Deposition of undoped polycrystalline-silicon (poly-Si) films on SiO 2 using an ultrahigh vacuum chemical vapor deposition system was investigated. Poly-Si films with high crystallinity were obtained at a temperature as low as 525°C. The layer growth process was found to proceed with an activation energy of 44±2 kcal/mol, and is dominated by the desorption rate of surface-bonded hydrogen atoms. An incubation time was observed prior to the film deposition. This incubation period increased with decreasing growth temperature, resulting from slower nucleation and growth rates at lower temperatures.