Investigation of the Hardness and Young's Modulus in Thin Near-Surface Layers of Silicon Carbide from the Si- and C-Faces by Nanoindentation

The results of hardness and Young's modulus study of near-surface layers of 4H-SiC hexagonal silicon carbide obtained by the modified Lely method from the C-face (000) and Si-face (0001) at shallow depths of the indenter are presented. It is shown that the differences in the elastic properties and hardness of SiC propagate from the surface into the crystal at a depth of about 60 nm. The Young's modulus at the C-face almost coincides with the Young's modulus of the bulk 4H-SiC sample (similar to 400 GPa), which is approximately 2.3 times higher than the Young's modulus at the Si-face at a depth of 0-35 nm (similar to 170 GPa). The hardness coefficient of SiC is on average about 1.5 times higher at the surface of the C-face (000) than at the Si-face (0001) at a depth of 0-60 nm. Since a new surface is formed upon deformation or destruction of the crystal (formation of cracks), based on the data obtained, it is concluded that the surface energy of the C-face is also about 1.5 times higher than the surface energy of the Si-face.