Theoretical studies of Si-O and Si-N bonding arrangements on vicinal Si(111) wafers

Abstract

The bonding at O (N) atom-terminated dangling bonds at steps in the 112¯ direction is investigated by ab initio cluster calculations. We find that one Si atom and three O (N) atoms, i.e., a ${\mathrm{SiO}}_3$ (${\mathrm{SiN}}_3$) group, can bridge three dangling bonds such that the strain induced at the step by these bonding groups is negligible. The results help to explain the significant changes in the interface trap density ${\mathit{D}}_{\mathrm{it}}$ and the relative phase of the onefold and threefold contributions to the second-harmonic generation from oxide-terminated vicinal Si surfaces formed by thermal oxidation at 850 °C following annealing at temperatures ∼1000 °C, where Si-O atom arrangements can readily occur.