Morphological engineering of self-assembled nanostructures at nanoscale on faceted GaAs nanowires by droplet epitaxy.

Fabrication of advanced artificial nanomaterials is a long-term pursuit to fulfill the promises of nanomaterials and it is of utter importance to manipulate materials at nanoscale to meet urgent demands of nanostructures with designed properties. Herein, we demonstrate the morphological tailoring of self-assembled nanostructures on faceted GaAs nanowires (NWs). The NWs are deposited on different kinds of substrates. Triangular and hexagonal prism morphologies are obtained, and their corresponding {110} sidewalls act as platforms for the nucleation of gallium droplets (GDs). We demonstrate that the morphologies of the nanostructures depend not only on the annealing conditions but also on the morphologies of the NWs' sidewalls. Here, we achieve morphological engineering in the form of novel quantum dots (QDs), 'square' quantum rings (QRs), 'rectangular' QRs, 3D QRs, crescent-shaped QRs, and nano-antidots. The evolution mechanisms for the peculiar morphologies of both NWs and nanostructures are modeled and discussed in detail. This work shows the potential of combining nano-structural engineering with NWs to achieve multifunctional properties and applications.