VISIBLE PHOTOLUMINESCENCE IN SI+-IMPLANTED SILICA GLASS

We have investigated visible photoluminescence excited by Ar-ion laser (488 nm, 2.54 eV) at room temperature from Si+-implanted silica glass, as-implanted and after subsequent annealing in vacuum. We found two visible luminescence bands: one peaked around 2.0 eV, observed in as-implanted specimens and annealed completely after heating to about 600-degrees-C, the other peaked around 1.7 eV observed only after heating to about 1100-degrees-C, the temperature at which Si segregates from SiO(x). It was found that the 2.0 eV band anneals parallel to the E' centers, as detected by electron spin resonance studies. It was also found that Raman lines around 520 cm-1, due to Si-Si bonds, grow and that interference patterns are induced by annealing Si+-implanted silica glass. Based on these studies, we ascribe the 2.0 eV band to the electron-hole recombination in Si-rich SiO2 and the 1.7 eV band to the electron-hole recombination in the interface between the Si nanocrystal and the SiO2 formed by segregation of crystalline Si from SiO(x).