Hydrogenated microctystalline silicon-carbon films have been grown at low substrate temperature in a plasma enhanced chemical vapour deposition system by silane-methane gas mixtures highly diluted in hydrogen. The effects of the RF power on the film properties and on the amorphous to crystalline phase transition have been investigated in the 15-100 W range. Microcrystalline films are composed of Si crystallites dispersed in an amorphous silicon-carbon matrix. The increase of RF power causes the decrease of the crystalline fraction and the increase of carbon content. Microcrystalline samples with higher dark conductivity are deposited at lower RF power. Films deposited at RF power w >= 25 W exhibit a visible PL luminescence at room temperature. (c) 2005 Elsevier B.V. All rights reserved.