Formation and oxidation of Si nanoclusters in Er-doped Si-rich Si O x

Abstract

The mechanisms for the formation and oxidation of Si nanoclusters (Si-ncls) are elucidated by means of the study of their effects on the photoluminescence of Er in Er-doped Si-rich SiO𝑥 (𝑥<2) films. We find that the light emission of Er is the most intense in films with a Si concentration of ∼40% after annealing at 875°C in an argon ambient, which yields an optimum Si-ncl size. The nucleation rate of Si-ncls increases with temperature, however, they stabilize around a critical size which increases with annealing temperature. We determine that the activation energy for the formation of Si-ncls is 1.4±0.5eV. During annealing in an oxygen ambient Si-ncls are oxidized. The resultant oxide reduces the efficiency of energy transfer from them to Er ions and thus the light emission of Er. The activation energy for the oxidation is 1.06±0.03eV. The authors thank Dr. W. N. Lennard for his help with RBS measurements. This work is supported by the Natural Sciences and Engineering Research Council of Canada, Ontario Centers of Excellence Inc., Photonics Research Ontario, and the Ontario Research and Development Challenge Fund under the Ontario Photonics Consortium.