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

A new technological regime for the deposition of intrinsic hydrogenated microcrystalline silicon (μc-Si:H) films at very low temperatures by the Hot-Wire CVD technique is studied in this paper. The influence of the main technological 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 material at pressures lower than 1×10−2 mbar. Enhanced crystalline fractions over 95% have been obtained at very low temperatures (TS<200°C) by proper tuning of the hydrogen dilution. Moreover, this low substrate temperature has been shown to promote a decrease of the subgap absorption, which has been attributed to a low deep defect density related to the hydrogen passivation of dangling bonds in the grain boundaries.