Auger electron spectroscopy (AES) is a widely used technique for the analysis of surfaces, and it has application in many fields of materials science. AES is highly surface specific, and for most materials it is only sensitive to the top few monolayers. Minute amounts of material at the surface can be analyzed. Under the right conditions 10−3 of a monolayer [6.1], and in an Auger microscope as few as 104 atoms, with a spatial resolution of 20 nm can be detected [6.2]. The qualitative interpretation of AES spectra is straightforward for many materials, and all elements except for hydrogen and helium are detectable. Any radiation with sufficient energy to ionize an atomic core level will stimulate Auger electron emission, but, by convention, AES is normally understood to use an electron beam.