Y. Yan, Y. Wang, P. Zhou, N. Huang and D. Guo
Precision Engineering 56, 506 (2019)
Knowledge about the removal mechanism at the nanometer scale is essential for eliminating the negative effects of surface defects and subsurface damages of silicon finishing with the ultra-precision machine. It is always studied by the scratching tests and how to distinguish the characteristics of scratch is of great importance to further analysis of material removal mechanism. In this study, the scattering-type scanning near-field optical microscopy (s-SNOM) was employed as a direct and non-destructive method to characterize the scratch generated by single-point diamond scratching. The near-field amplitude obtained by s-SNOM was in direct proportion to the free-carrier concentration that represents the subsurface dislocation of silicon, and the plastic regime of the scratch could be distinguished. Furthermore, s-SNOM could tell the difference between plastic pileups and burrs, and the microstructures at the subsurface of the scratch can be detected as well. These characteristics are critical to investigate the material removal mechanisms in ultra-precision machining but the AFM and SEM could just observe the surface morphology instead of telling the difference between various regimes. sSNOM provided possibilities for nanoscale material characterization and could become a tool for subsurface damages observation of ultra-precision machined materials.