New intrinsic defect in as-grown thermalSiO2on (111)Si

K-band electron-spin resonance (ESR) has revealed an isotropic signal of g=2.002 46±0.000 03 in as-prepared ${\mathrm{SiO}}_2$ thermally grown on (111)Si in dry ${\mathrm{O}}_2$ at 700–860°C. The spectrum comprises a symmetric central signal of peak-to-peak width Δ${\mathrm{\beta }}_{\mathrm{pp}}$=1.0 G amid a ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ hyperfine doublet of splitting ${\mathit{a}}_{\mathrm{hf}}$=16.1 G. The salient ESR features point to an intrinsic defect in ${\mathrm{SiO}}_2$ characterized by an unpaired spin occupying an effectively nearly pure s state, which is not primarily localized at a Si site while exchanging a ${}_{}{}^{29}{}_{}{}^{}\mathrm{Si}$ superhyperfine interaction with three equivalent neighboring Si sites.