Microstructures of microcrystalline silicon thin films prepared by hot wire chemical vapor deposition

Undoped hydrogenated microcrystalline silicon (mu c-Si:H) thin films were p repared at low temperature by hot wire chemical vapor deposition (HWCVD). M icrostructures of the mu c-Si:H films with different H-2/SiH4 ratios and de position pressures have been characterized by infrared spectroscopy X-ray d iffraction (XRD), Raman scattering, Fourier transform (FTIR), cross-section al transmission electron microscopy (TEM) and small angle X-ray scattering (SAX). The crystallization of silicon thin film was enhanced by hydrogen di lution and deposition pressure. The TEM result shows the columnar growth of mu c-Si:H thin films. An initial microcrystalline Si layer on the glass su bstrate, instead of the amorphous layer commonly observed in plasma enhance d chemical vapor deposition (PECVD), was observed from TEM and backside inc ident Raman spectra. The SAXS data indicate an enhancement of the mass dens ity of mu c-Si:H films by hydrogen dilution. Finally, combining the FTIR da ta with the SAXS experiment suggests that the Si--H bonds in mu c-Si:H and in polycrystalline Si thin films are located at the grain boundaries. (C) 2 000 Elsevier Science S.A. All rights reserved.