Electronic Properties of theSi/SiO2Interface from First Principles

Unoccupied oxygen $p$-projected densities of states, calculated from first principles in a model $\mathrm{Si}/{\mathrm{SiO}}_2$ interface, are found to reproduce trends in recent atomic resolution electron energy-loss spectra [D. A. Muller et al., Nature (London) 399, 758 (1999)]. The shape of the unoccupied states and the magnitude 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 of the oxide become considerably smaller within 0.5 nm of the interface, suggesting that the electronic properties do not change abruptly at the interface.