Surface diffusion was the key process responsible for mass transport on surfaces. Experiments could be carried out to measure surface diffusion either under equilibrium or non-equilibrium conditions. Equilibrium experiments could be used to measure the coverage and temperature dependence of the diffusion coefficient Dc(θ,T) which in turn was useful to deduce thermodynamic information about the system (adatom–adatom interactions, phase transitions, collective effects, etc.). Non-equilibrium experiments were more relevant to systems grown epitaxially because of the lower temperatures and higher deposition rates commonly used. Under these conditions metastable self-organized structures could be prepared within surprisingly short times, which suggested that some novel but still unclear kinetic pathways must exist at low temperatures. In addition, the failure of the quasi-equilibrium description of nanostructure relaxation for sufficiently small sizes will be discussed to stress the need for better knowledge of the kinetic barriers controlling the relaxation.

Novel Diffusion Pathways in Low Temperature Self-Organization of Nanostructures. M.C.Tringides, M.Hupalo, M.Yakes: Physica A, 2005, 357[2], 216-49