Electron-Excited Core Level Spectroscopies

Abstract

This chapter deals with electron-excited core level spectroscopies for surface analysis. We shall mainly discuss the methods following the pattern “electron in-electron out” but, where appropriate, also those according to “electron in-photon out” or vice versa. The former group comprises Auger Electron Spectroscopy (AES), Ionization Loss Spectroscopy (ILS), Disappearance Potential Spectroscopy (DAPS), Auger Electron Appearance Potential Spectroscopy (AEAPS). The latter group includes Soft X-ray Appearance Potential Spectroscopy (SXAPS), Electron Microprobe Analysis (EMA) and X-ray excited Electron Appearance Potential Spectroscopy (XEAPS). The level of sophistication for these methods is quite different, mainly for historical reasons. It ranges from very recent methods with not yet fully explored potentials like DAPS, to rather old methods which have only recently been revived, like SXAPS. Others, like AES, are based upon well-known effects and are increasingly used in a wide range of applications in research and industry. The degree of theoretical understanding is quite different, too. The emission of characteristic X-rays and of Auger electrons by free atoms can be considered as being relatively well understood. Theoretical work on the influence of solid state effects on these phenomena is in progress. In contrast, for the threshold spectroscopies the detailed theoretical interpretation of the measured spectra is just at the beginning. Nevertheless, all these methods will prove valuable for the elemental and chemical analysis of surfaces.