PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS
Abstract
A detailed comparison of the surface sensitivity of x-ray photoemission spectroscopy for hard and soft x rays
is presented and discussed. Electron scattering parameters and their energy dependence are given for Si and
two Si spectra are analyzed: a Mg K h =1253.6 eV excited spectrum of the Si 2p and 2s lines and a hard
x-ray excited spectrum h =5925 eV of the Si 1s line. The differential inelastic scattering characteristics for
Si are extracted from reflection electron energy loss spectra taken at energies of 1500 and 4000 eV. Using these
scattering characteristics and electron mean free paths from the literature, simulated spectra are compared with
experiment. The experimental spectra are deconvoluted to give the true intrinsic line shape corresponding to
the 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 of
intrinsic and extrinsic excitations. In this way, it is found that in the case of the soft x-ray excited photoelectron
spectrum of the shallower electronic shells 2p and 2s, intrinsic plasmon creation is rather weak, and the
apparent asymmetric line shape of the spectrum might be interpreted as the fact that electron-hole pair creation
dominates the intrinsic loss spectrum, while an alternative explanation in terms of surface core level shifted
components is also proposed. For the deeper core electronic shell, probed with hard x rays, the opposite
situation is observed: while intrinsic electron-hole pair creation was not observed, a strong contribution of
intrinsic plasmon losses of about 30% was seen
