Differences between the nc-Si:H thin films deposited by RF-sputtering and PECVD

Nanocrystalline silicon thin films were deposited by radio frequency(RF) sputtering and by PECVD separately with the processing parameters varied. A combination of X-ray diffraction (XRD), ellipsometry and Raman measurements were used to characterize the films. The optical band gaps(E_g ^opt) were derived from Tauc plots, and the result showed that the films prepared by RF-sputtering has a wider band-gap compared with the film deposited by PECVD, and suitable for the solar cell window layer. A investigation of the differences in Raman shift and the crystallization ratio(Xc) between the two kinds of films were also carried out. The XRD results shown that the film deposited by the radio frequency(RF) sputtering has a preferred orientation in (201) and this preferred diffraction orientation corresponds to tetragon microstructure, which has a wider band-gap compared with the silicon films deposited by PECVD.