SIMULATION OF CLUSTER IMPACTS ON SILICON SURFACE

A new hybrid model, combining Molecular Dynamics (MD) with continuum m echanics and thermodynamics, has been developed for studying collision s of energetic particles with a solid surface. MD describes interactio n of atoms in the central impact zone characterized by energetic atomi c collisions and non-equilibrium states of matter while the continuum model is applied to a much larger volume outside. Appropriate boundary conditions at the interface of the two regions prevent the appearance of unphysical shock wave reflections. The hybrid model is very effici ent in computations as it reduces the number of the system's degrees o f freedom by minimizing the size of the central MD zone. The model was applied to collisions of a few keV Ar clusters containing approximate ly 100 atoms with Si(100) surface. The results show that cluster impac ts create craters and local melting and that a number of displaced sur face atoms have large lateral velocities. The latter may explain the e xperimentally observed surface smoothing by cluster bombardment.