AUGER ELECTRON SPECTROSCOPY

Abstract

Auger electron spectroscopy (AES) is a nondestructive core-level electron spectroscopy for semi-quantitative determination of the elemental composition of surfaces, thin films, and interfaces. The popularity of this ultrahigh vacuum technique may be attributed to high surface sensitivity (an analysis depth of less than 100 Å) and a relatively low detection limit (~0.1 atomic percent). In addition to having an elemental coverage from lithium to uranium and beyond, AES has the ability to distinguish between two elements that are close to each other in the periodic table. In addition, AES has an atomic number-dependent sensitivity that varies at most by one order of magnitude. AES chemical shifts and line shapes can also yield bonding (chemical state) information, albeit with less precision than is possible with X-ray photoelectron spectroscopy (XPS) (Chapter 11), another core-level electron spectroscopy. Auger electron spectroscopy has a depth resolution of 5–25 Å, and can be used, with simultaneous ion sputtering, for depth profiling. With a lateral resolution (< 100 Å) that is significantly better than that of XPS, scanning Auger microscopy (SAM) can be used effectively for imaging nanoscale structures and to produce two-dimensional maps of surface elemental composition. Survey Auger spectra typically take less than five minutes, providing for rapid data acquisition. Although somewhat sophisticated and expensive, Auger instrumentation is relatively simple to use and is readily available from many different commercial sources. The reasons enumerated above explain why Auger electron spectroscopy has become perhaps the most widely used surface analytical technique.