Scanning Electron Probe Microanalysis

The combination of electron microprobe X-ray emission spectrometry with the scanning techniques first developed for the scanning electron microscope permits using the scanning electron probe as a microscope sensitive to elemental composition. This technique is particularly useful in the many applications in which spatial distribution of one or more elements in a specimen is more important than local composition. Although oscilloscope representation of probe scanning is usually obtained by the simple technique of producing a dot of light for each arriving photon, more sophisticated scanning techniques such as expanded contrast registration and concentration mapping can provide more quantitative information. Signals other than X-rays, such as target current, electron backscatter, or cathodoluminescence may be used for image formation. Electron beam scanning can be also performed in a discontinuous fashion, so that the electron beam irradiates in succession a number of spots arranged in a square rectangular pattern, and the number of photons registered in each position is retained in the memory of a multichannel analyzer. The application of these diverse scanning techniques is illustrated.