Formation of tetrapod and multipod ZnO whiskers

ZnO tetrapod and multipod nanostructures were synthesized by vapor-phase transport method using the mixtures of ZnO (or ZnO:In2O3) and graphite powders as source materials. By controlling the growth condition, the tetrapod whiskers with homogeneous pillar, awl and inverse-awl shaped legs, and the multipods with the similar leg shapes were obtained. Combining X-ray diffraction pattern, scanning electron microscopy, and high-resolution transmission electron microscopy image of the products in initial and final growth stages, the growth process was investigated systematically. The influences of the source, growth temperature, and vapor pressure on the final morphology were discussed by considering the surface energy of nucleus and the kinetic energy of the incoming atoms.