Si nanocrystals-SiOx films on Si substrates have been prepared by evaporating Si or SiO in the residual gas of the : system or in an oxygen atmosphere by introducing oxygen into the deposition chamber. Films with different oxygen concentration and different Si crystallite size were obtained by changing the substrate temperature and the oxygen partial pressure. It is observed that only the films prepared by evaporating SiO in an oxygen atmosphere are photoluminescent at room temperature. The possible mechanism for the luminescence is discussed, according to the results of X-ray photoelectronic spectroscopy (XPS), infrared (IR) spectra and X-ray diffraction (XRD) measurements.