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Why is Auger electron spectroscopy useful for mapping surface composition?

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Moon rock crystals — surface analysis A scanning-electron-microscope photograph of pyroxene and plagioclase crystals (the long and the short crystals, respectively) that grew in a cavity in a fragment of Moon rock gathered during the Apollo 14 mission.

Auger electron spectroscopy (AES) is highly effective for mapping surface composition primarily because it utilizes an electron beam that is significantly easier to focus than X-rays. This capability allows for the creation of a high-intensity, small-diameter beam, which is essential for scanning and mapping the surface of a material.1

Furthermore, AES instrumentation is designed for rapid analysis, which is a practical necessity for scanning surfaces as the beam moves across the sample. While this speed can result in a sacrifice of spectral resolution, the technique's ability to provide high sensitivity—due to the intensity of the focused electron beam—makes it an ideal tool for determining the chemical composition of a surface. When combined with ion sputtering, this focused beam also enables effective depth profiling, allowing researchers to analyze successive layers of a material.12