Thermal annealing effects on the optical properties of amorphous silicon carbide films deposited by pulsed laser ablation

摘要

Thermal annealing of amorphous SiC films deposited by pulsed laser ablation is performed at different temperature of 900-1050°C in vacuum condition. The structural and optical properties of the obtained films have been investigated by Micro-Raman scattering, UV-VIS transmission, and atomic force microscopy (AFM). It has been observed that the Raman bands related to SiC TO and LO modes appear and gradually shift to higher energy with increasing the annealing temperature, indicating that the crystallization of SiC occurs in the post-annealed films and their crystallinity increases. AFM results show that the post-annealed film is composed of compact nanoparticles and presents a rougher surface with respect to the as-deposited film. Optical band gaps deduced from UV-VIS transmission spectra are continuously increased from 1.90 eV for as deposited films to 2.45 eV of the annealed films at temperature of 1050°C. The formation of SiC nanocrystallines and the improvement of crystallinity can account for this blue-shift effect of the optical band gap.