Electronic properties of the Si/SiO2 interface from first principles

Unoccupied oxygen p-projected densities of states, calculated from first pr inciples in a model Si/SiO2 interface, are found to reproduce trends in rec ent atomic resolution electron energy-loss spectra [D-A. Muller et al., Nat ure (London) 399, 758 (1999)]. The shape of the unoccupied states and the m agnitude of the local energy gap are explicitly related to the number of O second neighbors of a given oxygen atom. The calculated local energy gaps o f the oxide become considerably smaller within 0.5 nm of the interface, sug gesting that the electronic properties do not change abruptly at the interf ace.