Mechanism For Anisotropic Ejection Of Atoms From Fcc (100) Metal Surface By Low-Energy Argon Ion Bombardment: Molecular Dynamics Simulation

In order to thoroughly clarify the formation mechanism of "Wehner spots" during the low-energy sputtering of fcc (100) surface, molecular dynamics (MD) method was employed to investigate the sputtering of Cu (100) surface by 500 eV argon ion bombardment. Simulation program monitored the emission trajectories and velocities of sputtered atoms as well as the forces acting on them. Simulation results revealed that the preferential ejection of sputtered atoms along close-packed directions, which caused the formation of "Wehner spots", resulted mainly from the regular interaction between sputtered atoms and their neighbor atoms. The formation mechanism of "Wehner spots" is that sputtered atom is first horizontally focused and then undergoes a ski-jump takeoff along close-packed direction. The generality of this mechanism was further verified by supplementary molecular dynamics simulations. Furthermore, this investigation demonstrated that local environment surrounding sputtered atom rather than simple collision processes transferring initial recoil energy to sputtered atom dominated the anisotropic sputtering of fcc (100) surface in low energy regime.