Hydrogenated nanocrystalline silicon thin films prepared by hot-wire method with varied process pressure

Hydrogenated nanocrystalline silicon films were prepared by hot-wire method at low substrate temperature (200°) without hydrogen dilution of silane (sih 4). a variety of techniques,including raman spectroscopy,low angle x-ray diffraction (xrd),fourier transform infrared (ftir) spectroscopy,atomic force microscopy (afm),and uv-visible (uv-vis) spectroscopy,were used to characterize these films for structural and optical properties. films are grown at reasonably high deposition rates (≥15å/s),which are very much appreciated for the fabrication of cost effective devices. different crystalline fractions (from 2.5 to 63) and crystallite size (3.6-6.0nm) can be achieved by controlling the process pressure. it is observed that with increase in process pressure,the hydrogen bonding in the films shifts from sih to sih 2 and (si-h 2) n complexes. the band gaps of the films are found in the range 1.83-2.11ev,whereas the hydrogen content remains ≤9 at. over the entire range of process pressure studied. the ease of depositing films with tunable band gap is useful for fabrication of tandem solar cells. a correlation between structural and optical properties has been found and discussed in detail. © 2011 v. s. waman et al.