Aligned heterostructures of single-crystalline tin nanowires encapsulated in amorphous carbon nanotubes

High-density heterostructures of amorphous carbon nanotubes encapsulated single-crystalline tin nanowires (a-CNT-Sn) have successfully been synthesized by using the simple thermal evaporation of solid tin powder (Sn) and introduction of ethylene gas (C2H4). A commercially widely used porous carbon paper, consisting of micrographitic fibers, was employed as growing substrate. The morphology, composition, and structure of the synthesized nano-heterostructures were examined using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) analysis. It was found that the resultant heterostructures are uniformly distributed on graphitic fibers and that these well-defined tin (Sn) nanowires, up to 10 mu m in length, are completely covered with amorphous carbon walls of about 30 nm thickness. The hollow features at the tips of such heterostructures were revealed. A growth mechanism has been proposed to explain the growth processes for such novel heterostructures. The synthesis method reported here can be employed to fabricate oriented nanotube arrays filled with other nanowires on a variety of substrates at large scale.