A density functional study of silver clusters on a stepped graphite surface: formation of self-assembled nano-wires

Abstract

Adsorption and diffusion of silver adatoms and clusters containing up to eight atoms on an HOPG substrate with an armchair step are studied using density functional methods. Step edges act as attractive sinks for adatoms and clusters. The diffusion barrier of an Ag adatom along the step edge is much larger than that on a clean terrace. At zero temperature, Ag clusters either distort or dissociate by forming covalent bonds with the edge C atoms. At 600 K, Ag5 and Ag8 clusters diffuse to the step edges, and then break up so as to maximize Ag-C bonds. The Ag atoms try to form a nanowire structure along the step edge. At such high temperatures, diffusion of clusters along the step edge involves diffusion of individual Ag atoms not bonded to the edge C atoms. Assumption of complete immobility of clusters trapped at step edges in the Gates-Robins model is not valid at high temperatures in this particular system.

Properties of Highly Oriented Pyrolytic Graphite Supported TaSi16 Clusters: A Density Functional Investigation

“…In low-energy cluster beam deposition (LECBD) experiments, clusters land on the substrate randomly, and they can approach the substrate at any point and in any random orientation. To mimic this process we used the random rotation method which we developed earlier. , In this method, random orientations of the cluster on the substrate are generated by treating it as a rigid body and choosing the Euler angles of rotation randomly. The TaSi 16 cluster was placed above the special symmetry sites α, β, hollow, and bridge on HOPG.…”

“…To mimic this process we used the random rotation method which we developed earlier. 28,44 In this method, random orientations of the cluster on the substrate are generated by treating it as a rigid body and choosing the Euler angles of rotation randomly. The TaSi 16 cluster was placed above the special symmetry sites α, β, hollow, and bridge on HOPG.…”