Dipolar interaction between [111]Pbdefects at the (111)Si/SiO2interface revealed by electron-spin resonance

Abstract

A method is outlined to vary reproducibly the density of [111] ${\mathit{P}}_{\mathit{b}}$ centers (⋅Si≡${\mathrm{Si}}_3$ defects with an unpaired ${\mathit{sp}}^3$ orbital perpendicular to the interface) at the thermal (111)Si/${\mathrm{SiO}}_2$ interface (grown at ≊920 °C; 1.1 atm ${\mathrm{O}}_2$) using alternate non–Iin situR H passivation (hydrogenation in pure ${\mathrm{H}}_2$ at temperatures T=253 °C–353 °C) and degassing (high vacuum of p<${10}^{\mathrm{-}6}$ Torr at T=752 °C–835 °C). These soft thermal treatments may be randomly sequenced and do not affect the interface structure. Only the spin state (electron spin resonance activity) of ${\mathit{P}}_{\mathit{b}}$ centers is modified by bonding or releasing H. The total number of ⋅Si≡${\mathrm{Si}}_3$ defects—either passivated or not—remains unaltered and seems to be set by the initial oxidation step. The maximum ${\mathit{P}}_{\mathit{b}}$ density is about 1.5% of the Si atom sites in a (111) plane, which appears as a natural constant for the (111)Si/${\mathrm{SiO}}_2$ interface thermally grown at ≊920 °C. This [${\mathit{P}}_{\mathit{b}}$] monitoring is used as a tool to unveil the dipole-dipole (DD) influence on the K-band electron-spin-resonance spectrum of ${\mathit{P}}_{\mathit{b}}$ centers. The main effects are an overall broadening of the Zeeman resonance and the appearance of fine-structure doublets that grow with increasing concentration.