Evolution of Catalyst Droplets during VLS Growth and Cooling Process: A Case of Ge/ZnO Nanomatchsticks

Using Ge sphere-capped ZnO nanowires as a model system, we investigate the evolution of catalyst droplets and their influence on nanowire growth in the processes including vapor-liquid-solid (VLS) growth and cooling processes. The diameter ratios between Ge particle and ZnO nanowire have approximately a normal distribution. The atomic ratio of Ge/Zn in the particle during the growing process is found to deviate enormously front the eutectic point in the Ge-Zn binary phase of diagram, indicating tertiary phase diagram has to be used. Slow cooling allows the elements separation and crystallization of Ge-Zn-O droplets and continuous growth of the nanowire at the nanowire/catalyst sphere interface. The present studies largely extend the understanding of the VLS mechanism.