Surface sensitivity in electron spectroscopy: coherent versus incoherent scattering models

We investigate the extent of diffraction effects (coherent elastic scattering) in electron spectra measured on materials that do not exhibit perfect crystal structure, such as crystals with a high defect density, polycrystalline materials or even amorphous solids. A single scattering cluster (SSC) model was implemented to calculate photoelectron angular distributions for non-ideal crystals. As a first test, results obtained with this code were compared with a well established code for a perfect crystal. The two codes were found to give essentially identical results. Furthermore, SSC calculations of Ni2s photoelectron depth distributions averaged over crystal orientation so as to apply to an amorphous material were compared with Monte-Carlo (MC) simulations of elastic scattering, entirely based on a non-coherent scattering model. The two sets of results were semi-quantitatively consistent. (C) 2004 Published by Elsevier B.V.