Selective growth of Co islands on ion beam induced nucleation centers in a native SiO_2 film

摘要

We present a straightforward method for fabrication of patterns of metallic nanostructures. The focused ion beam (FIB) lithography has been used to locally modify a native SiO_2 layer on a silicon substrate. On the modified areas preferential nucleation of cobalt islands is observed. The cobalt islands formed upon deposition at 400-430 ℃ combined with an intermediate annealing at 550 ℃ have a uniform size distribution and their size can be controlled by the distance between the nucleation sites and the amount of deposited material. It is proposed that the island formation at patterned sites is due to reduced surface diffusion of Co atoms in the vicinity of FIB modified areas. The intermediate annealing improves the island morphology since the kinetic diffusion limits are lowered and system reconfigures toward its equilibrium state.