Intrinsic defect formation in amorphous SiO2 by electronic excitation: Bond dissociation versus Frenkel mechanisms

Two competing mechanisms of intrinsic defect formation in amorphous SiO2 (a -SiO2), i.e., the vacancy-interstitial (Frenkel) mechanism and Si-O bond dissociation to form silicon and oxygen dangling bonds, were compared under γ -ray electronic excitation. The Frenkel mechanism was found to be dominant. The concentrations of both kinds of defects strongly correlate with the degree of the structural disorder of a -SiO2, providing experimental evidence that both types of intrinsic defect pairs are formed mainly from the strained Si-O-Si bonds. The bond dissociation mechanism is more susceptible to the structural disorder than the vacancy-interstitial mechanism.