Oblique incidence deposition of Cu/Cu(001): Enhanced roughness and ripple formation

Abstract

Polar angle of incidence, substrate temperature, and atom flux are of key importance to the self-organisation process on a substrate surface during oblique incidence deposition. The substantial influence of these parameters in homoepitaxial growth on Cu(001) is studied using scanning tunneling microscopy, high-resolution low-energy electron diffraction, and extensive growth simulation. The quantitative simulations reproduce the experimentally observed phenomena in great detail provided the steering effect is incorporated and accurate barriers for interlayer transport are used. Both experimental techniques reveal the formation of rectangular mounds for sufficiently large angles of incidence that are initially elongated in the direction perpendicular to the deposition plane of incidence. The simulations show a transition from perpendicular to parallel orientation, which occurs through pyramid formation at a coverage that depends on the angle of incidence and the substrate temperature. The elongation of the islands can be quite strong, leading to ripple formation and a very strong roughening of the growth front. The enhanced roughening of the growth front, compared to the already rough growth observed at normal incidence, is identified as super Poisson growth.