Computer simulations on collision-sequence mechanisms: Bombardment of single-crystalline Cu(100) by Ar ions.

Abstract

The development of collision-cascade anisotropies and the collision-sequence mechanisms in single-crystalline Cu are studied employing the binary-collision lattice-simulation code cosipo and the distributions of the recoil vector fluxes. The vector fluxes are directly related to other statistical distribution functions of recoils and to the angular distributions of sputtered particles. Single-crystal Cu(100) is bombarded with normally incident 5-keV Ar ions. In addition to depth resolution of the recoil vector fluxes, the evolution of anisotropies is studied as a function of energy. The effect of various types of collision sequences on the fluxes may be treated separately. The collision cascade is found to be highly anisotropic at different depths and energies of recoils, and it is dominated by focusing along the 〈110〉 directions. The development of the collision cascade is entirely governed by crystal structure. A diversity of mechanisms responsible for creating the chains exists. The contributions of various collision chain mechanisms to recoil flux distributions and observed spot patterns are discussed. Thermal vibrations shorten the collision sequences and decrease the contribution of chains to the flux distributions, except in the case of defocused chains. Their fraction increases when thermal vibrations are included.