Researches On The Si/SiC Nanocomposite Films And Preparation Of Si Nanowires By Thermal Evaporation

In this research, silicon based nanomaterials, Si/SiC nanocomposite films and Si nanowires, were prepared and investigated.Si/SiC nanocomposite films with Si nano-particles in the SiC matrix were prepared by using radio frequency (R.F.) sputtering techniques in two methods: multilayer by alternate sputtering and composite by co-sputtering. The samples were then annealed at different temperatures. The photoluminescence (PL) phenomenon of multilayer thin films was observed in samples annealed over 1200°C. The PL spectra showed two emission bands at about 352 nm and 468 nm, and the PL intensity increased with the increase of the annealing temperature. The blue PL band at 468 nm is related to a quantum size effect of Si nanocrystallites, while the ultraviolet (UV) PL peak band at 352 nm may be originated from the presence of the Si-O-C complex compound formed at high temperature. The PL spectra of co-sputtered thin films after annealing showed an UV PL peak band and it was possibly owing to the presence of the Si-O-C bond.Si nanowires were produced from single-crystal Si wafer without catalysts by thermal evaporation at high temperature and normal pressure. The length of Si nanowires was up to a few millimeters. High resolution transmission electron microscope(HRTEM) image showed that the nanowires were single-cystal with ultrathin amorphous surface layer and the diameter is in the range of 10-30 nm. The formation of Si-O layer on the Si wafer, the closed space, and the slow-cooling rate are key factors leading to the formation of Si nanowires. A self-induced vapour-liquid-solid (VLS) model has been used to explain the formation mechanism. The results suggest that a catalyst in the growth of Si nanowires is not essential.