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 nanosized polycrystalline Si uniformly distributed in amorphous Si matrix, which contributed to significantly increase the nanoscratch 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.