Evolution of photoluminescence from Si nanocrystals embedded in a SiO_2 matrix prepared by reactive pulsed laser deposition

摘要

Photoluminescence (PL) properties of SiO_x thin films deposited by pulsed laser ablation of Si in a reactive oxygen ambient and annealed in a nitrogen atmosphere were studied at room temperature. Raman spectroscopy, Fourier transform infrared spectroscopy, and optical transmission measurements were used to characterize the deposited films before and after annealing and complement the PL studies. Strong PL due to quantum confinement was observed at room temperature from Si nanocrystals with an average diameter of approximately 5 nm at 325-nm light excitation. An apparent dependence of PL on the oxygen pressure for film deposition was observed. A detailed analysis of the effects of the annealing temperature revealed a significant PL evolution in luminescence intensity, spectrum profile, peak position, and spectrum range with the annealing temperature ranging from 300 to 1200 ℃. Structural variations induced by thermal annealing of the films deposited at different oxygen pressures were also discussed on the basis of their correlation with the PL evolution.