A molecular statics study was made of surface diffusion barriers; especially facet–facet and step–facet types. The study focused on 2 high-symmetry surfaces or facets: {111} and {100}. The results showed that these 2 barriers were distinct from conventional step barriers, and were independent of facet size when it exceeded 3 atomic layers. The facet–facet barrier was usually substantially larger than the diffusion barriers on flat surfaces or down monolayer steps. The step–facet barrier was substantially larger than the diffusion barriers along, or across, monolayer steps. There were exceptions. When two {100} facets were involved, the 2 barriers decreased as the size of the end facet increased from 1 to 2 layers, and then increased from 2 to 3, or more, layers. Due to the large facet–facet and step–facet barriers, the surfaces of thin films were of the order of 100nm. The small facet–facet and step–facet barriers between two {100} facets, when the end facet was 2 to 3 layers, made it difficult to form another {100} facet near to one {100} facet. For the same reason, nanowires along <100>/{100}, on {100}, were unlikely. Nanowires along <110>/{111} were possible.

Diffusion Barriers on Cu Surfaces and Near Steps. J.Wang, H.Huang, T.S.Cale: Modelling and Simulation in Materials Science and Engineering, 2004, 12[6], 1209-25