Preparation,characterization And Application Study Of Silicon Nanowires And NiO Coated Silicon Nanowires

Since 1990's, tremendous attention has been paid to the preparation, characterization and application of low dimensional nanomaterials. Silicon nanowires and its related one-dimensional nanostructure become the intensive focus of research because of their unique properties in physics and chemistry compared to with their bulk counterparts and is considered to be the ideal candidate of functional units in fabricating future electronic, optoelectronic and electromechanical devices with nanoscale dimensions due to the fact that they are compatible with modern silicon IC technology. In this dissertation, we devote the most attention to several pivotal questions of silicon based nanostructures, such as fabrication, characterization and application in energy conversion and storage. The major results are described as follows:Firstly, single-crystalline silicon nanowires (sc-SiNWs) arrays were fabricated via metal-assisted chemical etching from single-crystalline silicon wafer. The structure and morphologies of sc-SiNWs are characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy, respectively. On the basis of deeply understanding the growth mechanism of metal-assisted chemical etching method, silicon nanowires were successfully fabricated through modified metal-assisted chemical etching from multicrystaline silicon wafer. These results are of vital importance for SiNWs'low-cost and large -scale application.Secondly, large-area SiNWs were fabricated from commercial solar-grade mc- Si wafer through modified metal-assisted chemical etching. The SiNWs were characterized by SEM and ultra-violet (UV)-visible spectrophotometer. We found that the length of the Si nanowires with diameter about 35–550nm is linearly proportional to the etching time. The results of diffuse reflective spectra from UV to visible indicate that the nanowires surface acts a tunable antireflection layer via adjusting the nanowires length. Excellent antireflection properties of SiNWs textured surface with etched time more than 45 min are observed. The value of reflectivity less than 9% is realized in the 190-800 nm, Our result have application in construct excellent antireflection textured surface of multicrystaline silicon solar cell.Thirdly, highly ordered NiO coated Si nanowire array films were fabricated as electrodes for high performance lithium ion battery via depositing Ni on electroless-etched Si nanowires and subsequently annealing. The structures and morphologies of as prepared films are characterized. Electrochemical tests indicate that coated NiO can be selected to be electrochemically active and crystalline Si cores function as a stable mechanical support and an efficient electrical conducting pathway. The hybrid nanowire array films exhibit superior cyclic stability and reversible capacity. The reversible capacity of 606.13 mAh g?1 is obtained when the cell is cycled at a rate of 50 mA/g after the 30th cycle. Owing to the ease of large-scale fabrication and superior electrochemical performance, these hybrid nanowire arrays will be promising anode materials for high performance lithium-ion batteries.