Sputtering of stepped Cu surfaces by 3 keV Ar projectiles with glancing angles of incidence

The sputtering characteristics of Cu crystal targets with stepped surfaces have been examined with classical dynamics computer simulations. The predicted yields, angular distributions, statistical properties and spatial origins of sputtered atoms are reported. The three targets investigated were: a Cu(1 0 0) surface with a monatomic step, denoted Cu(1 0 0)-(S); the Cu(29, 1, 1) surface; and the Cu(20, 1, 1) surface. A 3 keV Ar projectile with a glancing angle of incidence ( ϕ=5°) was employed. The surface structures of the targets consist of (1 0 0) terraces separated by monatomic (1 1 1) steps. For the Cu(29, 1, 1) and Cu(20, 1, 1) targets, the spatial distributions of sputtered atom lattice sites display a bimodal character. The peaks of the distributions are localised in the vicinity of the (1 1 1) steps which lie behind the primary zone of projectile impact. This pattern of sputtering can be understood with the help of a two-dimensional description of the projectile–target interaction. Projectile–surface atom close encounters are possible when projectiles undergo direct collisions with atoms at the leading terrace edge on their approach to the surface, or when projectiles reflected from the primary impact zone are focussed onto edge atoms in the adjacent terrace. For the Cu(1 0 0)-(S) target, only the first mechanism is feasible.