In this work, the various chemical stoichiometry (O/Si ratios) of silicon-rich SiO2 (SRO) thin films were deposited and then annealed by rapid thermal annealing (RTA) to form SiO2-matrix silicon nanocrystals (Si-NCs). The effects of the O/Si ratios on the structural properties of SRO thin films were investigated systematically using Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Results showed that the micro-structure of as-deposited SRO thin films with higher O/Si ratios hindered formation of Si-Si-4 clusters, Si clusters and Si rings, then hindered the phase separation and the crystallization of annealed thin films. When the O/Si ratios was increased from 0.7 to 1.5, the crystalline temperature was increased from 900 degrees C to 1000 degrees C, the crystalline fraction of the 1000 degrees C-annealed thin films was reduced from 39.4% to 22.7%, the average Si-NC size was reduced from 3.8 nm to 3 nm, and the residual stress was increased from 1.9 GPa to 2.8 GPa, respectively. The changes in micro-structure were most possibly due to the fact that the different amount of Si-O bonds in the as-deposited thin films with various O/Si ratios. (C) 2015 Elsevier B.V. All rights reserved.