Structural and optical properties of the a-Si:H thin films irradiated by high energetic electron beams

Abstract

Hydrogenated amorphous silicon (a-Si:H) films deposited on quartz substrate by radio-frequency plasma enhanced chemical vapour deposition were irradiated by an high energetic electron beam source from an electronic gun device. The effects of the high energetic electron beam current density (0.32–0.81 mA/mm2) irradiations on the structural and optical properties of the nc-Si:H thin films have been investigated by atomic force microscopy (AFM), Fourier transform infrared spectroscopy, Raman scattering spectroscopy, X-ray diffraction (XRD) spectroscopy, ultraviolet and visible spectroscopy. The AFM analysis showed increase in the root-mean-square roughness and increase in average grain size. Raman and XRD measurements revealed increasing electron beam current favored enhancement of crystallinity and enlargement of crystallites. The optical band gap of the films is broaden, which can be explained in terms of the reduced hydrogen content and phonon confinement effect. The increasing trend of the B with the variation of electron beam current reveals a more ordered film structure disorder. From the results, it was interesting to found that the optical constants showed a good correlation with the crystallinity within the variation of electron beam current density. The variation of the optical energy gap based on structure disorder and the quantum confinement effect is also discussed.