Effect of hydrogen on the physical and mechanical properties of silicon carbide-derived carbon films

In this study, the effect of hydrogen on the structure and mechanical properties of carbon films produced by selective etching of monolithic SiC was examined. The process to produce carbon films from SiC (i.e., SiC-derived carbon, CDC) was carried out in a gas mixture of Cl2 and H2 at 1000 °C for 20 h. The Raman intensity ratio, ID/IG, where subscripts D and G refer to diamond and graphite, decreased as the hydrogen concentration in the gas mixture increased, indicating a decrease in the sp2 carbon cluster. XRD analysis also showed that the fraction of graphitization decreased as the hydrogen concentration increased. The addition of hydrogen that prevented the formation of graphite (sp2 bonding) also resulted in a reduction in the film thickness. The hardness and elastic modulus of the carbon films tended to decrease as the H2 content increased owing to the contribution from the C–H bond and the nano-size pore.