Molecular Dynamics Study of Alumina Nanoparticles' Effects on Silicon Bicrystal Amorphization at Varying Temperatures and External Shear Stresses

This study investigates the effects of alumina nanoparticles on the amorphization process of silicon bi-crystals using molecular dynamics simulations. The simulations, conducted with the LAMMPS package, model a bi-crystal system containing 1620 atoms within a 129×180×7.5 ų box, employing the TERSOFF potential for silicon and the Lennard-Jones potential for interactions between silicon and alumina nanoparticles. The simulation process consists of two stages: an equilibrium phase at temperatures ranging from 200 to 600 K for 1 ns, followed by an amorphization phase under external shear stresses from 1.55 to 2.50 GPa for another 1 ns. Key findings include the achievement of equilibrium after 1 ns at 300 K, with potential energy and mean atomic stress converging to -2.89 eV and 47.83 MPa, respectively. Amorphization is induced by shear stress, with the amorphization length increasing from 5.26 Å at 300 K and 1.55 GPa to 5.98 Å at 600 K and 2.50 GPa. Alumina nanoparticles serve as nucleation sites, significantly promoting the amorphization process by enhancing dislocation density and structural disorder. These results indicate that nanoparticles provide a more effective means of controlling amorphization compared to adjustments in temperature and shear stress, with potential applications in semiconductor device fabrication and solar cell manufacturing. The presence of nano-alumina slows the progression of the amorphization process. Consequently, under identical conditions—including temperature, applied external shear stress, and time—the rate of dislocation formation decreases, resulting in approximately 20% fewer dislocations overall. Additionally, the yielding stress threshold of a single crystal has increased from 8.2 to 12.8 GPa, indicating a significant enhancement in the material's resistance to deformation under applied stress.