Elastic and inelastic scattering in electron momentum spectroscopy of amorphous Ge films

Electron momentum spectroscopy (an (e, 2e) experiment in the high-energy and large momentum transfer limit) is a scattering approach to the study of the electronic structure. The intensity observed in these experiment is, for an infinitely thin film, simply proportional to the spectral momentum density. For experiments using free-standing films of a more realistic thickness (100 Å or so), elastic and inelastic multiple scattering events are frequent and their influence on the observed intensity cannot be neglected. Here we study germanium films where the sp derived valence band can be measured simultaneously with the shallow, non-dispersing, 3d level. Somewhat surprisingly, the intensity of the 3d level, relative to that of the valence band, increases with film thickness. This effect is attributed to elastic multiple scattering. Monte Carlo simulations reproduce the changes in the observed intensity distributions with increasing film thickness.