Optical properties of silicon oxide (SiO_x, x<2) thin films deposited by PECVD technique

Silicon oxide thin films were deposited by using a plasma-enhanced chemical-vapor deposition technique to investigate the light emission properties. The photoluminescence characteristics were divided into two categories along the relative ratio of the flow rates of SiH₄ and N₂O source gases, which show light emission in the broad/visible range and a light emission peak at 380 nm. We attribute the broad/visible light emission and the light emission peak to the quantum confinement effect of nanocrystalline silicon and the Si=O defects, respectively. Changes in the photoluminescence spectra were observed after the post-annealing processes. The photoluminescence spectra of the broad light emission in the visible range shifted to the long wavelength and were saturated above an annealing temperature of 900° or after 1 hour annealing at 970°C. However, the position of the light emission peak at 380 nm did not change at all after the post-annealing processes. The light emission intensities at 380 nm initially increased, and decreased at annealing temperatures above 700°C or after 1 hour annealing at 700°. The photoluminescence behaviors after the annealing processes can be explained bythe size change of the nanocrystalline silicon and the density change of Si=O defect in the films, respectively. These results support the possibility of using a silicon-based fight source for Si-optoelectronic integrated circuits and/or display devices.