Gas-phase synthesis and growth mechanism of SiC/SiO2 core-shell nanowires

A simple, non-catalytic synthetic route for SiC/SiO2 core-shell heterostructure nanowires (SiC/SiO2 NWs) is presented, which involves establishment of separate regions for source gas decomposition and NW deposition in a chemical vapour deposition tube reactor. The O-2 flow rate controlled the NW diameter, which could be varied in the range 30-490 nm, and also allowed adjustment of the core-shell diameter ratio. The NW length directly increased with deposition time. The SiC core possessed a smooth spiral structure that grew in the [111] direction via a screw dislocation mechanism. The factors determining the core-shell diameter ratio, predominant species in each temperature region, and sequence of SiO2 shell formation were identified by thermodynamic calculations. We expect this new simple synthetic route to be useful in producing other heterostructure materials with compositional ordering.