Annealing effect on native-oxide/Si(111) interfaces studied by second-harmonic generation

Structural changes in native-oxide/Si(111) interfaces caused by annealing in an ultrahigh vacuum were studied by using optical second-harmonic generation (SHG). The SHG intensity increased with annealing temperature. However, this increased SHG was then decreased by supplying atomic hydrogen to the interface at room temperature. This indicates that the increase in SHG was caused by the interface dangling bonds, which are easily terminated by hydrogen. Besides SHG, x-ray photoelectron spectroscopy indicated that annealing changed the stoichiometry of the interfacial suboxide layer. After annealing, the amount of stoichiometric SiO₂ increased. Thus, annealing made the stoichiometry SiO₂-like, while the accompanying stress increase was released by dangling-bond creation at the interface.