Tensile behavior and mechanical properties of single-crystal AlN under uniaxial tension loading

Abstract In order to investigate the microstructural response, mechanical characteristics, and fracture mechanism of aluminum nitride (AlN) during the tensile process, molecular dynamics simulation is used to study the effects of crystal direction, strain rate, environmental temperature, and hole defects on atomic movement trajectories, anisotropic characteristics, crack fracture behavior, mechanical response, and energy at the atomic scale. The results indicate that the [100] crystal direction of AlN has the highest elastic modulus and tensile strength; the [010] crystal direction has the weakest tensile strength and ductility; and the [001] crystal direction exhibits both higher tensile strength and optimal ductility. When the strain rate is 0.001 ps −1 , the tensile strength is highest; when the strain rate is 0.0005 ps −1 , the number of Al-N bond fractures is lowest, resulting in the most stable crack fracture surface structure. In a high-temperature environment, the intermolecular bonding forces within the material weaken, making it easier for grain boundaries to move and slip, resulting in a decrease in tensile strength and an accelerated crack propagation rate. Under the condition of hole defects, the variation trend of potential energy and tensile strength is that the [001] crystal direction has the largest decline, the [010] crystal direction follows, and the [100] crystal direction has the smallest. Increasing the hole size causes more AlN lattice to be destroyed, and the stress distribution inside the material is less uniform, and it is easier to fracture under lower strain. This study systematically analyzes the tensile deformation behavior of AlN at the atomic scale, which can help optimize the bonding strength at the thin film/substrate interface and prevent cracking or delamination caused by thermal mismatch and crystal defects, thereby improving the reliability of high-performance AlN devices.