Impact of dilution gases on structure, properties and growth of hydrogenated nanocrystalline silicon (nc-Si:H) prepared by HW-CVD method

Abstract

In this work we present a detailed structural, optical and electrical characterization of hydrogenated nanocrystalline silicon (nc-Si:H) thin films grown by hot wire chemical vapor deposition (HW-CVD) as a function of hydrogen (H 2), argon (Ar) and helium (He) dilution of silane. A variety of analysis techniques such as Raman spectroscopy (RS), x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, UV-Visible spectroscopy and conductivity measurements were used to characterize the grown films. We observed that these properties are greatly influenced by dilution of silane with H 2 , Ar and He. Characterization of these films by Raman spectroscopy and low angle x-ray diffraction revealed that the increase in H 2 and Ar dilution of silane endorses the growth of crystallinity in the films whereas increase in He dilution of silane deteriorates the film properties. An attempt has been made to explain the fundamental differences in nanocrystallization growth mechanism by addition of H 2 , Ar and He in silane.