On the deformation mechanism of SiC under nano-scratching: An experimental investigation

SiC is an important semiconductor but is difficult to machine due to its high hardness and low fracture toughness. The deformation mechanisms of SiC subjected to single-point cutting is so far unclear. This paper aims to clarify such mechanisms by carrying out experimental investigations at similar length and load scales to those based on molecular dynamics. To this end, nano-scratching tests were conducted on AFM. Diamond AFM tips of the radius of 10 nm and 60 nm were used as the single-point nano-scratching tool on the surfaces of 4H-SiC and 6H-SiC single crystals with oxide amorphous layer. The nano-grooves were then examined under AFM and SEM, and the damages in the cross-sectional subsurfaces were analyzed by HRTEM. The investigation revealed that under the nano-scratching load less than 20 mu N and nano-grooving depth below 10 nm, which are consistent with the conditions used in molecular dynamics analyses, the subsurface deformation was mainly caused by amorphous phase transformation. Dislocations were rarely found and no crack emerged. This study then identified that under nano-scratching, the main mechanism of material removal of a single crystalline SiC is via amorphous phase transformation.