Abstract
The effects of high-temperature thermal annealing on cathodoluminescence (CL) spectra in SiOx (0.9 <= x <= 1.87) films prepared by radio-frequency sputtering are investigated. The CL intensities for the as-deposited films are weak but they increase after thermal annealing at 900 and 1100 degrees C. One of features in the CL spectra for the films annealed at 1100 degrees C is a peak at a photon energy of similar to 2.7 eV with an asymmetric tail on the lower energy side. In order to analyze the spectral features, optical transition energies are calculated for Sin clusters with n = 2-5, embedded in a SiOx matrix, by ab initio molecular orbital calculation. In addition, the probabilities of formation are statistically estimated for those Si clusters under the assumption of a chemically ordered random network for the SiOx network. The comparison of the experimental results with the calculated transition energies and the statistics of the Si clusters suggests that a contribution of the Si-2 clusters to the CL spectra are dominant, whereas those of the Si-n clusters with n > 3 are considerably small. (C) 2011 The Japan Society of Applied Physics