Hydrogen effect on structural and optical properties of in-situ fabricated nc-Si:H prepared by facing targets sputtering

We report high-quality hydrogenated nanocrystalline silicon (nc-Si:H) thin films were prepared by facing targets sputtering (FTS) in the environment of Ar and H₂ mixture gases. By increasing hydrogen dilution (R_H) of FTS deposition, the structural evolution of as-fabricated Si-based films was observed. Fourier infrared spectroscopy (FTIR) shows that decrease in bonded hydrogen (C_H) concentration, especially that of (Si-H₂)_n with increasing R_H, indicating that the H etching effect increased atomic density of these films, thus improving film quality. With the R_H increased, the Raman spectra show that the morphological transition from amorphous to crystalline states. We further reveal correlations between the degree of structural order in the amorphous network and the R_H by calculating experimental data from the Raman measurements. Moreover, as-fabricated nc-Si:H films show large bandgap and narrow band tail states with increasing R_H, which allows potential applications in the window passivation layer for HIT solar cells and Si-based charge-coupled devices (CCD). This work offers a novel route to fabricate high-quality nc-Si:H films for optoelectronic applications.