P-b1 interface defect in thermal (100)Si/SiO2: Si-29 hyperfine interaction

An optimized electron spin resonance study has resulted in the observation of the full angular dependence of the hyperfine interaction spectrum associ ated with the unpained electron of the P-b1 point defect at the thermal (10 0)Si/SiO2 interface, showing that the dominant interaction arises from a si ngle Si-29 isotope. The hyperfine tensor exhibits nearly axial (weakly mono clinic I) symmetry with A(parallel to) (parallel to[211])=167+/-3 G and A(p erpendicular to)=107 +/-4 G. Molecular-orbital analysis indicates that the unpaired electron resides for similar to 58% in a single unpaired Si hybrid orbital, found to be 14% s like and 86% p like, with the p orbital pointin g closely along a [211] direction at 35.26 degrees with the [100] interface normal. If O is excluded as an immediate part of the defect, the results e stablish the kernel of the P-b1 defect as a tilted (similar to 22 degrees a bout [0(1) over bar 1]) asymmetric, likely strained, Si(3)drop Si. unit. Li ke P-b and P-b0, P-b1 is a prototype Si dangling bond defect. All available structural information may, in principle, be compatible with the moiety be ing incorporated as part of a defected strained Si-Si dimer configuration a t slightly subinterfacial position. The dimer has previously been advanced as a natural building block in matching SiO2 to (100)Si. [S0163-1829(98)064 40-6].