characterization of SAM functionalized gold nanoparticles (AuNPs). HS-LEIS demonstrates that a complete SAM is formed on 16-mercaptohexadecanoic acid (C16COOH) functionalized 14 nm AuNPs. HS-LEIS also experimentally provides SAM thickness values that are in good agreement with previously reported results from simulated electron spectra for surface analysis (SESSA) analysis of X-ray photoelectron spectroscopy (XPS) data. These results indicate HS-LEIS is a valuable surface analytical method for the characterization of SAM functionalized nanomaterials.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Rik ter Veen, Michael Fartmann, Reinhard Kersting, and Birgit Hagenhoff

Combining dynamic and static depth profiling in low energy ion scattering

Journal of Vacuum Science and Technology A, 31:  (2013) 01A113

DOI: 10.1116/1.4764111

LEIS; Qtac

 

The advantages of combining dynamic and static depth profiling in low energy ion scattering are demonstrated for an Si/SiOx/W/Al2O3 ALD stack. Dynamic depth profiling can be used to calibrate static depth profiling. Energy losses of 152 and 215 eV/nm were found for 3 keV 4He+ and 5 keV 4He+ primary ions, respectively, for the experimental configuration used. This is in good agreement with the values used in the field. Static depth profiling can be used to recognize sputter artifacts in dynamic depth profiles.

 

Contact: Tascon, Rik ter Veen

________________________________

Shin, Hyun Ho; McIntosh, Steven

On the H2/D2 isotopic exchange rate of proton conducting barium cerates and zirconates.

J. Mater. Chem. A, 1: 26 (2013) 7639

DOI: 10.1039/c3ta10740j

Ceramics; Fuel Cells; LEIS; Qtac

 

H2/D2 pulse isotope exchange experiments were employed for the first time to gain insight into the hydrogen oxidation mechanism of proton conducting solid oxide fuel cell electrode materials. Phase pure perovskites, BaCeO3 (BC), BaCe0.9Y0.1O3?? (BCY), BaZrO3 (BZ) and BaZr0.9Y0.1O3?? (BZY) were synthesized. The experiment was performed in both dry and wet H2, isotopic exchange was clearly observed over all samples between 250 and 525 °C in dry H2, 425 and 725 °C in wet H2. The conversion of D2 reached above 88% at 375 °C in BC and BCY, 550 and 425 °C in BZ and BZY respectively; however, no significant difference in rate was observed between the materials. Surface composition analysis via High Sensitivity-Low Energy Ion Scattering (HS-LEIS) and X-ray photoelectron spectroscopy (XPS) revealed significant Ba enrichment on the outermost surface (71.1-87.1%, fractional surface coverage of Ba). It is suggested that this similar surface composition leads to similar catalytic activity. Significant rate enhancement was observed upon 1 wt% surface doping with active transition metal catalysts, Ni, Pt and Co. We suggest that hydrogen dissociation occurs primarily on the metallic component of H+-SOFC cermet anodes.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Wachs, Israel E.; Phivilay, Somphonh P.; Roberts, Charles A.

Reporting of Reactivity for Heterogeneous Photocatalysis.

ACS Catalysis, 3: 11 (2013) 2606-2611

DOI: 10.1021/cs4005979

LEIS; Qtac; Application Paper

 

The absence of standardization in both the measurement  and the reporting of heterogeneous photocatalysis  reactivity data has prevented quantitative comparisons between  different photocatalysts and advances in fundamental understanding  of the photocatalysis reaction, respectively. The call  for adoption of a standard photocatalysis measurement  procedure, to prevent masking of the photocatalysis reactivity  by saturation of light absorption or mass transfer effects, was  recently proposed to allow ranking of different photocatalysts  for their performance and comparison of reactivity reported  from different laboratories.1,2 Adoption of the standardized  measurement protocols by photocatalysis researchers is indeed  critical for advancing the heterogeneous photocatalysis field.  Standardized reactivity measurement, however, still does not  address fundamental aspects of the photocatalysis process (e.g.,  structure?activity relationships), which would require normalizing  the reactivity per number of surface photocatalytic active  sites as is practiced for heterogeneous catalysis.1

 

Contact: ION-TOF, Thomas Grehl

________________________________

Bruns, M.; Barth, C.; Brüner, P.; Engin, S.; Grehl, T.; Howell, C. et al.

Structure and chemical composition of mixed benzylguanine- and methoxy-terminated self-assembled monolayers for immobilization of biomolecules. ECASIA special issue paper.

Surface and Interface Analysis, 44: 8 (2012) 909-913

DOI: 10.1002/sia.4876

Self Assembled Monolayers; LEIS; Qtac; XPS; Application Paper

 

Covalent immobilization of biomolecules has become a subject of great interest in recent years because of the expected diversity of applications, for example, biosensors in diagnosis, lab-on-chip technology, and modern cell culture focused on cell adhesion, migration, and differentiation. Our approach is to produce self-assembled monolayers (SAMs) on gold surfaces based on mixtures of a benzylguanine-terminated thiol and a thiol, carrying ethylene glycol groups. The benzylguanine head group of such SAMs acts as a substrate for the SNAP-tag system allowing for covalent attachment of any protein of interest fused to this tag. For this purpose, it is essential to determine the orientation and chemical composition of these layers. In this study, we use the strength of combining complementary surface analytical methods to achieve a comprehensive characterization. The chemical composition and the covalent binding of the thiols were proved by X-ray photoelectron spectroscopy (XPS). The orientation of the SAMs together with thickness information was achieved by nondestructive depth profiles reconstructed from parallel angle-resolved XPS data and energy-resolved photoelectron emission spectroscopy (PES). High-sensitivity low-energy ion scattering and sum-frequency-generation spectroscopy corroborate the XPS/PES results.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Téllez, H.; Chater, R. J.; Fearn, S.; Symianakis, E.; Brongersma, H. H.; Kilner, J. A.

Determination of 16O and 18O sensitivity factors and charge-exchange processes in low-energy ion scattering.

Applied Physics Letters, 101: 15 (2012) 151602

DOI: 10.1063/1.4758699

Fuel Cells; LEIS; Qtac; Application Paper; Instrumental Paper

 

Quantitative analysis in low-energy ion scattering (LEIS) requires an understanding of the charge-exchange processes to estimate the elemental sensitivity factors. In this work, the neutralization of He+ scattered by 18O-exchanged silica at energies between 0.6 and 7 keV was studied. The process is dominated by Auger neutralization for Ei < 0.8 keV. An additional mechanism starts above the reionization threshold. This collision-induced neutralization becomes the dominant mechanism for Ei > 2 keV. The ion fractions P+ were determined for Si and O using the characteristic velocity method to quantify the surface density. The 18O/16O sensitivity ratio indicates an 18% higher sensitivity for the heavier O isotope.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Brumbach, Michael T.; Ohlhausen, James A.; Zavadil, Kevin R.; Snow, Clark S.; Woicik, Joseph C.

Activation of erbium films for hydrogen storage.

Journal of Applied Physics, 109: 11 (2011) 114911

DOI: 10.1063/1.3590335

LEIS; Qtac; Application Paper

 

Hydriding of metals can be routinely performed at high temperature in a rich hydrogen atmosphere. Prior to the hydrogen loading process, a thermal activation procedure is required to promote facile hydrogen sorption into the metal. Despite the wide spread utilization of this activation procedure, little is known about the chemical and electronic changes that occur during activation and how this thermal pretreatment leads to increased rates of hydrogen uptake. This study utilized variable kinetic energy X-ray photoelectron spectroscopy to interrogate the changes during in situ thermal annealing of erbium films, with results confirmed by time-of-flight secondary ion mass spectrometry and low energy ion scattering. Activation can be identified by a large increase in photoemission between the valence band edge and the Fermi level and appears to occur over a two stage process. The first stage involves desorption of contaminants and recrystallization of the oxide, initially impeding hydrogen loading. Further heating overcomes the first stage and leads to degradation of the passive surface oxide leading to a bulk film more accessible for hydrogen loading.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Grehl, T.; Niehuis, E.; Brongersma, H. H.

Surface Microanalysis by Low-Energy Ion Scattering.

Microscopy Today, 19: 2 (2011) 34-38

DOI: 10.1017/S1551929511000095

LEIS; Qtac; Commercial Paper; Review Paper

 

Low-energy ion scattering (LEIS) has gained new capabilities and now provides high-end instrumentation for real-world surface analytical applications [1]. Although the technique has been available for some decades, recent developments in instrumentation make the unique capabilities of LEIS accessible for everyday applications. Special ion energy analyzer designs allow LEIS to be used for non-destructive quantitative analysis of the elemental composition of the outermost atomic layer with high sensitivity and high mass resolution. At the same time, the composition of the first 10 nm of sub-surface material is also assessed. Applications are very broad, ranging from catalysts to various thin films to polymers.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Kilner, John A.; Skinner, Stephen J.; Brongersma, Hidde H.

The isotope exchange depth profiling (IEDP) technique using SIMS and LEIS.

Journal of Solid State Electrochemistry, 15: 5 (2011) 861-876

DOI: 10.1007/s10008-010-1289-0

Fuel Cells; LEIS; Qtac; TOF-SIMS; Application Paper; Review Paper

 

The determination of the mass transport kinetics of oxide materials for use in electrochemical systems such as fuel cells, sensors and oxygen separators is a significant challenge. Several techniques have been proposed to derive these data experimentally with only the oxygen isotope exchange depth profile technique coupled with secondary ion mass spectrometry (SIMS) providing a direct measure of these kinetic parameters. Whilst this allows kinetic information to be obtained, there is a lack of knowledge of the surface chemistry of these complex processes. The advent of low-energy ion scattering (LEIS) now offers the opportunity of correlating exchange kinetics with chemical processes at materials atomic surfaces, giving unprecedented levels of information on electrochemical systems with isotopic discrimination. Here, the challenges of these techniques, including sample preparation, are discussed and the advantages of the combined approach of SIMS and LEIS illustrated with reference to key literature

 

Contact: ION-TOF, Thomas Grehl

________________________________

Py, Matthieu; Barnes, Jean Paul; Grehl, Thomas; Brüner, Philipp; Gambacorti, Narciso; Hartmann, J. M.

Quantitative profiling of SiGe/Si superlattices with extended Full Spectrum ToF-SIMS and LEIS. Poster.

IBA 2011., :  (2011)

DOI:

Semiconductors; SiGe; LEIS; Qtac; TOF-SIMS; Application Paper

 

 

Contact: ION-TOF, Thomas Grehl

________________________________

Beekmans, H.; Breitenstein, Daniel; Brongersma, Hidde H.; de Ridder, Marco; Tromp, Th.J.

Significant improvement of the osseointegration of zirconia dental implants by HS-LEIS analysis.

Nuclear Instruments and Methods in Physics Research B., 268: 11 - 12 (2010) 2172 - 2176

DOI: 10.1016/j.nimb.2010.02.043

LEIS; Qtac; Application Paper

 

The use of sintered yttria stabilized zirconia dental implants is a recent development. After initial successes with these new implants a pattern of erratic results emerged. Reliable osseointegration would not always occur. High-sensitivity low energy ion scattering (HS-LEIS) is used to investigate both virgin and rejected implants. The surfaces of the implant are found to be covered with both an organic and inorganic contamination layer. Sterilization does not remove this contamination. Using LEIS as analytic tool a new cleaning process has been developed. Since this cleaning process is in use, the failure rate has dropped to a very low value.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Brongersma, Hidde H.; Grehl, Thomas; Schofield, Emma R.; Smith, Richard A.P.; ter Veen, Hendrik R.J.

Analysis of the Outer Surface of Platinum-Gold Catalysts by Low-Energy Ion Scattering.

Platinum Metals Review, 54: 2 (2010) 81-87

DOI: 10.1595/147106710x494358

LEIS; Catalysis; Catalysts; Qtac; Instrumental Paper

 

Low-energy ion scattering (LEIS) can be used to selectively analyse the atomic composition of the outer atomic layer of a catalyst, i.e., precisely the atoms that largely determine its activity and selectivity. It is shown how a new development in LEIS significantly improves its mass resolution. Using this advanced separation and quantification of signals from platinum and gold, the atomic composition of the outer surface of a realistic supported platinum-gold bimetallic system can be determined for the first time.

 

Contact: ION-TOF, Thomas Grehl

________________________________

Brongersma, Hidde H.; Grehl, Thomas; van Hal, Paul A.; Kuijpers, Niels C.W.; Mathijssen, Simon G.J.; Schofield, Emma R. et al.

High-sensitivity and high-resolution low-energy ion scattering.

Vacuum, 84: 8 (2010) 1005-1007

DOI: 10.1016/j.vacuum.2009.11.016

LEIS; Qtac; Review Paper

 

Low-Energy Ion Scattering (LEIS or ISS) is used to selectively analyze the atomic composition of the outer atomic layer of surfaces. In addition, the spectrum gives (non-destructively) the in-depth distribution. Using a double toroidal energy analyzer with parallel energy detection and time-of-flight filtering a high sensitivity and mass resolution of LEIS is achieved. This is demonstrated for a highly dispersed catalyst of Pt/Au on g-alumina. The improved depth resolution is illustrated for self-assembled monolayers of alkanethiols (12-20 carbon atoms) on gold. Even for these low Z carbon atoms a clear shift of 8 eV/carbon atom is observed (using 1.5 keV 4Heþ ion scattering). This opens many new possibilities for studies of ultra-thin diffusion barriers, high-k dielectrics and biosensors

 

Contact: ION-TOF, Thomas Grehl

________________________________

Fuchs, M.; Breitenstein, Daniel; Fartmann, Michael; Grehl, Thomas; Koester, R.; Ochs, R. et al.

Characterization of core/shell nanoparticle thin films for gas analytical applications.

Surface and Interface Analysis, 42: 6-7 (2010) 1131-1134

DOI: 10.1002/sia.3223

Nanoparticles; LEIS; Qtac; Application Paper

 

Gas analytical micro systems such as the Karlsruhe micro nose (KAMINA) can be improved toward higher sensitivity when using SnO2 nanoparticle thin films instead of well-established sputtered layers. For achieving long-term stability, such nanoparticles must be prevented from growing and agglomerating. A very promising approach is to coat SnO2 nanoparticles with an open-pored SiO2 shell, simply acting as a spacer, while preserving electrical contact between adjacent core particles. Such nanoparticulate thin films can easily be realized by the gas-phase Karlsruhemicrowave plasma process (KMPP). This provides an all-in-one approach to synthesize particles with diameters less than 10 nm, to coat them in situ with a protective ultrathin SiO2 shell in a downstream step and to finally deposit the core/shell particles solvent-free onto prefabricated micro devices. The present study focuses on the surface analytical characterization of 200 nm thin films consisting of SnO2 core/SiO2 shell nanoparticles with various shell designs. For this purpose, the SiO2 shell thickness was systematically increased while keeping the SnO2 core size constant. X-ray photoelectron spectroscopy (XPS) provides information concerning chemical binding states and shell thickness in a nondestructive manner. Angle-resolved XPS together with transmission electron microscopy (TEM) validate the achieved core/shell structure. In the case of the desired ultrathin SiO2 shells, low-energy ion scattering (LEIS) is solely the suitablemeans to prove that Sn and Si are the constituents of the outermostmonolayer of the spherical particles and it demonstrates the attainability of open-pored coatings.

 

Contact: ION-TOF, Thomas Grehl

________________________________

H. Beekmans, D. Breitenstein, H.H. Brongersma, M. de Ridder, Th.J. Tromp

Significant improvement of the osseointegration of zirconia dental implants by HS-LEIS analysis

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 268: 11-12 (2010) 2172-2176

DOI: 10.1016/j.nimb.2010.02.043

LEIS; Zirconia; Dental implant; Surface composition; Surface analysis; Cleaning

 

The use of sintered yttria stabilized zirconia dental implants is a recent development. After initial successes with these new implants a pattern of erratic results emerged. Reliable osseointegration would not always occur. High-sensitivity low energy ion scattering (HS-LEIS) is used to investigate both virgin and rejected implants. The surfaces of the implant are found to be covered with both an organic and inorganic contamination layer. Sterilization does not remove this contamination. Using LEIS as analytic tool a new cleaning process has been developed. Since this cleaning process is in use, the failure rate has dropped to a very low value.

 

Contact: Tascon, Rik ter Veen

________________________________

H. H. Brongersma, T. Grehl, E. R. Schofield, R. A. P. Smith and H. R. J. ter Veen,

Analysis of the Outer Surface of Platinum-Gold Catalysts by Low-Energy Ion Scattering. Improved resolution allows selective analysis of mixed metal systems

Platinum Metals Review, 54: 2 (2010) 81-87

DOI: 10.1595/147106710X494358

 

Low-energy ion scattering (LEIS) can be used to selectively analyse the atomic composition of the outer atomic layer of a catalyst, i.e., precisely the atoms that largely determine its activity and selectivity. It is shown how a new development in LEIS significantly improves its mass resolution. Using this advanced separation and quantification of signals from platinum and gold, the atomic composition of the outer surface of a realistic supported platinum-gold bimetallic system can be determined for the first time.

 

Contact: Tascon, Rik ter Veen

________________________________

H. H. Brongersma, T. Grehl, P. A. van Hal, N. C. W. Kuijpers, S. G. J. Mathijssen, E. R. Schofield, R. A. P. Smith and H. R. J. ter Veen,

High-sensitivity and high-resolution low-energy ion scattering

Vacuum, 84: 8 (2010) 1005-1007

DOI: 10.1016/j.vacuum.2009.11.016

LEIS, High sensitivity, Mass resolution, Depth resolution, Self-assembled monolayer

 

Quantitative Low-Energy Ion Scattering (LEIS or ISS) is used to selectively analyze the atomic composition of the outer atomic layer of surfaces. In addition, the spectrum gives (non-destructively) the in-depth distribution. Using a double toroidal energy analyzer with parallel energy detection and time-of-flight filtering a high sensitivity and mass resolution of LEIS is achieved. This is demonstrated for a highly dispersed catalyst of Pt/Au on [gamma]-alumina. The improved depth resolution is illustrated for self-assembled monolayers of alkanethiols (12-20 carbon atoms) on gold. Even for these low Z carbon atoms a clear shift of 8 eV/carbon atom is observed (using 1.5 keV 4He+ ion scattering). This opens many new possibilities for studies of ultra-thin diffusion barriers, high-k dielectrics and biosensors.

 

Contact: Tascon, Rik ter Veen

________________________________

V. I. T. A. d. Rooij-Lohmann, A. E. Yakshin, R. W. E. v. d. Kruijs, E. Zoethout, A. W. Kleyn, E. G. Keim, M. Gorgoi, F. Schäfers, H. H. Brongersma and F. Bijkerk,

Enhanced diffusion upon amorphous-to-nanocrystalline phase transition in Mo/B4C/Si layered systems

Journal of Applied Physics, 108:  (2010) 14314

DOI: 10.1063/1.3460107

 

The effect of an amorphous-to-nanocrystalline phase transition on the diffusion across an interface layer of subnanometer thickness has been investigated in real-time. The diffusion in the Mo/B4C/ Si thin film structure studied was found to instantaneously enhance by an order of magnitude upon the formation of nanocrystals inducing the atomic-scale onset of grain boundary diffusion.

 

Contact: Tascon, Rik ter Veen

________________________________

H. R. J. ter Veen, T. Kim, I. E. Wachs and H. H. Brongersma,

Applications of High Sensitivity-Low Energy Ion Scattering (HS-LEIS) in heterogeneous catalysis

Catalysis Today, 140: 3 (2009) 197-201

DOI: 10.1016/j.cattod.2008.10.012

High Sensitivity-Low Energy Ion Scattering (HS-LEIS), Heterogeneous catalysis, Surface analysis, MoO3/TiO2

 

High Sensitivity-Low Energy Ion Scattering (HS-LEIS) is a sensitive analysis technique for the outermost atomic layer of a sample. On a heterogeneous catalyst, this outermost atomic layer is the precise location where the catalytic processes take place. Based on the principles of classical mechanics, HS-LEIS determines the mass of surface atoms by measuring the energy from ions that are scattered from the surface. Examples with pure oxides, mixed oxides and supported metal oxide catalyst samples are presented to demonstrate the sensitivity, the ease of quantification, the availability of information about layers immediately beneath the surface (relevant for the dispersion of the active catalytic component on the surface of the catalyst) as well as the potential for High Throughput Experimentation (HTE) due to the short analysis times.

 

Contact: Tascon, Rik ter Veen

________________________________

R. Andrzejewski, V. Kuzmin, D. O. Boerma, D. Primetzhofer, S. N. Markin and P. Bauer,

Azimuthal scans in LEIS: Influence of the scattering potential

Nuclear Instruments and Methods in Physics Research B, 267: 4 (2009) 638-641

DOI: 10.1016/j.nimb.2008.11.021

 

 

Contact: Tascon, Rik ter Veen

________________________________

T. Tanabe, Y. Nagai, T. Hirabayashi, N. Takagi, K. Dohmae, N. Takahashi, S. i. Matsumoto, H. Shinjoh, J. N. Kondo, J. C. Schouten and H. H. Brongersma,

Low temperature CO pulse adsorption for the determination of Pt particle size in a Pt/cerium-based oxide catalyst

Applied Catalysis A: General, 370: 1-2 (2009) 108-113

DOI: 10.1016/j.apcata.2009.09.030

Pt particle size, Cerium-based oxide, CO adsorption, X-ray diffraction, Low energy ion scattering

 

Unexpectedly large amounts of CO adsorption have resulted from a pulse adsorption experiment at 323 K, giving about 300% Pt dispersion in a Pt/cerium-based oxide catalyst. An in situ diffuse reflectance infrared Fourier transform spectroscopic investigation on a Pt/cerium-based oxide during CO adsorption has revealed that carbonate species on the cerium oxide surface are responsible for the unrealistically large CO adsorption at 323 K, as a result of CO spillover. Lowering the temperature to 195 K considerably diminished the amount of CO adsorption. The size of the Pt particles in the Pt/cerium-based oxide catalyst was determined by CO pulse adsorption at 195 K and showed good agreement with the particle size determined by X-ray diffraction and low energy ion scattering. This indicates that CO pulse adsorption at 195 K is a useful technique to reliably estimate the Pt particle size in a Pt/cerium-based oxide catalyst.

 

Contact: Tascon, Rik ter Veen

________________________________

T. Wu, W. E. Kaden, W. A. Kunkel and S. L. Anderson,

Size-dependent oxidation of Pdn (n [less-than-or-equals, slant] 13) on alumina/NiAl(110): Correlation with Pd core level binding energies

Surface Science, 603: 17 (2009) 2764-2770

DOI: 10.1016/j.susc.2009.07.014

Low energy ion scattering (LEIS), X-ray photoelectron spectroscopy, Oxidation, Palladium, Alumina

 

Small Pd clusters Pdn (n = 1, 4, 7, 10, 13) deposited on alumina/NiAl(110) at room temperature were examined by X-ray photoelectron spectroscopy (XPS), as-deposited and after exposure to O2 at temperatures ranging from 100 to 500 K. After O2 exposure at 100 K, the Pd clusters showed XPS shifts indicative of oxidation. The exception was Pd4, which did not oxidize under any conditions. The inertness of Pd4/alumina/NiAl(110) appears to be correlated with a significantly higher-than-expected Pd 3d binding energy, which we attribute to a particularly stable valence shell. None of the clusters examined oxidized during O2 exposures at 300 K or above, but He+ scattering showed that oxygen was bound on the cluster surfaces. Upon heating, all the oxygen associated with these small clusters appeared to spill over and react with the alumina/NiAl(110) support.

 

Contact: Tascon, Rik ter Veen

________________________________

V. I. T. A. d. Rooij-Lohmann, A. W. Kleyn, F. Bijkerk, H. H. Brongersma and A. E. Yakshin,

Diffusion and interaction studied nondestructively and in real-time with depth-resolved low energy ion spectroscopy

Applied Physics Letters, 94:  (2009) 63107

DOI: 10.1063/1.3081034

Atomic, molecular and ion beam impact and interactions with surfaces. Self-diffusion and ionic conduction in solid nonmetals

 

An analysis procedure was developed that enables studying diffusion in ultrathin films by utilizing the depth-resolved information that is contained in the background of low energy ion scattering (LEIS) spectra. Using a high-sensitivity analyzer/detector combination allows for such a low ion dose that the ion-induced perturbation caused by this technique is negligible and not measurable with LEIS. The developed analysis procedure provides a unique opportunity to study diffusion processes in nanoscaled systems. It was applied to the Mo/Si system, a system that is relevant for extreme ultraviolet optics.

 

Contact: Tascon, Rik ter Veen

________________________________

Y. Yun, N. Pilet, U. D. Schwarz and E. I. Altman,

Comparison of the interaction of Pd with positively and negatively poled LiNbO3(0 0 0 1)

Surface Science, 603: 20 (2009) 3145-3154

DOI: 10.1016/j.susc.2009.08.030

Palladium, Metal-insulator interfaces, Carbon monoxide, Thermal desorption, X-ray photoelectron spectroscopy, Low energy ion scattering (LEIS)

 

To investigate the possibility of manipulating the surface chemical properties of finely dispersed metal films through ferroelectric polarization, the interaction of palladium with oppositely poled LiNbO3(0 0 0 1) substrates was characterized. Low energy ion scattering indicated that the Pd tended to form three-dimensional clusters on both positively and negatively poled substrates even at the lowest coverages. X-ray photoelectron spectroscopy (XPS) showed an upward shift in the binding energy of the Pd 3d core levels of 0.9 eV at the lowest Pd coverages, which slowly decayed toward the bulk value with increasing Pd coverage. These shifts were independent of the poling direction of the substrate and similar to those attributed to cluster size effects on inert supports. Thus, the spectroscopic data suggested that Pd does not interact strongly with LiNbO3 surfaces. The surface chemical properties of the Pd clusters were investigated using CO temperature programmed desorption. On both positively and negatively poled substrates, CO desorption from freshly deposited Pd showed a splitting of the broad 460 K desorption peak characteristic of bulk Pd into distinct peaks at 270 and 490 K as the Pd coverage was decreased below 1.0 ML; behavior that also resembles that seen on inert supports. It was found that a small fraction of the adsorbed CO may dissociate (<2%) for Pd on both positively and negatively poled substrates. The thermal response of the smaller Pd clusters on the LiNbO3 surfaces, however, was different from that of inert substrates. In a manner similar to Nb2O5, when CO desorption experiments were carried out a second time, the adsorption capacity decreased and the higher temperature desorption peak shifted from 490 K to below 450 K. This behavior was independent of the substrate poling direction. Thus, while there was evidence that LiNbO3 does not behave as a completely inert support, no significant differences between positively and negatively poled surfaces were observed. This lack of sensitivity of the surface properties of the Pd to the poling direction of the substrate is attributed to the three-dimensional Pd clusters being too thick for their surfaces to be influenced by the polarization of the underlying substrate.

 

Contact: Tascon, Rik ter Veen

________________________________

A. Celaya Sanfiz, T. W. Hansen, A. Sakthivel, A. Trunschke, R. Schlögl, A. Knoester, H. H. Brongersma, M. H. Looi and S. B. A. Hamid,

How important is the (001) plane of M1 for selective oxidation of propane to acrylic acid?

Journal of Catalysis, 258: 1 (2008) 35-43

DOI: 10.1016/j.jcat.2008.05.028

MoVTeNb oxide catalyst, M1, Propane oxidation, Propane ammoxidation, Low-energy ion scattering, LEIS

 

The role of the (001) crystallographic plane of the M1 phase of MoVTeNb mixed-oxide catalysts in selective oxidation of propane to acrylic acid was addressed by investigating a phase-pure M1 material preferentially exposing this surface. A model catalyst was prepared by complete silylation of M1, followed by breakage of the SiO2-covered needles. Using this approach, the reactivity of the M1 (001) surface was investigated by combining a microreactor study of propane oxidation with high-sensitivity low-energy ion scattering (HS-LEIS). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the shape and microstructure of the model system and verify the surface exposure of the model catalyst. The specific rate of formation of acrylic acid on the model catalyst was found to be similar to that on the phase-pure M1 reference material, indicating that the (001) plane of the M1 crystal structure did not have better catalytic properties compared with the lateral surface of M1 needles in propane oxidation.

 

Contact: Tascon, Rik ter Veen

________________________________

D. Primetzhofer, S. Markin, J. Juaristi, E. Taglauer and P. Bauer,

Crystal Effects in the Neutralization of He+ Ions in the Low Energy Ion Scattering Regime

Physical Review Letters, 100: 21 (2008) 213201

DOI: 10.1103/PhysRevLett.100.213201

 

 

Contact: Tascon, Rik ter Veen

________________________________

D. Primetzhofer, S. N. Markin, M. Draxler, R. Beikler, E. Taglauer and P. Bauer,

Strength of the interatomic potential derived from angular scans in LEIS

Surface Science, 602: 17 (2008) 2921-2926

DOI: 10.1016/j.susc.2008.07.030

 

 

Contact: Tascon, Rik ter Veen

________________________________

D. Primetzhofer, S. N. Markin, P. Zeppenfeld, P. Bauer, S. Prusa, M. Kolibal and T. Sikola,

Quantitative analysis of ultra thin layer growth by time-of-flight low energy ion scattering

APPLIED PHYSICS LETTERS, 92:  (2008) 11929

DOI: 10.1063/1.2822816

 

 

Contact: Tascon, Rik ter Veen

________________________________

K. Khalal-Kouache, B. Aissous, A. Mekhtiche and A. C. Chami,

Effect of energy loss in the simulation of slow ion scattering by a solid surface

Nuclear Instruments and Methods in Physics Research B, 266: 5 (2008) 714-718

DOI: 10.1016/j.nimb.2007.11.043

Simulation, Energy loss, Multiple scattering, Monte Carlo, Transport theory, [pacs] 68.49.Sf, [pacs] 34.50.Bw, [pacs] 07.05.Tp, Ion surface scattering

 

As previously shown [B. Arezki, Y. Boudouma, P. Benoit-Cattin, A.C. Chami, C. Benazeth, K. Khalal, M. Boudjema, J. Phys.: Condens. Mat. 10 (1998) 741, K. Khalal-Kouache, A.C. Chami, M. Boudjema, P. Benoit-Cattin, C. Benazeth, Y. Boudouma,...

 

Contact: Tascon, Rik ter Veen

________________________________

D. Primetzhofer, S. N. Markin, R. Kolarova, M. Draxler, R. Beikler, E. Taglauer and P. Bauer,

On the surface sensitivity of angular scans in LEIS

Nuclear Instruments and Methods in Physics Research B, 258: 1 (2007) 36-39

DOI: 10.1016/j.nimb.2006.12.176

 

 

Contact: Tascon, Rik ter Veen

________________________________

H. H. Brongersma, M. Draxler, M. de Ridder and P. Bauer,

Surface composition analysis by low-energy ion scattering

Surface Science Reports, 62: 3 (2007) 63-109

DOI: 10.1016/j.surfrep.2006.12.002

LEIS, ISS, Quantitative surface composition analysis

 

Low-energy ion scattering (LEIS) is an analytical tool that provides information on the atomic composition of the outer surface, when noble gas ions are used as projectiles. In fact, quantitative composition analysis is currently done on a huge variety of materials, including catalysts and organic materials. The information on the surface composition is contained in the signal of backscattered ions (typically 1-3 keV He+,Ne+). In order to translate the LEIS signal to an elemental surface concentration all factors determining the LEIS signal must be known. These are in particular the scattering cross section and the ion fraction of the backscattered particles. The scattering cross section, which is due to the screened electrostatic potential between target atom and projectile, is well-known for the prevailing conditions of LEIS. It is an intriguing fact that, despite the large quantity of successful applications, the charge exchange processes in LEIS are not yet fully understood. It is e.g. not known why in LEIS for a given atomic species on the surface the signal usually does not depend on which other species are present (absence of matrix effects). Significant progress has recently been made in the understanding of the underlying charge exchange processes. Therefore, the aim of this review is twofold: on the one hand, to summarize the present understanding of the factors that determine the ion fraction of the scattered projectiles in LEIS, i.e. charge exchange processes. On the other hand, to summarize how quantitative surface composition analysis can be accomplished. In addition, we critically review publications that deal with surface composition analysis by LEIS, and analyze in which cases and by what means this was achieved and where and why it was successful or failed. After reading this review the reader will be able to deal with the pitfalls encountered in LEIS and to choose preferred experimental conditions for quantitative surface composition analysis.

 

Contact: Tascon, Rik ter Veen

________________________________

S. P. Chenakin, R. Kolarova, S. N. Markin, D. Primetzhofer and P. Bauer,

Influence of screening and electronic stopping on LEIS spectra

Nuclear Instruments and Methods in Physics Research B, 258: 1 (2007) 32-35

DOI: 10.1016/j.nimb.2006.12.173

 

 

Contact: Tascon, Rik ter Veen

________________________________

E. van der Wal, S. J. Oldenburg, T. Heij, A. W. Denier van der Gon, H. H. Brongersma, J. G. C. Wolke, J. A. Jansen and A. M. Vredenberg,

Adsorption and desorption of Ca and PO"4 species from SBFs on RF-sputtered calcium phosphate thin films

Applied Surface Science, 252: 10 (2006) 3843-3854

DOI: 10.1016/j.apsusc.2005.06.006

 

 

Contact: Tascon, Rik ter Veen

________________________________

V. V. Guliants, R. Bhandari, A. R. Hughett, S. Bhatt, B. D. Schuler, H. H. Brongersma, A. Knoester, A. M. Gaffney and S. Han,

Probe molecule chemisorption-low energy ion scattering study of surface active sites present in the orthorhombic Mo-V-(Te-Nb)-O catalysts for propane (amm)oxidation.

Journal of Physical Chemistry B, 110: 12 (2006) 6129-6140

DOI: 10.1021/jp056720f

 

 

Contact: Tascon, Rik ter Veen

________________________________

A. Delabie, R. L. Puurunen, B. Brijs, M. Caymax, T. Conard, B. Onsia, O. Richard, W. Vandervorst, C. Zhao, M. M. Heyns, M. Meuris, M. M. Viitanen, H. H. Brongersma, M. d. Ridder, L. V. Goncharova, E. Garfunkel, T. Gustafsson and W. Tsai,

Atomic layer deposition of hafnium oxide on germanium substrates

Journal of Applied Physics, 97:  (2005) 64104

DOI: 10.1063/1.1856221

 

 

Contact: Tascon, Rik ter Veen

________________________________

F. J. J. Janssen, A. W. Denier van der Gon, L. J. van IJzendoorn, R. Thoelen, M. J. A. de Voigt and H. H. Brongersma,

The influence of surface treatments on cathode formation and stability in polymer light emitting diodes

Applied Surface Science, 241: 3-4 (2005) 335-351

DOI: 10.1016/j.apsusc.2004.07.037

Conjugated polymers, Light emitting diodes, Surface treatment, Stability, Low energy ion scattering

 

We studied the stability of metal/polymer interfaces by measuring the diffusion of calcium into a polymer (OC1C10 PPV) layer during and after deposition of the metal using low energy ion scattering (LEIS) and X-ray photoelectron spectroscopy (XPS). During deposition the calcium diffusion depth in the PPV was found to be comparable for untreated samples and samples prepared in oxygen ambient (10-7 mbar). In both cases diffusion depths up to ~7 nm were observed. For PPV layers treated with atomic oxygen, the diffusion depth during deposition was slightly smaller. After deposition, it was observed that calcium diffusion in OC1C10 PPV continues for several hours. When oxygen was present during calcium deposition or during the spin coating of the PPV, the diffusion coefficient for calcium in PPV was decreased considerably. In these cases accumulation of oxygen (adsorbed in the PPV during deposition or spin coating) at the calcium/PPV interface continued for several hours after deposition. Treatment of the PPV with atomic oxygen before calcium deposition resulted in a strong decrease of the calcium diffusion coefficient after deposition. From XPS measurements it was observed that calcium interacts with the chemically bonded oxygen in the PPV and also with the oxygen absorbed in the PPV layer. It can be concluded that oxygen, either chemically bonded to the PPV chain or adsorbed in the film, reduces the calcium diffusion coefficient. The initial performance of PLEDs with atomic oxygen treated PPV layers and PLEDs with calcium deposited in oxygen ambient was worse than the performance of untreated devices, but the stability in the life-test was better.

 

Contact: Tascon, Rik ter Veen

________________________________

J. Zhu, J. G. van Ommen, A. Knoester and L. Lefferts,

Effect of surface composition of yttrium-stabilized zirconia on partial oxidation of methane to synthesis gas

Journal of Catalysis, 230: 2 (2005) 291-300

DOI: 10.1016/j.jcat.2004.09.025

 

 

Contact: Tascon, Rik ter Veen

________________________________

M. Draxler, J. E. Valdes, R. Beikler and P. Bauer,

On the extraction of neutralisation information from low energy ion scattering spectra

Nuclear Instruments and Methods in Physics Research B, 230: 1 (2005) 290-297

DOI: 10.1016/j.nimb.2004.12.057

 

 

Contact: Tascon, Rik ter Veen

________________________________

M. Draxler, P. Zeppenfeld, R. Beikler, E. Taglauer and P. Bauer,

Ion and neutral scattering spectra in LEIS

Nuclear Instruments and Methods in Physics Research B, 232: 1 (2005) 266-271

DOI: 10.1016/j.nimb.2005.03.056

 

 

Contact: Tascon, Rik ter Veen

________________________________

V. V. Guliants, R. Bhandari, B. Swaminathan, V. K. Vasudevan, H. H. Brongersma, A. Knoester, A. M. Gaffney and S. Han,

Roles of surface Te, Nb, and Sb oxides in propane oxidation to acrylic acid over bulk orthorhombic Mo-V-O phase.

Journal of Physical Chemistry B, 109: 50 (2005) 24046-24055

DOI: 10.1021/jp054641y

 

 

Contact: Tascon, Rik ter Veen

________________________________

V. V. Guliants, R. Bhandari, H. H. Brongersma, A. Knoester, A. M. Gaffney and S. Han,

A study of the surface region of the Mo-V-Te-O catalysts for propane oxidation to acrylic acid.

Journal of Physical Chemistry B, 109: 20 (2005) 10234-10242

DOI: 10.1021/jp044120v

 

 

Contact: Tascon, Rik ter Veen

________________________________

R. D. v. d. Grampel, W. Ming, A. Gildenpfennig, J. Laven, H. H. Brongersma, G. d. With and R. v. d. Linde,

Quantification of Fluorine Density in the Outermost Atomic Layer

Langmuir, 20:  (2004) 145-149

DOI: 10.1021/la0353071

 

The outermost atomic layer of perfluorinated thiol monolayers on gold and poly(tetrafluoroethylene) (PTFE) is analyzed by low-energy ion scattering. Absolute quantification of fluorine density in this layer was achieved after calibrating the fluorine signal with a freshly cleaved LiF(100) single crystal. The fluorine density of monolayers of a C8F17-thiol on gold was 1.48   1015 F atoms/cm2, whereas for PTFE a value of 1.24   1015 F atoms/cm2 was observed. This difference was explained by the different tilt angles of the thiol on gold and PTFE chains with respect to the surface normal. Both a configurational and a molecular interpretation on the perfluorinated thiol monolayer on gold are given.

 

Contact: Tascon, Rik ter Veen

________________________________

R. D. van de Grampel, W. Ming, A. Gildenpfennig, W. J. H. van Gennip, J. Laven, J. W. Niemantsverdriet, H. H. Brongersma, G. de With and R. van der Linde,

The outermost atomic layer of thin films of fluorinated polymethacrylates.

Langmuir, 20: 15 (2004) 6344-6351

DOI: 10.1021/la049519p

 

 

Contact: Tascon, Rik ter Veen

________________________________

R. L. Puurunen and W. Vandervorst,

Island growth as a growth mode in atomic layer deposition: A phenomenological model

JOURNAL OF APPLIED PHYSICS, 96:  (2004) 7686-7695

DOI: 10.1063/1.1810193

 

 

Contact: Tascon, Rik ter Veen

________________________________

R. L. Puurunen, W. Vandervorst, W. F. A. Besling, O. Richard, H. Bender, T. Conard, C. Zhao, A. Delabie, M. Caymax, S. D. Gendt, M. Heyns, M. M. Viitanen, M. d. Ridder, H. H. Brongersma, Y. Tamminga, T. Dao, T. d. Win, M. Verheijen, M. Kaiser and M. Tuomi

Island growth in the atomic layer deposition of zirconium oxide and aluminum oxide on hydrogen-terminated silicon: Growth mode ...

JOURNAL OF APPLIED PHYSICS, 96:  (2004) 4878-4889

DOI: 10.1063/1.1787624

 

 

Contact: Tascon, Rik ter Veen

________________________________

S. Y. Grachev, J. M. Gallego, D. Ecija, D. O. Boerma, R. Gonzalez-Arrabal and R. Miranda,

A combined LEIS/STM study of two types of surface reconstruction of magnetic Fe"4N layers

Nuclear Instruments and Methods in Physics Research B, 219:  (2004) 593-598

DOI: 10.1016/j.nimb.2004.01.126

 

 

Contact: Tascon, Rik ter Veen

________________________________

W. P. A. Jansen, A. Knoester, A. J. H. Maas, P. Schmit, A. Kytökivi, A. W. Denier v.d. Gon and H. H. Brongersma,

Influence of compaction and surface roughness on low-energy ion scattering signals

Surface and Interface Analysis, 36:  (2004) 1469–1478

DOI: 10.1002/sia.1921

surface roughness; neutralization; LEIS; ISS; compaction

 

Investigation of the surface composition of powders often requires compaction. To study the effect of compaction on surface analysis, samples have been compacted at various pressures ranging from 0 Pa (i.e. no compaction) up to 2000 MPa (2× 104 kg cm-2) Low-energy ion scattering (LEIS) was used to determine the composition of the outermost atomic surface layer. Using scanning electron microscopy, changes in the morphology due to compaction have been detected in the SiO2 test samples. The LEIS yield of a compacted silica powder is found to be independent of the applied pressure during compaction between 2MPa and 2000 MPa (2×104 kg cm-2). Analysis of a submonolayer of Ta2O5 on a silica support shows that the composition of the outermost atomic layer is not changed after compaction up to a pressure of at least 300 MPa. When compaction is applied, the absolute LEIS yield appears to be independent of the specific surface area of silica supports in the range 50–380 m2 g-1. A minor difference in LEIS signals is observed between compacted silica supports and flat quartz samples. In order to determine the surface roughness factor independently, and to study the material dependence of the surface roughness factor, angle-dependent LEIS measurements have been carried out on oxidized silicon, gallium and gold surfaces. The results on the oxidized silicon confirm the small influence of surface roughness for silica particles, whereas measurements on themore closely packed metallic gallium and gold surfaces indicate a significant surface roughness effect.

 

Contact: Tascon, Rik ter Veen

________________________________

B. Moest, S. Helfensteyn, P. Deurinck, M. Nelis, A. W. Denier van der Gon, H. H. Brongersma, C. Creemers and B. E. Nieuwenhuys,

The surface and step edge composition of clean and oxygen covered Pt50Rh50(5 1 1)

Surface Science, 536: 1-3 (2003) 177-190

DOI: 10.1016/S0039-6028(03)00597-1

Alloys, Vicinal single crystal surfaces, Surface segregation, Platinum, Rhodium, Ion scattering spectroscopy, Low energy ion scattering (LEIS), Ion-solid interactions

 

Low energy ion scattering has been used to perform site-specific composition measurements on Pt50Rh50(5 1 1) between room temperature and 1000 °C. The results show that the clean surface is strongly enriched in platinum. At all temperatures the Pt enrichment of the step edges is significantly larger than the Pt enrichment of the terraces, which can be attributed to the lower coordination of the step-edge atoms. A simple broken bond model is adequate to calculate the composition of the surface and the step edges at high temperatures. Between 650 and 800 °C a large decrease in Pt surface concentration occurs with increasing temperature. Two possible explanations are discussed here. The first is a bulk phase demixing at temperatures below 760 °C, which would lead to enhanced segregation due to the local increase of the Pt concentration in the sub-surface region. The second possible explanation is a surface phase transition from a missing row reconstruction below 650 °C to an unreconstructed surface above 800 °C. Here the enhanced segregation at lower temperatures is due to the decreased orientation of the surface atoms in the reconstructed phase. The influence of oxygen on the segregation is studied by measuring the surface and step-edge compositions after the adsorption and subsequent removal of oxygen. Following this preparation, the step-edge and surface Pt concentrations are equal to each other within the experimental accuracy. The results show weak Rh segregation on the oxygen treated surface, in contrast to the strong Pt segregation found on the clean surface.

 

Contact: Tascon, Rik ter Veen

________________________________

H. H. Brongersma, M. de Ridder, A. Gildenpfennig and M. M. Viitanen,

Insight in the outside: materials science at the atomic level using LEIS

Journal of the European Ceramic Society, 23: 15 (2003) 2761-2767

DOI: 10.1016/S0955-2219(03)00287-5

Films, Fuel Cells, Perovskites, Self-assembly, Surfaces

 

Modern low energy ion scattering (LEIS) can provide new information on the atomic composition of both outermost surface and sub-surface layers. The wide scope of new possibilities is illustrated with results on ceramics, polymers and ultra-thin layers. Most of the results presented are difficult or even impossible to obtain otherwise. The combination of LEIS and isotopic oxygen exchange reactions was used to investigate the surface of yttria stabilised zirconia (YSZ) that is used in the solid oxide fuel cell. It is found that under working conditions the surface is covered by a monolayer of contamination, followed by an yttria segregated layer. The quantification of LEIS is demonstrated for fluorinated self-assembled monolayers, while also the conformation of the endgroups is determined. The use of LEIS to follow the growth of ultra-thin layers is discussed for a TiN barrier layer on silicon.

 

Contact: Tascon, Rik ter Veen

________________________________

M. de Ridder, A. G. J. Vervoort, R. G. van Welzenis and H. H. Brongersma,

The limiting factor for oxygen exchange at the surface of fuel cell electrolytes

Solid State Ionics, 156: 3-4 (2003) 255-262

DOI: 10.1016/S0167-2738(02)00754-3

Surface composition, Impurities, Oxygen exchange, Yttria stabilised zirconia (YSZ), Low energy ion scattering (LEIS)

 

The outermost surface layer of the yttria stabilised zirconia (YSZ) electrolyte in the solid oxide fuel cell plays an important role in the performance of the cell. By combining 16O/18O exchange experiments with quantitative surface analysis by low energy ion scattering spectroscopy (LEIS), the relation between the composition of the outermost atomic layer and the oxygen kinetics at the surface of the electrolyte can be studied. The results suggest a linear relation between an increasing amount of impurity oxides present at the surface and a decreasing oxygen exchange. Ceramics invariably contain glassy impurities, which segregate to the grain boundaries during sintering. Our results, however, show that the accumulation is restricted to the outermost atomic layer and proceeds until complete coverage is obtained. This observation underlines the importance of the used surface analysis technique. The strong accumulation of the impurities at the surface is observed even in the purest YSZ materials available. A decrease of the total bulk impurity concentration by a factor of 10-100 is necessary to ensure that the YSZ surface cannot be covered completely by impurities. The amount of exchanged oxygen at the outermost surface layer reduces from 50% at a clean yttria stabilised zirconia surface to zero at a surface completely covered by impurity oxides. Although the oxygen exchange experiments pertain to a temperature of 500 °C it is believed that the impurity oxides also have a strong influence at higher temperatures.

 

Contact: Tascon, Rik ter Veen

________________________________

M. de Ridder, R. G. van Welzenis, H. H. Brongersma and U. Kreissig,

Oxygen exchange and diffusion in the near surface of pure and modified yttria-stabilised zirconia

Solid State Ionics, 158: 1 (2003) 67-77

DOI: 10.1016/S0167-2738(02)00759-2

 

 

Contact: Tascon, Rik ter Veen

________________________________

M. Draxler, R. Beikler, E. Taglauer, K. Schmid, R. Gruber, S. N. Ermolov and P. Bauer,

Explanation of the surface peak in charge integrated LEIS spectra

Nuclear Instruments and Methods in Physics Research B, 203:  (2003) 218-224

DOI: 10.1016/S0168-583X(02)02220-6

 

 

Contact: Tascon, Rik ter Veen

________________________________

A. G. J. Vervoort, P. J. Scanlon, M. de Ridder, H. H. Brongersma and R. G. van Welzenis,

Surface modification of a fuel cell material by ion implantation

Nuclear Instruments and Methods in Physics Research B, 190: 1-4 (2002) 813-816

DOI: 10.1016/S0168-583X(01)01308-8

Yttria stabilized zirconia, Low-energy ion scattering, Solid oxide fuel cell, Implantation, Segregation

 

 

Contact: Tascon, Rik ter Veen

________________________________

F. J. J. Janssen, L. J. van IJzendoorn, H. F. M. Schoo, J. M. Sturm, G. G. Andersson, A. W. D. van der Gon, H. H. Brongersma and M. J. A. de Voigt,

Degradation effects in poly para-phenylene vinylene derivatives due to controlled oxygen exposure

Synthetic Metals, 131: 1-3 (2002) 167-174

DOI: 10.1016/S0379-6779(02)00196-0

Conducting polymers, Light emitting diodes, Oxygen, Elastic recoil detection analysis, Polymer structure, Electrical characterisation

 

The influence of oxygen exposure on three chemically different poly para-phenylene vinylene (PPV) derivatives used in polymeric light emitting devices (PLEDs) has been investigated. During device preparation, PPV layers have been exposed to oxygen either in the dark or during the irradiation with visible light, before the cathode was applied. Device efficiency was studied by electrical and optical characterisation and correlated to oxygen depth profiles measured with Elastic Recoil Detection Analysis (ERDA). Treatment with oxygen during light exposure leads to a decrease in current, light output and efficiency. It was found that two different PPV derivatives show the same current and light output reduction with different oxygen uptake. This behaviour is explained in terms of a different chemical structure and the number of structural defects (tolane-bisbenzyl moieties (TBBs)) incorporated. For two PPV derivatives treated with oxygen in the dark a reduction in current and light output was found, while the efficiency was unchanged. Another PPV derivative, however, shows a shift in the on-set voltage of the light output accompanied by an increased oxygen level at the PPV/Ca interface. It is concluded that after exposure in the dark, oxygen is incorporated in the PPV by Van der Waals interaction. During evaporation of the cathodes, oxygen will diffuse to the cathode and will be gettered by the calcium, which results in the formation of an electron injection barrier.

 

Contact: Tascon, Rik ter Veen

________________________________

G. G. Andersson, W. J. H. van Gennip, J. W. Niemantsverdriet and H. H. Brongersma,

Calcium induced oxidation of PPV studied with X-ray photoelectron spectroscopy and secondary ion mass spectrometry

Chemical Physics, 278: 2-3 (2002) 159-167

DOI: 10.1016/S0301-0104(02)00383-X

Polymer light emitting diodes, Degradation mechanism, Polymer-metal interfaces, X-ray photoelectron spectroscopy (XPS), Secondary ion mass spectrometry (SIMS), Carbide formation

 

 

Contact: Tascon, Rik ter Veen

________________________________

H. H. Brongersma, A. Gildenpfennig, A. W. Denier van der Gon, R. D. van de Grampel, W. P. A. Jansen, A. Knoester, J. Laven and M. M. Viitanen,

Insight in the outside: New applications of low-energy ion scattering

Nuclear Instruments and Methods in Physics Research B, 190: 1 (2002) 11-18

DOI: 10.1016/S0168-583X(01)01314-3

 

 

Contact: Tascon, Rik ter Veen

________________________________

M. de Ridder, R. G. van Welzenis, H. H. Brongersma, S. Wulff, W.-F. Chu and W. Weppner,

Discovery of the rate limiting step in solid oxide fuel cells by LEIS

Nuclear Instruments and Methods in Physics Research B, 190: 1 (2002) 732-735

DOI: 10.1016/S0168-583X(01)01268-X

 

 

Contact: Tascon, Rik ter Veen

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M. M. Viitanen, R. G. v. Welzenis, H. H. Brongersma and F. P. F. van Berkel,

Silica poisoning of oxygen membranes

Solid State Ionics, 150: 3-4 (2002) 223-228

DOI: 10.1016/S0167-2738(02)00455-1

LEIS, ISS, Ion scattering, Oxygen membranes, Perovskite, Poisoning

 

Perovskite oxide membranes (La0.6Sr0.4Co0.2Fe0.8O3) are used for the separation of oxygen from air. In oxygen permeation experiments these membranes showed a peculiar behavior. Besides poor performance, a characteristic coloring also appeared on the surface of the membranes. In order to understand what was happening to the surface of the membranes, they were analysed with Low-Energy Ion Spectroscopy (LEIS) and X-ray Photoelectron Spectroscopy (XPS). The analyses showed that the surface of the LSCF membrane was covered with a SiO2 layer, which obviously reduced the performance and caused the coloring. It was established that the source of the silicon was siloxane containing grease that was used in the manual valves of the setup. In a new improved permeation setup, where grease-free valves were used, the LSCF membranes showed remarkably better performance. The LEIS measurements showed also that the permeation experiment of 300 h did not affect the surface composition of the membranes. The contamination-free LSCF membranes only showed the presence of La, Sr and O in the outermost atomic layer. The observed absence of Co and Fe suggests that further improvement of the membrane performance is possible.

 

Contact: Tascon, Rik ter Veen

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S. N. Ermolov, W. P. A. Jansen, S. N. Markin, V. G. Glebovsky and H. H. Brongersma,

The surfaces of Mo bicrystals studied by low-energy ion scattering

Surface Science, 512: 3 (2002) 221-228

DOI: 10.1016/S0039-6028(02)01663-1

Low energy ion scattering (LEIS), Molybdenum, Single crystal surfaces, Surface structure, morphology, roughness, and topography, Surface segregation

 

 

Contact: Tascon, Rik ter Veen

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W. P. A. Jansen, J. Beckers, J. C. v. d. Heuvel, A. W. Denier v. d. Gon, A. Bliek and H. H. Brongersma,

Dynamic Behavior of the Surface Structure of Cu/ZnO/SiO2 Catalysts

Journal of Catalysis, 210: 1 (2002) 229-236

DOI: 10.1006/jcat.2002.3679

 

In order to grasp the dynamic behavior of the surface composition of Cu/ZnO-based catalysts, the surface atomic densities of 63Cu and 68ZnO were determined separately with static LEIS on 63Cu/68ZnO/SiO2 catalysts. Our data show that the methanol synthesis activity and surface composition of 63Cu/68ZnO/SiO2 depend strongly on the reduction temperature between 473 and 673 K. The catalyst surface is strongly enriched in ZnO under methanol synthesis conditions. The oxidation state of the Cu species in the outermost atomic layer of the Cu/ZnO/SiO2 surface has been determined by performing LEIS in combination with adsorptive decomposition of N2O. The observed oxidation behavior of the Cu species differs clearly from pure metallic Cu. This oxidation behavior and the methanol synthesis activity of the reduced catalyst surface are explained in terms of the formation of Cu(I)/ZnO with oxygen vacancies and are shown to be clearly affected by the reducing agent (being 5% CO/5% CO2/90% H2 or pure H2).

 

Contact: Tascon, Rik ter Veen

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