EPR linewidth studies of unpaired electrons at the Si-SiO2 interface

Electron paramagnetic resonance studies of the dangling bonds (P/sub b/ centers) at the (111) Si-SiO2 interface are presented. In particular the angular variation in the P/sub b/ Zeeman resonance is dominated by Zeeman line broadening effects which could arise from strain within the silicon at the interface. The dipolar contribution to the observed linewidth is less than that expected assuming a random distribution of dangling bonds on an atomically flat (111) Si-SiO2 interface. This observation tentatively suggests that the dangling bonds are distributed with enhanced separation. Such an effect might occur if the dangling bond formation results from the release of strain energy from a localized region at the interface. Pulsed ruby laser irradiation of the Si-SiO2 interface at energies above the threshold for melting of the silicon increases the dangling-bond concentration by a factor of 10 and produces an angular variation in the observed linewidth which is consistent with planar dipolar broadening effects