Application of Radio Frequency Glow Discharge Sputtering for Nanoindentation Sample Preparation

The applicability of radio frequency glow discharge (rf-GD) sputtering to the surface finishing of nanoindentation specimens was examined for pure Al, Cu, and Ni. Comparisons were made between specimens that had been subjected to the following surface finishing: (1) rf-GD sputtering, (2) electropolishing, and (3) mechanical polishing with 0.25 µm of diamond suspension. It was suggested from the nanoindentation behavior and the quality of electron backscattered diffraction patterns that residual damage on the surface of the rf-GD sputtered samples was as small as that of electropolished samples, while some damages remained on the surface of the mechanically polished samples. The areal roughness within a 1-μm square of the rf-GD sputtered surface was comparable to that of the mechanically polished surface and slightly larger than that of the electropolished surface. Nonetheless, the difference of the roughness within the range of this study has no practical impact upon nanohardness and elastic modulus evaluation. Pop-in events occurred in the electropolished and rf-GD sputtered specimens, but not in the mechanically polished samples. The critical load for pop-in to occur was slightly smaller in rf-GD sputtered sample than in electropolished samples.