Scanning Electron Microscopy & Energy Dispersive X-Ray Analysis

In Scanning Electron Microscopy (SEM) a sample surface is scanned with a finely focussed electron beam. The electron bombardment leads to the emission of secondary electrons, backscattering of high energy primary electrons and creation of element specific X-rays.

The low energy secondary electrons originate from the top nanometers of the sample. The resulting images render the surface topography with a resolution in the nm range. The intensity of the scattered primary electrons, on the other hand, is determined by the average atomic number of the sample material. The corresponding images clarify the distribution of different materials (material contrast images). In this mode, the information depth is in the range of 1 µm. In addition, the element specific X-ray radiation is used for chemical characterisation of the surface near volume. With the aid of proper detectors, either the energy or the wave length of the X-rays is determined. The measured intensities yield quantitative information on the element composition and distribution. The depth from where the X-rays originate depends on the material and the used primary electron energy. For typical primary energies of 10 to 20 keV it is in the µm range.

Samples for SEM/EDX need to be vacuum compatible. Modern instruments can already be used at pressures around approx. 1 mbar (Environmental SEM).

Synonyms / Related Techniques

  • Environmental Scanning Electron Microscopy (ESEM)
  • Energy Dispersive X-ray Spectroscopy (EDX, EDRS, EDS)
  • Wavelength Dispersive X-ray Spectroscopy (WDX)
  • Electron Probe Micro Analysis (EPMA)

Case Studies