Characterization and role of hydrogen in nc-Si:H

Abstract The effects of hydrogen on the properties of polycrystaline (nanometer sized) SiH films (nc-SiH) prepared by plasma enhanced chemical vapor deposition from SiH 4 diluted with H 2 have been studied. In the gas effusion from a sample, three effusion peaks of H 2 are found near 400°C, 500°C and 600°C. The origins of these peaks are assumed to be hydrogen effused from Si–H 2 and Si–H bonds in grain boundaries, and Si–H bonds in amorphous regions, respectively. From a deconvolution of the gas effusion data, the hydrogen density in the grain boundaries is found to decrease with increasing crystalline volume fraction, X c , while that in the amorphous regions is independent of X c . Based on the dependence of the amplitudes Si–H vibrational modes on X c and annealing temperature, the modes near 840 and 2100 cm −1 are related to hydrogen–silicon bonds in grain boundaries. The properties and role of hydrogen in nc-Si:H are discussed.