Coating techniques of metal chambers for remote catalytic chemical vapor deposition applications

To obtain information for remote catalytic chemical vapor deposition, the authors constructed a two-chamber system in which the decomposition and deposition areas were separated. H2 molecules were decomposed on a heated tungsten filament in the first area and the H atoms produced were carried to the second area, where the absolute H-atom densities were measured by a vacuum-ultraviolet laser absorption technique. The gas pressure in the decomposition area was maintained ten times higher than that in the deposition area by mounting a diffusion barrier to prevent the possible back-diffusion of the material gases. The inner walls of the decomposition area as well as the diffusion barrier were coated with SiO2 or polytetrafluoroethene to minimize the recombination of H atoms. The H-atom density could be increased by one order of magnitude by such coatings, and it is shown that H-atom densities in the order of 1012 cm−3 can be achieved in the deposition area in the present system.