EELS STUDY OF SINGLE-CRYSTALLINE NIO(100)

A detailed EELS study of NiO(100) deaved in UHV has been performed to obtain new information about the origin of the insulating pp and about the nature of weak excitations within the gap. The low loss intensity of the inneratomic d-d excitations within the gap is strongly dependent on the primary energy whereas the cross section for the first excitations across the gap is approximately constant. This can be explained by different types of O 2p- Ni 3d hybridization. We assume that the first transitions across the gap are due to excitations of localized electrons in the p-d orbitals of a Ni-O cluster.