Thermal plasma spray of silicon has large potential for economic impact in the semiconductor and solar power industries. By post processing a thermally sprayed silicon deposition using directional re-solidification, impurities in the substrate can be controlled. We used a Thermach gun and powder feeder (SG100 and AT-1200, respectively, Appleton, WI), to deposit silicon onto steel samples. These samples were optically heat treated up to their melting point in order to increase crystal grain sizes. The depth and microstructure of the melted region was analyzed through imaging of the cross-sectioned samples. Directional re-solidification also had an effect on the impurity concentration along the depth sample. Control of impurities is demonstrated through this heat treatment and analyzed using SIMS and Laser Ablated ICP-MS. Understanding and controlling the impurity concentration has important implications in producing coatings in the solar industry as well as wafer processing equipment in the semiconductor industry.

Silicon based coatings are showing great promise for power applications in the semiconductor, target, and solar industries. In order for thermal plasma spraying of silicon to continue to have an industrial impact in these industries, careful investigations into the deposition properties must be undertaken. We used a Thermach gun and powder feeder, to deposit silicon onto 100 mm x 50 mm x 1.6 mm steel samples. Coating cross-sectioning and image analysis was performed in order to evaluate the coating’s microstructure and porosity. Mechanical property measurements consisted of hardness testing on the coating cross sections. In addition, scanning electron microscopy and optical microscopy were conducted. These results combined for an analysis into the deposition properties of silicon coatings using various particle sizings, plasma power, and spray distances. Correlations between these input parameters and their effect on the microstructure are critical to semiconductor depositions of silicon.