Additive-enhanced coarsening and smoothening of metal films: Complex mass-flow dynamics underlying nanostructure evolution

Many of the phenomena that we see in everyday life,whenever a liquid interacts with a solid, can also occur whena solid interacts with another solid, at least when one of thetwo solids is in the form of a very thin lm. In such a case,the thin lm can wet the other solid or not; the lm canredistribute itself spatially with time—e.g., its droplets ~clus-ters! can merge; and both behaviors can be affected by ‘‘thirdparties,’’ i.e., additives. The effect of additives, particularlyadditives that act as surfactants, has been investigated andexploited extensively in the growth of thin solid lms. How-ever, the effect of additives on mass redistribution and relax-ation after growth has been much less examined for thinsolid lms. Both are important topics, since they relate to theformation and temporal stabilities of solid nanostructures.One example of considerable technological signicance isthe use of surfactants to control the growth mode in semi-conductor heteroepitaxy, e.g., converting Stranski-Krastanovgrowth of Ge on Si~100! to quasi-layer-by-layer growth.