****Technical Abstract**** Epitaxy plays a pivotal role in the fabrication of solid state and organic semiconductor devices, creation of strain relief nanostructured arrays, and design of coatings with novel optical and mechanical properties. Understanding the microscopic details of the various growth processes at work continues to be a central focus of surface and materials science research. In recent work colloidal suspensions were used to show that dynamic mechanisms based on the diffusive motion of particles moving between interstitial sites contribute substantially to the step edge and corner barriers that determine island morphology and ultimately the smoothness of the resulting crystalline film. These diffusive mechanisms suggest new routes towards controlling film morphology. To make progress on this question this project will integrate techniques in colloid science to investigate the effects that diffusive Brownian particle dynamics have on heteroepitaxy and melting. In particular, the role played by these diffusive dynamics in setting growth and melting rates as well as the interparticle interactions on substrates that are incommensurate with the prefered lattice spacings of the particles will be determined. Ultimately these investigations will suggest new routes for controlling thin film morphology during self assembly and epitaxial growth of crystals. Since these processes are ubiquitously used in nanotechnology and semiconductor fabrication, discoveries made during these investigations have the potential to fundamentally shift practices used in these industries. This project will support the education of PhD students as well as develop a number of outreach activities including the organization of scientific workshops and the development of educational materials for K-12 teachers in various disadvantaged communities.
****NON-TECNICAL ABSTRACT**** Why do some materials grow near-perfect crystals with mirror-smooth faces whereas others grow rough, bumpy crystals? Recently, the real time growth crystals was directly observed? not by watching individual atoms, but rather by freezing model atoms that can be observed directly with an optical microscope. Using a solution of tiny plastic spheres 50 times smaller than a human hair, conditions that lead to crystallization on the atomic scale were reproduced. In addition to simply watching the particles crystallize it was shown that the random darting motion of a particle is a key factor that determines how easily particles can move off a growing island. When particles can hop off islands more easily, smooth crystals are grown. This project will build on these results and investigate both crystallization and melting on surfaces that strain the crystals. Application of these findings to the atomic scale will enable better control over the growth and melting of thin films used to manufacture electronic components for our computers and cell phones. This project will support the education of PhD students as well as develop a number of outreach activities including the organization of scientific workshops and the development of educational materials for K-12 teachers in various disadvantaged communities.
