Large-scale nanowires are grown on Si wafers by the catalyst-free one-step thermal reaction method in Ar/H2 mixture atmosphere at 1000℃.The x-ray diffraction and energy dispersive x-ray spectroscopy results reveal that the final nanowires are of silicon nanostructures.The field emission scanning electron microscopy shows that these self-organized Si nanowires (SiNWs) possess curly crowns with diameters varying from 10 to 300nm and lengths of up to several hundreds of micrometers.The transmission electron microscopy indicates that the nanowires are pure Si with amorphous structures.All the measurement results show that no silicon oxide is generated in our products.The growth mechanism is proposed tentatively.Silicon oxide is reduced into Si nanoparticles under the Ar/H2 mixture,which is the main reason for the formation of such SiNWs.Our experiments offer a method of preparing Si nanostructures by simply reducing silicon oxide at high temperature.Silicon nanowires (SiNWs) have higher carrier mobility,a larger surface-to-volume ratio and a longer minority carrier diffusion length than single-crystal bulk silicon materials and can bear large stress without pulverization,which make them suitable for fabricating high-performance nanoelectronic and nanophotonic devices.[12] Since SiNW-related nanodevices are compatible with the current Si-based microelectronics manufacturing process,many new nanodevices,such as field effect transistors (FET),solar cells,sensors,lithium battery and thermoelectric conversion devices,have been made in SiNWs.[2-7]