The structural symmetry of nanoholes upon droplet epitaxy

Nanoholes obtained by droplet epitaxy has been intensively investigated as an important material platform for the fabrication of nanodevices due to their unique topology. However, the final fabricated nanoholes are very difficult to achieve a highly symmetric circular structure, and usually have two or four gaps in the sidewall of the holes. Here we have presented a developed model to inquire into the reasons for the formation of the gaps at the periphery of nanoholes and discuss how to improve the structural symmetry of the nanoholes. It is found that the anisotropic interface diffusion of As atoms decomposed by substrate can result in the formation of the gaps. In order to improve the symmetry of final nanostructures, we can minimize the interval time between deposition of Ga droplets and open operation of As flux, and set up a multistep growth procedure by changing the intensity of As flux or growth temperature.