Energy-resolved momentum densities for the valence band of a nanoscale Si single crystal

We have measured the energy-and momentum-resolved band structure, and ground state of occupation of the bands, for a crystalline silicon sample along the (100) and (110) directions. Band structures were determined directly by the technique of electron momentum spectroscopy (EMS) for a self-supporting Si membrane with a thickness of approximately 7 nm. We compare our experimental results with ab initio calculations for bulk crystalline silicon performed within the linear muffin tin orbital approximation. Qualitative agreement is seen between experiment and theory for the main valence band peak. Additional intensity is observed in the measurement on either side of the main peak and is attributed mainly to multiple-scattering events. Satellite structure could also be present in these additional features, although there is no direct evidence for this.