Evidence of a photon effect during the visible laser-assisted deposition of polycrystalline silicon from silane

Silicon dots have been produced by the decomposition of silane on Si layers deposited on quartz plates and irradiated by a cw Ar+ laser beam. The vertical deposition rate of Si dots was investigated as a function of irradiation time, output laser power, and silane pressure. The Si layer on quartz was first irradiated with the laser beam penetrating through the transparent quartz plate (back irradiation). The deposition of Si dots occurred by pyrolytic decomposition of ‘‘cold’’ silane molecules impinging on the laser heated area. When the surface of the Si layer on quartz was directly irradiated with the visible laser beam (front irradiation), the deposition of Si dots was accomplished at lower temperatures and involved an interaction of photons with reactive species. The kinetics of this photon-aided process is surface controlled and characterized by an apparent activation energy of about 38 kcal mol−1