Solid-phase crystallization of high growth rate amorphous silicon films deposited by gas-jet electron beam plasma CVD method

Abstract

Solid phase crystallization of amorphous silicon films (a-Si:H) deposited by gas-jet electron beam plasma chemical vapor deposition method and annealed at 700 °C in vacuum has been investigated. This method provides high deposition rates (up to 2.3 nm/s) of a-Si:H thin films in a standard vacuum chamber. The effects of varying the substrate temperature from 190 to 415 °C on the structural and optical properties of the as-deposited amorphous films and postannealed nanocrystalline films have been investigated. The crystallite size was determined by X-ray diffraction (about 5–8 nm) and agrees with that obtained from Raman scattering. The estimated degree of crystallinity was 45%–59%. Optical transmission spectra were recorded to investigate the optical properties and thickness of the silicon thin films. The refractive index and optical band gap data was obtained for both as-deposited amorphous and post-annealed nanocrystalline silicon. The behavior of the refractive index of nanocrystalline silicon depending on the substrate temperature is correlated with the crystalline volume fraction. a-Si:H films obtained at low temperatures have larger crystallite size and better crystallinity after annealing.