Gas-phase synthesis and growth mechanism of SiC/SiO ₂ core-shell nanowires

A simple, non-catalytic synthetic route for SiC/SiO ₂ core-shell heterostructure nanowires (SiC/SiO ₂ 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 SiO ₂ 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.