Grazing incidence impact of ions on an adatom-covered surface: Molecular-dynamics study of sputtering, surface-damage formation and ion-induced adatom mobility

Using molecular-dynamics simulation, we study the exemplary case of 5 keV Ar impact onto a Pt(1 1 1) surface at 83° incidence angle towards the surface normal. Under these conditions, on a flat terrace, the ions are specularly reflected, inducing neither damage nor sputtering of the surface. This situation changes drastically, if the surface is covered randomly with a coverage Θ of adatoms. For 0.1 < Θ < 0.5, average sputter yields and damage of up to a value of 5 and 9, respectively, are achieved. For coverages around Θ = 0.3-0.4, 50 adatoms are relocated on the average on the surface, affecting an area of around 1000 Å2. This ion-induced mobility promotes adatom clustering, which typically leads to a rim-like structure around the ion impact point.