Wetting regime of semiconductor nanowhisker growth: Stability and shape of catalyst droplet

A new, wetting regime of semiconductor nanowhisker (NW) growth according to the vapor-liquid-solid (VLS) mechanism, whereby a catalyst drop spreads about the NW top, has been theoretically studied. The NW growth in a wetting regime can take place provided that the surface energy of the drop is sufficiently low, which is possible, e.g., for the autocatalytic growth of GaAs nanowhiskers on Ga drops. The shape of the drop in a wetting configuration has been determined using conditions of the mechanical balance of surface forces and minimum of the surface energy functional. It is established that the shape of a spherical segment on the NW top, which is matched to the unduloid surrounding the NW side surface. The influence of the drop configuration on the crystalline structure of autocatalytically grown GaAs nanowhiskers is considered. It is shown that the NW growth in a non-wetting regime is typical of small initial drop volumes, whereas a wetting regime is characteristic of sufficiently large initial drops.