Defect formation in amorphous SiO2 by ion implantation:: Electronic excitation effects and chemical effects

Intrinsic defect formation in amorphous (a-) SiO2 by ion implantation was examined with emphasis upon electronic excitation effects and chemical reaction effects, 10 MeV proton beam and boron beam irradiated silica platelets to examine electronic excitation effects and chemical reaction effects. In case of H+-implantation the depth profile of Si-Si bonds, E' centers or peroxy radicals (PORs) was close to that of electronic energy loss. Interstitial O-2 molecules were identified by their photoluminescence spectra and their concentration was larger than that of peroxy radicals (PORs), The total concentration of the Si-Si bonds and E' centers was comparable to that of the interstitial O-2 and PORs, These results provide an experimental evidence that Frenkel defect formation of oxygen vacancies and interstitial ions occurs in a-SiO2 by electronic excitation. The concentration of Si-Si bonds was approximately a linear function of the ion acceleration voltage. Implantation of boron gives results which totally differ from those in the proton case, i.e., the depth profile of the Si-Si bond; which is the predominant defect, was similar to that of implanted ions, and the concentration ratio of Si-Si bonds relative to implanted ions was close to unity and the ratio was almost independent of the acceleration voltage, It is evident that implanted boron ions, which come to rest, react chemically with oxygens in the lattice to form B-O bonds, leaving Si-Si bonds at concentrations comparable to those of implanted ions. (C) 1998 Elsevier Science B.V. All rights reserved.