Optimized electron spin resonance studies led to observations of the full angular dependence of the hyperfine interaction spectrum which was associated with the unpaired electron of the Pb1 point defect at thermal (100)Si/SiO2 interfaces, thus showing that the dominant interaction arose from a single 29Si isotope. The hyperfine tensor exhibited nearly axial (weakly monoclinic) symmetry. Molecular-orbital analysis indicated that the unpaired electron resided, for some 58% of the time, in a single unpaired Si hybrid orbital which was 14% s-like and 86% p-like; with the p orbital pointing almost along a <211> direction at 35.26º to the [100] interface normal. If O was excluded from being a direct part of the defect, the results established the kernel of the Pb1 defect to be a tilted (by some 22º about <0¯11>) asymmetrical, and probably strained, Si3=Si• unit. Like Pb and Pb0, Pb1 was a prototype Si dangling-bond defect. It was concluded that all of the available structural data were compatible with its being incorporated as part of a defected strained Si-Si dimer configuration at a slightly sub-interfacial position. Such a dimer had already been suggested to be a natural building block for matching SiO2 to (100)Si.

Pb1 Interface Defect in Thermal (100)Si/SiO2 A.Stesmans, B.Nouwen, V.V.Afanasev: Physical Review B, 1998, 58[23], 15801-9