Kinetics-limited surface structures at the nanoscale

Abstract

This letter presents the evolution of kinetics-limited nanoscale structures during copper thin film deposition. We first calculate the three-dimensional Ehrlich–Schwoebel (3D ES) kinetic barrier of copper using the molecular dynamics/statics method. Based on this calculation, the dimension of {111} facets, under typical sputtering deposition conditions, is estimated to be 700 nm if the 3D ES barrier is effective, in contrast to 70 μm without it. Accompanying the calculations, we deposit copper 〈111〉 columns using the magnetron sputtering technique, and characterize their structures using scanning electron microscopy and x-ray diffraction techniques. The observed facets of pure copper films are on the order of 200 nm in dimension, confirming that surface structure is controlled by the 3D ES kinetic barrier. When indium is introduced as surfactant, the facet dimension increases, leading to conformal films; this is attributed to reduction of the 3D ES barrier.