Fabrication of Si-nanowires controlled by spontaneously formed nanoholes on annealed Au thin films

Si nanowires (Si-NWs) were fabricated by a simple process that consists of deposition of Au thin films, annealing of the Au films to form porous structure and Si wet-etching using the kinetically appearing porous Au films as a template. The deformation behavior of the Au thin films was investigated by scanning electron microscopy and atomic force microscopy. The nanohole diameter and density of the Au films can be controlled by selecting Au film thickness, annealing temperature and annealing time. The formation mechanism of these porous Au films can be explained by a model that consists of nanohole formation at the grain boundaries of the Au films and ridge formation by Au atom diffusion to the hole periphery. The ridge structure suppresses further deformation of the Au films and keeps the nanohole structure kinetically stable. When a thermal energy larger than the activation energy to destroy the ridge structure is supplied, it transforms to the island structure.