Detail structural characterizations of the nC-Si/SiOx:H films prepared from low temperature (300 degrees C) SiH4 plasma, have been performed using various spectroscopic and microscopic probes, e. g., IR spectroscopy, ellipsometry, scanning electron microscopy and atomic force microscopy. The growth structure has been probed by Bruggeman effective medium approximation fitting to the ellipsometry data, considering a three-layer growth model, which has been identified by FESEM studies. It has been observed that with the reduction in pressure (p) the overall crystallinity improves along with the lowering in the incubation layer thickness, and the reduction of void fraction in the bulk as well as in the growth zone and surface layer. The maximum crystallinity in the bulk has been identified at p = 0.6 Torr, corresponding to the lowest roughness on the surface. Oxygen incorporation has been found to be favored at lower gas pressure in the plasma, along with simultaneous dehydrogenation of the silicon network which remains the key criteria for attaining enhanced nanocrystallinity. Plausible formation mechanism of the nC-Si/SiOx: H structure, activated by chemical reactions occurring in the He diluted (SiH4 + CO2) plasma has been investigated. (C) 2012 Elsevier B. V. All rights reserved.