Annealing Effects on Cathodoluminescence Properties of SiOx Films Deposited by Radio Frequency Sputtering

概要

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The effects of high-temperature thermal annealing on cathodoluminescence (CL) spectra in SiOx ($0.9 \leq x \leq 1.87$) 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 °C. One of features in the CL spectra for the films annealed at 1100 °C is a peak at a photon energy of ${\sim}2.7$ 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 $n = 2{\mbox{--}}5$, 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 Si2 clusters to the CL spectra are dominant, whereas those of the Sin clusters with $n > 3$ are considerably small.
2011-01-25