Si-rich silicon oxide (SiOx, 1 < x < 2) films were prepared by RF magnetron reactive sputtering or co-sputtering on the Si(111) substrates. X-ray diffraction patterns showed that the peak of silicon nanocrystals (NCs), separated from SiOx films, had (111) preferred orientation. The results of scanning electron microscopy indicated the Si NCs uniting into clusters. We demonstrated that the photoluminescence (PL) peaks at 650 nm was caused by defect center. In particular, we discussed the correlation between the PL and the structure of SiOx films. The mean size of the Si NCs was estimated to be about 3 nm by the PL peak position. (c) 2005 Elsevier B.V. All rights reserved.