RESUMEN
Here, we present a two-step annealing procedure to imprint nanofeatures on SiO2 starting from metallic microfeatures. The first annealing transforms the microfeatures into gold nanoparticles and the second imprints these nanoparticles into the SiO2 layer with nanometric control. The resulting nanohole arrays show a high ensemble uniformity. As a potential application, the nanohole mask is used as a selective mask for the Ga self-assisted growth of GaAs nanowires (NWs). Thus, for the first time, a successful implementation of nano-self-imprinting that links high-throughput microlithography with bottom-up NW growth is shown. The beneficial hole morphology of the SiO2 mask promotes high Ga droplet contact angles with the silicon substrate and the formation of single droplets in the mask holes. This droplet predeposition configuration enables a high vertical yield of NWs. Thus, this article describes a new protocol to grow NW devices that combines simultaneously nanosized holes and parallel processing.
RESUMEN
III-V semiconductor nanowires deterministically placed on top of silicon electronic platform would open many avenues in silicon-based photonics, quantum technologies and energy harvesting. For this to become a reality, gold-free site-selected growth is necessary. Here, we propose a mechanism which gives a clear route for maximizing the nanowire yield in the self-catalyzed growth fashion. It is widely accepted that growth of nanowires occurs on a layer-by-layer basis, starting at the triple-phase line. Contrary to common understanding, we find that vertical growth of nanowires starts at the oxide-substrate line interface, forming a ring-like structure several layers thick. This is granted by optimizing the diameter/height aspect ratio and cylindrical symmetry of holes, which impacts the diffusion flux of the group V element through the well-positioned group III droplet. This work provides clear grounds for realistic integration of III-Vs on silicon and for the organized growth of nanowires in other material systems.