STEP FORMATION ON THE ION-BOMBARDED AG(100) SURFACE STUDIED BY LEED AND MONTE-CARLO SIMULATIONS

The development of the morphology of an Ag(100) single-crystal surface bombarded with 600 eV Ar+ ions at 170 K and at room temperature is studied by spot profile analysis of LEED. A temperature-dependent saturation of the step density is observed and a distinct smoothing of the surface after bombardment occurs already at room temperature. Under out-of-phase condition the LEED spots show a fourfold shape that differs in orientation at both temperatures. Monte Carlo simulations of the atom removal including thermal surface diffusion reveal at 170 K the formation of <100> and <110> step edges with equal probability, whereas at room temperature rearrangement processes at the steps lead to the preferential formation of the close-packed <110> edges. The intensity distribution under out-of-phase condition calculated from the Monte Carlo snap shots exhibits the same temperature dependence of the spot shapes as observed experimentally. The interlayer mass transport occurring during annealing at room temperature is found to be based on jumps running downward the <100> step edges.