Abstract
The electronic structure of GeO2 and SiO2 has been studied by ultraviolet photoemissionspectroscopy (UPS) and electron energy loss spectroscopy (ELS) using thermally grownfilms prepared in ultrahigh vacuum (p ∼ 10−10 Torr). A consistent energy level model of both filled and empty states is constructed from the UPS and ELS data. The filled states correspond to localized bonding or nonbonding O(2p) molecular orbitals. The empty states observed in ELS correspond to excitons formed from either localized antibonding states or more extended ``conduction'' band states.