Hexagonal geometric patterns formed by radial pore growth of InP based on Voronoi tessellation.

To fabricate ordered geometric patterns consisting of InP nanoporous structures, a photoresist mask with periodic opening arrays was prepared by sphere photolithography. The diameter and interval of the openings of the photoresist mask could be controlled independently by adjusting the diameter of silica spheres used as a lens and the exposure time. Through this resist mask with a two-dimensional (2D) hexagonal array of openings, the pore growth of InP during anodic etching was investigated. The isolated openings could act as initiation sites for the radial growth of pores, resulting in the formation of hexagonal geometric patterns based on Voronoi tessellation in 2D space. With further anodic etching, inside the substrate, the growth direction of the pores changed from radial to perpendicular relative to the substrate. Moreover, by removing domains consisting of nanopores by anisotropic chemical etching, the fabrication of InP microhole arrays with circular and triangular cross sections was also achieved.