Electron spin resonance, Raman scattering, photoluminescence and absorption studies were made of Si+ ions which had been implanted into silica glasses and thermally-grown SiO2 films on Si wafers. In as-grown Si-implanted films, paramagnetic defects in the form of Si-E' and non-bridging O hole centers were detected by electron spin resonance. A luminescence band which was centered at 650nm was observed in these samples. The E' and non-bridging O hole center defects were annealed out of samples that were heated to above 500C, but Si dangling bonds in the form of Pb centers were observed. In films that were annealed above 800C, Si nanocrystals with sizes of between 1 and 5nm were formed; as detected by transmission electron microscopy. A red photoluminescence band above 700nm, and a Si-phonon band at 510/cm, gradually evolved as a function of the annealing temperature. Observation of a Si-phonon mode, with a 15/cm shift in the peak-position with respect to the bulk, confirmed the presence of Si clusters in the annealed ion-implanted SiO2 films and silica glasses. This red photoluminescence band was attributed to excitonic recombination in Si nanocrystals. The peak position of this photoluminescence band was found to shift with excitation wavelength. The shift in the photoluminescence spectra as a function of excitation energy was explained in terms of emission from Si particles of a certain size that were excited by the incident energy. An energy band-gap distribution due to a size distribution was used to model the photoluminescence spectra at each excitation energy.

Characterization of Si+ Ion-Implanted SiO2 Films and Silica Glasses. S.Guha: Journal of Applied Physics, 1998, 84[9], 5210-7