Influence of Hydrogen Plasma Treatment Time to Si:H Layer Deposition Time Ratio on the Properties of Layer-by-Layer Deposited Hydrogenated Silicon (Si:H) Thin Films

摘要

Hydrogenated silicon (Si-H) thin films were deposited from a mixture of pure silane (SiH_4) and hydrogen (H_2) gases in a home-built plasma enhanced chemical vapour deposition (PECVD) system using the layer-by-layer (LBL) deposition technique. In the LBL process, the deposition was performed by periodically alternating the deposition of Si:H layer with the hydrogen treatment process of the growth surface. In this work, the effects of the H pasma treatment time to Si-H layer growth time ratio on the film properties were studied. The LBL deposited Si-H films studied in this work were deposited using different Si-H layer growth times ranging from 2 minutes to 7 minutes with the hydrogen plasma treatment time on the growth surface fixed at 3 minutes. Optical transmission spectroscopy, X-ray diffraction (XRD), micro-Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) measurements were done on these films to investigate the optical, structural and morphological properties of the films. The films deposited by this technique produced the highest deposition rate of 6.3 ks when the growth time of the Si-H layer was fixed at 5 minutes. These films were amorphous in structure and had large optical energy gaps irrespective of the Si-H layer deposition time. High concentration of cone-like structures was observed in the AFM images for the films deposited using the higher Si-H layer deposition times.