Controlled Growth Of Silicon Nanowires By Solid-liquid-solid Method And Their Formed Mechanism

High quality silicon nanowires (SiNWs) were grown directly from n-(111) single crystal silicon based on solid-liquid-solid(SLS) mechanism use Au or Al films as metallic catalyst. The effects of metal film thickness, annealing temperature, growth time and gas flow rate on the formation of the SiNWs were experimentally investigated. The morphology and microstructure, chemical compositions and growth crystall orientation of the SiNWs were characterized and analyzed by the scanning electron microscopy(SEM), the energy-dispersive X-ray spectroscopy(EDS) and X-ray powder diffraction(XRD). The results indicated that the optimize parameters to realize Si nanowires with high density, uniform distribution and similar direction are as follows: the thickness of Au or Al film is between 5-10 nm, the temperature is 1100℃, and the flow of N2 or Ar is 1.5L/min. The diameters and lengths of the formed SiNWs are 20-300nm and from several micrometers to sereral tens of micrometerss and some even reaching millimeter level, respectively. The room temperature photoluminescence (PL) properties of the SiNWs were observed by Xe lamp. The results shown that the SiNWs have a stronly blue luminescencent band around 400-480nm with an emission peak position at 420nm. The formed process of the SiNWs is analysized qualitatively based on microstructure thermodynamics and crystal growth kinetics.The results shown that the process of the SiNWs include that the deposit of metal catalyst, the form of Au-Si eutectic droplet alloy, there is gather in partial district of Si in Au-Si, the alloy run out the undercooled region, nucleus formation and Si were separate out form Au-Si alloy and serve as seed crystal, and the SiNWs were grown.