Sputtering from ion-beam-roughened Cu surfaces

Abstract

A comprehensive theoretical and experimental study of sputtering from copper surfaces roughened by low-energy ${\mathrm{Ar}}^{+}$ ion bombardment is reported. The total sputtering yields of thermally deposited Cu samples bombarded by 400-eV and 800-eV ions at 0\ifmmode^\circ\else\textdegree\fi{}--70\ifmmode^\circ\else\textdegree\fi{} angles of incidence have been measured and compared with a numerical model we have developed. To compute sputtering yields from rough surfaces, an original approach has been introduced, which accounts for sputtering anisotropy and shadowing of material emitted at grazing angles. The approach is flexible with respect to surface morphology and can be applied with any submicron structures. To specify the morphology that develops on the Cu surface under low-energy ion bombardment, the surface of bombarded Cu samples has been investigated by scanning electron microscopy. The morphology has been found highly unstable, appearing with random roughening, inclined conelike structures, ripples, or almost flat surfaces, depending on the bombardment conditions. For the samples considered it is found that the angular dependency of the total sputtering yield is strongly affected by surface morphology, which varies with the angle of ion incidence and bombardment energy. Approximations for accounting for the surface roughness required to describe sputtering at particular energy and angular regimes are discussed.