Dynamics and stability of nanostructures on metal surfaces

Ultrathin metal films consisting of two-dimensional clusters are typically unstable: the cluster ensemble has the tendency to reduce its total free en ergy via Ostwald ripening or dynamic coalescence of mobile clusters. In thi s paper we give an overview of recent model experiments addressing these co arsening mechanisms. The experiments have been performed using STM on ensem bles consisting of adatom or vacancy clusters with typical diameters in the nanometer range on fcc(lll)-metal surfaces. Agreement with and deviations from conventional theories are discussed.