Quantification of surface excitation effects on the EPES-determined IMFPs for GaN and SiC

Abstract

Surface electron inelastic excitations, a consequence of electron surface interaction, effect substantially the measured peak intensities, or peak areas, in surface-sensitive electron spectroscopies, and distort the quantitative information. To obtain reliable quantitative information from the electron spectra, the measured intensities and/or peak areas should be corrected for these effects. In the present work, we investigated, quantitatively, the influence of surface excitations on electron inelastic mean free paths (IMFPs) determined by elastic peak electron spectroscopy (EPES). We used IMFPs obtained from the previous EPES measurements of the electron elastic backscattering probability for GaN, SiC, and the Ni standard in the energy range 200-2000 eV. Calculated surface excitation parameters (SEPs) of both incident and emitted electrons were evaluated using the formulae of Chen, Tu et al., and Werner ef al., and applied for correcting the EPES IMFPs. These corrected values were compared with those predicted by the TPP-2M formula. We found that implementation of the surface excitation correction improved agreement between the resulting IMFPs for selected wide-band semiconductors and the TPP-2M values. The extent to which the IMFPs measured by EPES differ from the corresponding bulk values (on account of surface excitations) was found to depend on the semiconductor material with finite surface. The results also clearly demonstrated the importance of accounting for surface excitations for accuracy of the measured IMFPs. Copyright © 2008 John Wiley & Sons, Ltd.