Surface excitation effects in electron spectroscopy
AbstractAnalysis for surface chemistry uses electron spectroscopy: AES, XPS and REELS. The excitation and electron emissionprocesses are affected by the competitive surface excitation. Impinging and escaping electrons suffer losses in the solidsurface region, producing surface plasmons. The surface excitation is characterized by the surface excitation parameter P se .A new experimental procedure is described for the determination of P se . It is based on REELS–EPES, using the elastic peakas reference. The procedure is valid for materials having surface and volume plasmon loss peaks, like Si, In, and Sb. It canbe applied for estimating P se on materials exhibiting a surface loss peak decreasing with energy, like Ag. The ratio of theintegrated surface and volume loss peaks is composed and compared with the elastic peak. Experimental results in theEs0.2–5 keV energy range are presented for several solids. q2001 Elsevier Science B.V. All rights reserved. Keywords: Electron spectroscopy; Surface chemistry; Excitation