Hydrogen related crystallization in silicon carbide thin films

The present study reports on a detailed investigation on the transition from amorphous to nanocrystalline silicon carbide films grown by means of reactive radiofrequency magnetron sputtering process at low substrate temperatures Ts ranging from 200 °C to 500 °C. Fourier transform infrared spectroscopy (FTIR), optical transmission measurements and atomic force microscopy (AFM) images were used to study the structural and the optical properties of the films. The results clearly show that hydrogen atoms play a crucial role in the nanocrystal nucleation mechanism. The grown of the films is governed by the interactions between hydrogen atoms and SiC amorphous matrix. The FTIR analysis showed an abrupt structural transition from amorphous a-SiC:H to nc-SiC:H films occurred with increasing Ts from 250 °C to 300 °C. Upon increasing Ts, the extent of crystallization is substantial and reaches (70 ± 2) % for films deposited at 500 °C. In parallel, the total bonded hydrogen content decreases from 30 at.% to less than 6 at.%. The AFM observations confirm the structural changes in the films, and the average grain size reaches a value of about 60 nm.