Influence of the anisotropy of single crystal 4H-SiC on contact responses during nanoindentation and microscratch

Abstract

The effect of anisotropy, which is crucial for manufacturing single crystals, was investigated in this study by performing nanoindentation experiments on the Si/C plane of single crystal 4H-SiC with the edge of Berkovich indenter toward with two different crystal orientations of \([11\overline{2} 0]\)/\([1\overline{1} 00]\). On the Si plane, when the edge was toward crystal orientation \([11\overline{2} 0]\)/\([1\overline{1} 00]\), the indentation hardness is 39.37/39.77 GPa, the elastic modulus is 528.16/513.88 GPa, and the fracture toughness is 3.286/2.609 MPa·m^1/2. On the C plane, when the edge was toward crystal orientation \([11\overline{2} 0]\)/\([1\overline{1} 00]\), the indentation hardness is 43.66/41.91 GPa, the elastic modulus is 522.24/546.54 GPa and the fracture toughness is 2.826/2.705 MPa·m^1/2. At the same time, the Vickers hardness crack induction method was used to calculate the fracture toughness, regardless of the Si or C plane, the fracture toughness value of the crystal orientation \([11\overline{2} 0]\) is generally greater than that \([1\overline{1} 00]\). Molecular dynamics (MD) indentation simulations were carried out with the indenter edge facing different crystal directions of the Si plane. There is obvious anisotropy in the depth of the amorphous atomic layer, the number and proportion of dislocation nucleation, and the shear strain expansion. Although microscratch experiments combined with the analysis of scratch variables and the optical topography of scratches, it is concluded that the scratch deformation damage towards the crystal orientation \([1\overline{1} 00]\) is smaller. This study can provide theoretical guidance for the ultra-precision machining of the anisotropy of 4H-SiC crystal structure.