Hot-wire chemical vapour deposition (HWCVD) has been used to prepare both hydrogenated amorphous silicon (a-Si:H) and nano/ microcrystalline thin layers as intrinsic material at different deposition conditions, in order to establish optimum conditions where the hydrogen content would be minimal and the films would still exhibit good optical properties. Experimental data shows that by varying deposition conditions the transition to the nano/microcrystalline phase can be achieved. Transitional films in the regime tending towards the crystalline phase showed no infrared-active hydrogen. XRD analysis failed to show any discernible crystalline peaks, while Raman spectroscopy as a tool is more promising for the identification of films in changeover to the nano/microcrystalline state. (c) 2005 Elsevier B.V. All rights reserved.