We investigated the effect of Xe dilution of silane on structural, optical and electrical properties of nanocrystalline Si films deposited by HW-CVD. With increase in Xe dilution of silane nanocrystalline-to-amorphous transition or amorphization has been observed in nanocrystalline Si films. The amorphization has been confirmed from dark and photoconductivity measurement, Raman spectroscopy, low angle XRD and atomic force microscopy analysis. The FTIR spectroscopy analysis showed that with increase in Xe dilution of silane, in addition to di-hydrogen [Si-H2] and poly-hydrogen [(Si-H2)n] complexes, hydrogen incorporated in these films in mono-hydrogen [Si-H] bonded species. The hydrogen content was found < 5 at. % over the entire range of Xe dilution of silane studied and it increases with increase in Xe dilution of silane. On the other hand, ETauc and E04 show decreasing trend with increasing Xe dilution of silane. The ETauc decreases from 2.4eV to 1.9eV whereas E04 decreases from 2.9eV to 2.3eV. The optical band gap values estimated from E04 method are found higher than ETauc values calculated from Tauc’s method. Finally, it has been concluded that Xe dilution of silane in HW-CVD enhances the deposition rate but has adverse effect on the crystallinity of nanocrystalline Si films.