Pb1interface defect in thermal(100)Si/SiO2: 29Sihyperfine interaction

Abstract

An optimized electron spin resonance study has resulted in the observation of the full angular dependence of the hyperfine interaction spectrum associated with the unpaired electron of the $P_{b1\mathrm{}}$ point defect at the thermal $\mathrm{}\left(100\right)\mathrm{}{\mathrm{S}\mathrm{i}/\mathrm{S}\mathrm{i}\mathrm{O}}_2$ interface, showing that the dominant interaction arises from a single ${}^{29}\mathrm{Si}$ isotope. The hyperfine tensor exhibits nearly axial (weakly monoclinic I) symmetry with $A_{\parallel }$ $\left(\parallel 〈211〉\right)=167\mathrm{}\pm 3\mathrm{G}$ and $A_{\perp }=107\mathrm{}\pm 4\mathrm{G}.$ Molecular-orbital analysis indicates that the unpaired electron resides for ∼58% in a single unpaired Si hybrid orbital, found to be 14% s like and 86% p like, with the p orbital pointing closely along a 〈211〉 direction at 35.26° with the [100] interface normal. If O is excluded as an immediate part of the defect, the results establish the kernel of the $P_{b1\mathrm{}}$ defect as a tilted (∼22° about 〈01¯1〉) asymmetric, likely strained, ${\mathrm{Si}}_3{\mathrm{\equiv }\mathrm{Si}}_{\mathrm{•}}$ unit. Like $P_b$ and $P_{b0\mathrm{}},$ $P_{b1\mathrm{}}$ is a prototype Si dangling bond defect. All available structural information may, in principle, be compatible with the moiety being incorporated as part of a defected strained Si-Si dimer configuration at slightly subinterfacial position. The dimer has previously been advanced as a natural building block in matching ${\mathrm{SiO}}_2$ to (100)Si.