Publications in Scientific Journals:
F. Offi, W.S.M. Werner, M. Sacchi, P. Torelli, M. Cautero, G. Cautero, A. Fondacaro, S. Huotari, G. Monaco, G. Paolicelli, W. Smekal, G. Stefani, G. Panaccione:
"Comparison of hard and soft x-ray photoelectron spectra of silicon";
Physical Review B,
A detailed comparison of the surface sensitivity of x-ray photoemission spectroscopy for hard and soft x raysis presented and discussed. Electron scattering parameters and their energy dependence are given for Si andtwo Si spectra are analyzed: a Mg K h =1253.6 eV excited spectrum of the Si 2p and 2s lines and a hardx-ray excited spectrum h =5925 eV of the Si 1s line. The differential inelastic scattering characteristics forSi are extracted from reflection electron energy loss spectra taken at energies of 1500 and 4000 eV. Using thesescattering characteristics and electron mean free paths from the literature, simulated spectra are compared withexperiment. The experimental spectra are deconvoluted to give the true intrinsic line shape corresponding tothe theoretical collision statistics when interference effects between intrinsic and extrinsic scattering are neglected.The magnitude of interference effects cannot be assessed by our analysis. Within the unknown uncertainty introduced by neglecting interference effects, it is possible to determine the relative intensity ofintrinsic and extrinsic excitations. In this way, it is found that in the case of the soft x-ray excited photoelectronspectrum of the shallower electronic shells 2p and 2s , intrinsic plasmon creation is rather weak, and theapparent asymmetric line shape of the spectrum might be interpreted as the fact that electron-hole pair creationdominates the intrinsic loss spectrum, while an alternative explanation in terms of surface core level shiftedcomponents is also proposed. For the deeper core electronic shell, probed with hard x rays, the oppositesituation is observed: while intrinsic electron-hole pair creation was not observed, a strong contribution ofintrinsic plasmon losses of about 30% was seen.
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