Hot-wire chemical vapour deposition is a versatile technique to deposit a-Si:H and nc-Si films at higher deposition rate (similar to 5-10 angstrom/s) as compared to Plasma enhanced chemical vapour deposition (1-2 angstrom/s). We report the deposition of highly crystalline Si films at very high deposition rate (>= 40 angstrom/s) by adding methane to silane during thermal/catalytic decomposition. A series of films were deposited by varying the chamber pressure between 10 and 100 Pa at a substrate temperature of 300 degrees C and filament temperature 2000 degrees C. The hydrogen diluted silane (10% silane in hydrogen) and pure methane were used as precursors and gas flow rate ratio was kept constant at 10. Films prepared at lower pressure (<= 20 Pa) were more crystalline and do not contain any trace of carbon atoms. Bandgap was found to increase from 1.24-1.63 eV when pressure was increased. It was observed that chamber pressure plays a key role in determining the crystallinity, disorder and composition of these films. Addition of methane to hydrogen diluted silane increased deposition rate and crystallinity of Si films at low pressure (<= 20 Pa). Above 20 Pa pressure, carbon atoms signature was obtained. SiC films were obtained when pressure was > 100 Pa.