The effects of the silane concentration f on the structural, optical and electrical properties of undoped hydrogenated silicon films prepared in a plasma-enhanced chemical vapour deposition system have been studied. The electrical conductivity and Hall mobility appear to be controlled by microstructures induced by silane concentration and a clear electrical transport transition from crystalline to amorphous phase has been found when 3% < f < 4%. A two-phase model has been used to discuss the electrical properties. (c) 2004 Elsevier B.V. All rights reserved.