a-SiCx:H (amorphous SiCx:H) and a-Si:H (amorphous Si:H) thin films were deposited under control of the reaction gases SiH4 + CH4 and SiH4 + H-2 by plasma enhanced chemical vapor deposition, respectively. The microstructure of as-deposited a-SiCx:H and high temperature annealed alpha-SiCx:H (6H-SiCx:H), nc-Si:H (nano-crystal Si:H) thin films were investigated by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy and ultraviolet-visible spectroscopy. The multi-layer structure of the samples was examined by cross-section transmission electron microscope. The photoluminescence (PL) properties of the samples measured by time-resolved spectroscopy at room temperature showed that the maximum PL intensity and the minimum PL decay time were obtained for the sample annealed at 900 degrees C. Typical decay times of the samples were determined to be 100 ps and 10 ns by fitting with the use of a bi-exponential function. The latter decay time of our samples closes to the decay time of direct band gap semiconductor: but nearly one thousand time, larger than that of porous Si, which was ascribed to the quantum confinement effect. (c) 2005 Elsevier B.V. All rights reserved.