Hydrogenated micro-crystalline silicon (pe-Si:H) thin films, with similar crystalline volume fraction (Xc) and deposition rate (R-d), were prepared by hot-wire chemical vapor deposition (HWCVD), rf plasma-enhanced CVD (PECVD), plasma-assisted HWCVD (P-HWCVD) and two-step hydrogen dilution (S-H) HWCVD. The influence of plasma and two-step SH on nano-structure of mu c-Si:H films was studied by using synchrotron radiation small-angle X-ray scattering (SAXS) combined with Fourier transform infrared spectroscopy (FTIR) and flotation density measurement. Compared with the HWCVD sample, the void fraction and mean size of micro-voids were reduced by plasma and two-step S-H. The anisotropic growth character was detected in mu c-Si:H films. (c) 2005 Elsevier B.V. All rights reserved.