Structure of microcrystalline silicon films deposited at very low temperatures by hot-wire CVD

A new technological regime for the deposition of intrinsic hydrogenated mic rocrystalline silicon (mu c-Si:H) films at very low temperatures by the Hot -Wire CVD technique is studied in this paper. The influence of the main tec hnological parameters on the structural properties of intrinsic samples is reviewed. Detrimental post-oxidation effects arising in the layers with the exposure to the atmosphere were strongly reduced by depositing the materia l at pressures lower than 1 x 10(-2) mbar. Enhanced crystalline fractions o ver 95% have been obtained at very low temperatures (T-s < 200 degrees C) b y proper tuning of the hydrogen dilution. Moreover, this low substrate temp erature has been shown to promote a decrease of the subgap absorption, whic h has been attributed to a low deep defect density related to the hydrogen passivation of dangling bonds in the grain boundaries. (C) 2000 Elsevier Sc ience S.A. All rights reserved.