Abstract
Abstract Using the plating of galvanic displacement, nanometer-sized noble metal clusters can be grown on silicon surface. Although intensive applications and researches were focused on the issue, the detailed mechanism of galvanic displacement is not completely understood. We use atomic force microscopy to study the adhesion of reduced metal on silicon substrates, effects of plating solutions and hydrophilicity of silicon surface on plating, and vacuum annealing effect on aggregation of deposited metal clusters. We found that the adhesion of gold particles reduced in solution without HF is very weak. Being rinsed by de-ionized water, such gold particles can be depleted on the silicon surface. In contrast, the deposited gold particles have stronger adhesion and the reduction reaction is easier to occur when a HF-contained solution is used. Reduction of metal ions is easier to occur on a hydrophilic OH-Si surface than on a hydrophilic H-Si surface. This may be ascribed to the hydrophilicity of OH-Si surface and its higher reactivity of redox reaction on Si. The methanol-contained solution is also found to enhance the reduction of metal ion. Improvement the reactivity of H-Si by methanol is likely the cause. Unlike PVD, when the reduced gold clusters is annealed to 500~600∘in vacuum, aggregation of clusters does not happen. We can achieve selective deposition of metal on Si surface by using Si3N4 and SiO2 as mask. Finally, we use galvanic displacement method to reduce Ni on Si surface.