Mechanism of selective nano structure formation on pre-patterned surfaces

A self-alignment of metal nanoclusters has been observed on ripple like pre-patterned oxidized Si surfaces by oblique angle electron-beam evaporation. During the metal deposition perpendicular to ripples the metal nanoclusters are grown on the slopes which point towards the evaporation source.The self-ordering of metal nanoclusters has not been observed for normal deposition and for low-angle deposition parallel to the ripple direction. This indicates that the features of the metal nanostructure depend strongly on the local deposition angle. With the 3D lattice kinetic Monte Carlo simulations we studied the process of silver deposition on pre-patterned surfaces. The experimentally observed Ag nanostructures could be reproduced by using the many-body potential to estimate the atomistic migration barriers. It was shown that the extremely short range of surface adatom migration causing low sticking probability together with a slope-dependent deposition rate promotes the localization of the Ag nanocluster nucleation distribution. Consequently, the observed selective Ag nano structure formation can be understood by the separation of the Volmer-Weber growth mode and the layer-by-layer growth mode due to the localized coalescence of clusters.