Anisotropy of the crater function of the Cu surface under Ar bombardment

Using molecular-dynamics simulation we calculate the crater function - i.e., the surface height profile averaged over many ion impacts on a virgin surface - for the case of a single-crystalline surface. The special case of 500 eV Ar impact into a Cu surface is considered, and 3 different surface orientations - (1 0 0), (1 1 0) and (1 1 1) - are calculated. We find that the crater function reflects the anisotropy of the surface. In particular, the crater rim follows the adatom angular emission distribution; its symmetry corresponds to the well-known angular distribution of sputtered atoms, the so-called Wehner spots. Erosive (sputtering) and relocative (adatom formation) contributions to the crater pit follow the energetics of the necessary bond breaks and are in a ratio of ∼1:2.5.