Flow of nanoparticles in a reactor fabricating solar cells

Solar cells have been made from hydrogenated amorphous silicon (a-Si:H) films. The films including Si nanoparticles by 3% in volume fraction have been found to possess the best properties. In order to find the method to control this volume fraction, the flow of Si nanoparticles in the source gases H2 and SiH4 is examined for a chemical vapor deposition reactor by use of the direct simulation Monte Carlo method. For the operating conditions considered here, the flow of nanoparticles has a promising property; the flux distribution of nanoparticles on the wafer is uniform, in particular, for smaller nanoparticles. The flux is nearly proportional to d3-3.5, where d3 is the diameter of nanoparticles. The flux is independent of the flow rate of carrier gas and is proportional to the total pressure.