Characterization of defects formed in amorphous SiO 2 by high energy ions using electron spin resonance and optical spectroscopy

Abstract

ESR studies of amorphous silica samples irradiated by high energy heavy ions show that the paramagnetic defects formed when electronic interactions dominate are similar to those observed after γ-ray irradiation (E' centers and oxygen hole centers, or OHC). However, spectra of ion-irradiated samples exhibit specific features, due to the high density of energy deposit which is specific to heavy ion irradiation. Furthermore, the concentrations of defects cannot be interpreted from the total energy deposit alone, as the atomic number plays an important role. When the energy deposit increases, we observe a transfer from E' centers to OHC, which is also observed after annealing. This supports the concept of a “ thermal spike” reorganization phase in the wake of the incident ion. Optical spectroscopy results are consistent with ESR for E' centers, and show that the B 2 centers, which are interpreted as diamagnetic oxygen vacancies, are less abundant than the E' centers.