Research On Properties Of Silicon Films Prepared By Hot-wire Chemical Vapor Deposition

The silicon films solar cells have been concerned in the field of PV at present. Compared with crystal silicon solar cells and polysilicon solar cells, the silicon-based thin film solar cells have less silicon materials consumption and much lower cost, especially, the application of low-cost substrates makes it more competitive in cost-control. At the same time, hydrogenated silicon film attracts extensively attention due to its application on many kinds of microelectronic deviees, such as infrared imaging system, and thin film transistor. Hot-wire chemical vapor deposited (HWCVD), or catalytic-CVD, is a low temperature Si film preparation technology which is widely used to deposit a-Si:H and poly-Si films, due to many advantages compared with other methods, including being much simpler and easier to adopt for large-area deposition at a lower cost, low deposition temperature and high deposition rate.Based on above reasons, the investigation of polycrystalline silicon thin film have great significance. we use hot-wire chemical vapor deposition (HW-CVD) prepared silicon thin films, and investigate the groth and the structure property of the silicon films. The following studies have been finished:A structure transformation from amorphous phase to crystalline phase has been observed when increasing the filament temperature from 1600℃to 1650℃. In order to explain this phenomenon, a new model of H radical is established. From the analysis about this model, the probability ball represents the probability of the appearance of H radicals. And the volume of probability ball is influenced by the filament temperature. Therefore, according to combination with experimental and model, the crystallization of the samples is determined by both the probability ball and the location of samples. It is found that the model can explain the phenomena very well.Hydrogenated nanocrystalline silicon films were deposited onto the glass substrates at different substrate temperatures (140℃-400℃). The effects of the substrate temperatures on the structural properties were investigated. With increasing the substrate temperature(<250℃), the crystalline volume fraction increased, but decreased for the further increase in substrate temperature. The maximum crystalline volume fraction of the silicon films was about 74% at the substrate temperature of 250℃. The continuous transition of the film structures from columnar to agglomerated structure was observed with an increase in substrate temperature. The optical band gaps of the grown thin films declined and dark electrical conductivity increased with increasing substrate temperature, respectively.