Material Deformation and Damage Mechanism Based on In-Situ Plasma-Assisted Nanoscratch Test of Single Crystal Silicon

Abstract Due to the high hardness and low fracture toughness of the single crystal silicon (SCS), it is highly susceptible to microscopic cracks and subsurface damage during processing. In this paper, we propose to adjust the mechanical properties of SCS by cold plasma jet, and systematically investigate the influences of the plasma on material deformation and damage mechanisms by nanoscratch tests. The results indicate that the plasma can increase the critical normal force for the plastic-brittle (P-B) conversion of SCS. Compared with the ordinary nanoscratch test, the critical force for P-B conversion of plasma-assisted scratching at 1 μm/s can increase from 43.6 to 66.4 mN. Increasing the scratching speed under ordinary conditions can enhance the plastic deformability of SCS to some extent, but its effect is not as effective as that of plasma; in addition, the increased scratching speed causes the shear bands (SBs) to lack time to propagate, so the quantity of SBs under plasma-assisted scratching at 10 μm/s is reduced compared to 1 μm/s. From subsurface damage topographies, the highly localized amorphous SBs cause the generation of subsurface cracks. The cold plasma can alleviate cracks on the scratched subsurface of SCS by introducing multiple SBs and stacking faults. This paper may provide a novel strategy for high-efficiency and low-damage ultra-precision machining of hard and brittle materials.