Energy Barrier for Valence Electrons at SiO2/Si(111) Interface

By decreasing probing depth down to 0.41 nm, the energy loss of O 1s photoelectrons with threshold energy of 3.5 eV, which was equivalent to excitation energy required for direct interband transition at G point in energy band structure of Si, was observed even through 1.12-nm-thick oxide film. It was found, considering penetration of electronic states from Si substrate into SiO2 in the analysis of thickness dependence of energy loss of O 1s photoelectron caused by the direct interband transition, that SiO2/Si interface exists in the oxide located effectively 0.61 nm away from nominal interface defined with atomic structure. 22 refs.