Photoelectron Spectroscopy

X-ray Photoelectron Spectroscopy (XPS / ESCA) is a method for the qualitative and quantitative analysis of elements near the surface of a solid. The sample is irradiated with monochromatic X-rays (Al Kα) which leads to emission of electrons by the atom that is excited by the photon (photoelectric effect). Only photoelectrons in the outer 5-10 nm can leave the sample without losing energy. A hemispherical energy analyser is used to register the kinetic energy of these electrons which is then recalculated in element specific binding energies. With XPS all elements (except for H and He) can be identified and quantified. Depending on the chemical surrounding of an element the binding energy can shift. This gives information about binding or oxidation states. The detection limits depend on the element and are typically between 0.1 and 1 atom-%.

XPS can be used to determine the element composition on very small spots (spot-Ø ≥ 10 µm) but also on areas with a size of a few mm². Point analysis along a line across the surface (linescan), 2D-element distributions (maps) or angle resolved analyses (ARXPS) for the characterisation of thin layers (< 10 nm) are common applications. It is also possible to determine the composition as a function of depth (depth profiling) by combining the XPS analysis with sputtering. The method can be used for a variety of vacuum compatible samples (e.g. metals, glasses, wafers, polymers, foils, ceramics, pigments, catalysts, etc.). 

A short description of this techniques is also available as pdf-file:

Synonyms / Related Techniques

  • X-ray Photoelectron Spectroscopy (XPS)
  • Electron Spectroscopy for Chemical Analysis (ESCA)