Electron and atom dynamics at solid surfaces and relation to epitaxy

At the surface, the three dimensional symmetry of a solid is broken. Electrons and atoms near the surface may rearrange to lower the free energy of the system. Scattering by defects and confinement by boundaries of electrons may produce long-range charge density oscillations. Adatoms interact with each other via mutual perturbation of the surface, known as indirect electronic and elastic interactions. These interactions are very weak and are also oscillatory. For some systems, formation of adsorption layer superstructures can be directly correlated to adatom-adatom interactions. When the temperature is raised, adatoms and admolecules can start to diffuse, interact, or react. They may aggregate into clusters and islands, and grown into a thin film. The stability of clusters may exhibit magic numbers in size and thickness. When the temperature is changed, island shape transitions may occur. The growth of islands and ultra-thin films can also be influenced by electronic effects as well as by the addition of a surfactant layer. All these growth behaviors in epitaxy can be understood from the mechanisms and energetics of elementary surface atomic processes, and atom and electron dynamics. They, in turn, can be studied in details using atomic resolution microscopy.