EPR study of paramagnetic species in oxide glasses implanted with nitrogen

Abstract

The electron paramagnetic resonance (EPR) spectra of borate, silicate and phosphate glasses implanted with N + ions at two energies ( E = 80 and 150 keV) to nominal doses 2 × 10 16 and 1.5 × 10 16 cm −2, respectively, are reported. EPR measurements were performed at room temperature using a modified RE-1306 spectrometer operating at ∼ 9 GHz frequency. Molecular O 2 − ions are induced in all the glasses and their numbers are greater than those of other defects. The analysis of data shows that EPR spectra of these implanted glasses consist of several anisotropic spectra belonging to O 2 − ions. Eight spectral components are used for simulation of EPR spectra of O 2 − ions. Different combinations of these 8 components (from one to three components) with various statistical weightings were taken to obtain best-fit computed spectra for more than 100 samples. Their principal g-values range from 2.05 to 2.017 for g z from 2.01 to 2.004 for g y and from 2.0025 to 1.993 for g x . The highest content of O 2 − ions was observed in borate glasses in the case of nitrogen implantation. This result is attributed to the sputtering loss of boron atoms in the implanted layer and the increase in relative concentration of oxygen displaced from their sites in ion-implanted layers. The well-known spectrum ‘five-lines-plus-a-shoulder’ is observed in borate glasses which is attributed to a boron oxygen hole center (B-OHC). The EPR spectrum of NO 2 molecules is observed in some glasses. The absence of these molecules in the other glasses is interpreted in terms of the formation of Si-N and P-N chemical bonds.