Effect of Ar+ ion implantation on the nano-mechanical properties and microstructure of single crystal silicon

The effect of argon ion implantation on the nano-machanical properties of single crystal Si was examined making use of nano-indentation and nano-scratch tests. The morphologies of the scratched tracks of the unimplanted Si and that implanted at a moderate Ar+ fluence were observed on a scanning electron microscope, while the changes in the microstructure of the single crystal Si by Ar+ implantation were investigated on a transmittance electron microscope. It was found that the implantation of Si at a small or moderate fluence of Ar+ below 1 × 1015 ions/cm2 had little effect on the surface roughness and a minor effect on the surface nano-hardness. At the same time, the implantation of Si with Ar+ at a moderate fluence up to 1 × 1016 ions/cm2 led to a significant increase in the critical load. This was attributed to the desired changes in the microstructures of the single crystal Si by Ar+ implantation at a proper fluence. Namely, the Si surface implanted with Ar+ at a moderate fluence was composed of nano-sized polycrystalline Si uniformly distributed in amorphous Si matrix, which contributed to significantly increase the nano-scratch resistance and surface toughness of the single crystal silicon. It was suggested to implant the single crystal Si at an Ar+ fluence of 1 × 1016 ions/cm2 so as to acquire the optimized modification effect.