Si1-xCx films with varying ratio of carbon to silicon (C/Si) were fabricated by magnetron co-sputtering from a combined C and Si target. The composition in films was changed by adjusting the ratio of sputtered target's area between C and Si. Analysis of X-ray photoelectron spectroscopy for as-deposited films shows that C/Si atomic ratios of our films have ranges of 0.33-1.02. Thermal annealing of as-deposited films was carried out at various temperatures from 800 to 1100 degrees C in a conventional furnace. Fourier transform infrared spectra show a shift of Si-C stretching peak towards higher wavenumbers from similar to 737 cm(-1) to similar to 800 cm(-1) with increasing annealing temperature. From the results of Raman spectroscopy, X-ray diffraction and transmission electron microscopy, it was found that the dominant type of nanocrystals changes from Si to SiC in the films annealed at 1100 degrees C when the C/Si atomic ratio increases from 0.33 to 1.02. (c) 2007 Elsevier B.V. All rights reserved.