Atomic Analysis of Contact-induced Subsurface Damage Behavior of Single Crystal SiC Based on Molecular Simulation

It is helpful to understand the microstructure evolution characteristics and mechanical properties of monocrystalline SiC semiconductor devices during contact from the perspective of atomic scale to understand the microscopic mechanism of subsurface damage behavior and phase transformation. Based on the Vashishta potential function of molecular dynamics, the microscopic evolution characteristics of the nano-indentation induced dislocation rings, the amount of phase transformation and the contact mechanical properties of the corresponding monocrystalline SiC surface were studied, and the effect of extreme service temperature on the subsurface damage behavior and the contact mechanical properties were analyzed. The results show that the plastic deformation of SiC subsurface damage is mainly caused by dislocation nucleation, dislocation accumulation and dislocation slip, whilst the dislocation ring goes through four evolution stages during contact, i.e., dislocation nucleation, dislocation ring growth, dislocation ring reproduction and dislocation ring brittle break. Besides, with the increasing temperature, the maximum bearing capacity, hardness, Young's modulus and contact stiffness curves of silicon carbide materials show a parabolic trend of decline. The main reason is that the higher the temperature is, the SiC lattice is easy to get rid of the bondage of atomic bond energy, resulting in lattice defects, and easy to breed dislocation, which result in the enrichment of stress concentration on subsurface of materials at lastly. As a result, the mechanical properties of SiC materials are greatly reduced while being contacted. In addition, the subsurface stress concentration is also the fundamental reason for the phase transformation from cubic to sphalerite for SiC materials. With the increase of temperature, the amount of phase transformation increases. The dynamic contact plastic deformation and micro-structure evolution of SiC in semiconductor devices under loading, and the phase transformation are significantly dependent on the operating temperature. The rising temperature related change of crystal lattice and the generation of random rough spots on the surface are the main causes of contact adhesion. This study may provide a deeper understand on contact mechanical properties and sub-surface damage behavior at extreme service temperatures, and will also enrich the understanding of the contact failure mechanism of nano silicon carbide. © 2023 Chinese Journal of Materials Research. All rights reserved.