Nanostructured and thick SiC coatings have been successfully deposited on Si and graphite substrates by thermal plasma physical vapor deposition (TPPVD) using ultrafine SiC powder as a starting material. The control of processing parameters such as substrate temperature, composition of plasma gases, permits to the deposition of SiC coatings with a variety of microstructures and with various morphologies from dense to columnar. The maximum deposition rate reached 200 nm/s. Seebeck coefficient up to −480 μV/K was obtained for the non-doped coatings with stoichiometric composition. Nitrogen doping to the coatings made it possible to decrease the electrical resistivity from 10-2∼10-3 to 10-4∼10-5 Ωm and showing the maximum power factor of 1.0×10-3 Wm-1K-2 at 973 K.

This research is the first attempt at applying thermal plasma chemical vapor deposition (TPCVD) for the ultrafast deposition of Si films for solar cells. A conventional deposition process of Si films, such as plasma-enhanced chemical vapor deposition (PECVD), is capable of a maximum deposition rate of approximately 5 Å/s and it takes a relatively long time to deposit an intrinsic layer. In this paper we report a novel ultrafast deposition approach using dc-rf hybrid TPCVD. The extreme improvement of stability, controllability, and cleanliness of the process enabled the deposition of microcrystalline Si films at the ultrafast rate of over 1000 nm/s, which is about 2000 times faster than that by conventional CVD. Moreover, a minimum defect density of 7.2×1016 cm−3was achieved by post-treatment of the film in 2 Torr H2/Ar plasma. Monte-Carlo simulation and step coverage analysis suggested that the precursor is an approximately 1 nm cluster with a sticking probability of about 0.6. The success of this research will lead to the development of commercially viable technology in a roll-to-roll system in the near future, and will fundamentally change the established concepts of Si deposition technology.