SEM/EDX

Scanning Electron Microscopy coupled with Energy Dispersive X-ray (SEM/EDX) Spectroscopy

Technique:
SEM Image Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX) is the best known and most widely-used of the surface analytical techniques. High resolution images of surface topography, with excellent depth of field, are produced using a highly-focused, scanning (primary) electron beam. The primary electrons enter a surface with an energy of 0.5 – 30 kV and generate many low energy secondary electrons. The intensity of these secondary electrons is largely governed by the surface topography of the sample. An image of the sample surface can thus be constructed by measuring secondary electron intensity as a function of the position of the scanning primary electron beam. High spatial resolution is possible because the primary electron beam can be focused to a very small spot (<10 nm). High sensitivity to topographic features on the outermost surface (< 5 nm) is achieved when using a primary electron beam with an energy of < 1 kV.

SEM NanotubesIn addition to low energy secondary electrons, backscattered electrons and X-rays are generated by primary electron bombardment. The intensity of backscattered electrons can be correlated to the atomic number of the element within the sampling volume. Hence, some qualitative elemental information can be obtained. The analysis of characteristic X-rays (EDX or EDS analysis) emitted from the sample gives more quantitative elemental information. Such X-ray analysis can be confined to analytical volumes as small as 1 cubic micron.

SEM, accompanied by X-ray analysis, is considered a relatively rapid, inexpensive, and basically non-destructive approach to surface analysis. It is often used to survey surface analytical problems before proceeding to techniques that are more surface-sensitive and specialized.

Instrument:
Hitachi S-4500 field emission SEM with a Quartz XOne EDX system

System Capabilities:

  • < 2nm spatial resolution at higher electron beam voltages (>15 kV)
  • Useful images at 100 K X magnification, or greater, can be obtained
  • Superb low voltage capability with < 5nm resolution available at 1 kV beam voltage
  • The low voltage capability means that many samples that normally require coating to reduce charging problems can be examined without coating
  • Elemental analysis from carbon to uranium
  • Semi-quantitative analysis with detection limits of ~ 0.5 weight % for most elements
  • EDX elemental mapping
  • The Quartz XOne system uses full spectral imaging, which allows for live and post-collection data analysis
  • Backscatter electron imaging
  • A maximum sample size of 50 mm diameter (~ 20 mm thick) can be accommodated.

Instrument:
LEO 440 SEM equipped with a Gresham light element detector and a Quartz XOne EDX system

System Capabilities:

  • Elemental analysis from carbon to uranium
  • Semi-quantitative analysis with detection limits of ~ 0.5 weight % for most elements
  • EDX elemental mapping
  • The Quartz XOne system uses full spectral imaging, which allows for live and post- collection data analysis
  • Samples up to 250 x 250 x 70 mm in size can be examined
  • Backscatter electron imaging

Selected Applications in Industry:

  • Imaging of a corroded copper surface
  • EDX analysis and mapping of dust from Beijing
  • Microstructure of a sputter-deposited silver film
  • Composition of a metallic brake pad
  • Pinhole in paint caused by cracks in the steel substrate