Influence of annealing conditions on the characteristics of nanoholes formed by focused ion beams on the GaAs(111) surface

In this paper, we study the effect of annealing of GaAs(111) substrates under various conditions on the morphological characteristics of nanoholes formed by focused ion beams. In the absence of annealing and when annealing in  the absence of the arsenic flux, the depth and lateral size of nanoholes increase with the number of ion beam passes. In the case of annealing of the substrates in the arsenic flux, the dependences of the hole depth and lateral size  on the number of beam passes is non-monotonic, which is attributed to the competition of the processes of surface etching by gallium droplets during thermal oxide removal and droplet crystallization in the arsenic flux. We demonstrate technological conditions enabling formation of highly symmetric nanoholes in the form of triangular pyramids.