ABSTRACT

Transport phenomena play a fundamental role in a diverse range of chemical, biological, and physical processes. Examples of long-range diffusional transport processes include the migration of electronic charge carriers, which are necessary for the operation of emissive displays; the transport of ions necessary for the operation of electrochemical energy storage devices, such as batteries; and the migration of large macromolecules in spatially restricted environments, such as the translocation of DNA across bacterial membranes. Morphological features (phases of differing chemical composition, and

/or varying atomic or molecular organization and different size distributions, etc.) of materials profoundly influence material properties, ranging from magnetic, optical, and electronic to corrosion and mechanical properties. Annealing a material generally induces long-range atomic and molecular transport processes, which facilitate microstructural evolution. The growth of various crystalline phases of materials during annealing is controlled by atomic or molecular diffusion processes. The spatial distribution of dopants in semiconductors, which controls device performance, is determined by atomic diffusion properties. Interdiffusion between semiconductor multilayer films that make up quantum well heterostructures (components of high-speed and high-frequency digital and analog devices) influences the optical and structural properties of the heterostructures and, therefore, device performance. Clearly, the impact of diffusional transport processes on our everyday lives is profound.