NEW INTRINSIC DEFECT IN AS-GROWN THERMAL SIO2 ON (111)SI

K-band electron-spin resonance (ESR) has revealed an isotropic signal of g = 2.00246 +/- 0.00003 in as-prepared SiO2 thermally grown on (111)Si in dry O2 at 700-850-degrees-C. The spectrum comprises a symmetric central signal of peak-to-peak width DELTA-B(pp) = 1.0 G amid a Si-29 hyperfine doublet of splitting a(hf) = 16.1 G. The salient ESR features point to an intrinsic defect in SiO2 characterized by an unpaired spin occupying an effectively nearly pure s state, which is not primarily localized at a Si site while exchanging a Si-29 superhyperfine interaction with three equivalent neighboring Si sites.