In this work results on the study of the physical and optical properties of silicon rich SiOxNy thin films are presented. The films were deposited by the plasma enhanced chemical vapor deposition technique at low temperature ( approximate to 320 degreesC) using nitrous oxide and silane as precursor gases. The films were thermally annealed at 750 and 1000 degreesC, at low pressures (10(-2) Pa) and in N-2 ambient for different annealing times. The samples were characterized through Fourier-transform infrared spectroscopy, Raman scattering and photoluminescence (PL). Raman spectra for all samples show a band approximately at 480 cm(-1), related to amorphous silicon. The spectrum for the sample with the highest silicon content, heat treated at 1000 degreesC also presents a band at 520 cm(-1), related to microcrystalline silicon. Finally, PL experiments showed the presence of visible luminescence for the as-deposited samples in the region between 1.5 and 2 eV, attributed to defects (at higher energies) and to the presence of small variable size amorphous silicon clusters embedded in the dielectric matrix. High temperature annealing substantially decreases the PL intensity, result attributed to increased cluster size and crystallization. (C) 2003 Elsevier Science B.V. All rights reserved.