Tailormade SiC-based nanocables by the control of the methane concentration

Two different nanocable (NC) structures (SiC/a-SiO2 and SiC/a-C), with a crystalline β-SiC inner core (8 and 25 nm in diameter), are synthesized by catalytic chemical vapour deposition at 950 deg. C from a mixture of H2-CH4 on Ni/Si substrates. At the same experimental conditions, on just increasing the methane concentration, a change in the external shell from a-SiO2 to an amorphous carbon layer is induced. As discussed, the type of nanostructure to be grown is controlled by the running growth mechanism changing from vapour-liquid-solid to solid-liquid-solid (SLS). In any case, the final growth mechanism depends on the availability of the reactive species during the formation process, which in turn is determined by the methane concentration in the gas mixture. In addition, a bottom-like model is proposed for the growth of the SiC/a-C NCs following the SLS mechanism.