A reaction of silicon nanowires (SiNW) with methane and hydrogen has been performed to produce a thin coating layer of cubic silicon carbide (beta -SIC) using an ion beam deposition technique. High resolution transmission electron microscopy (HRTEM) showed that silicon oxide shells originally cladding the as-grown SiNW were removed and replaced by a thin layer of nano-sized crystals of beta -SiC. This has led to stable photoluminescence (PL) observed from the SiC-coated SiNW with high efficiency almost tripled as compared with that before SiC coating.