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My research program investigates the fundamental aspects of nonequilibrium processing of materials by ion beams, consolidation of nanoscale powders, and low-temperature diffusion. Ion implantation has long been employed in the semiconductor industry as a highly controlled method of doping semiconductors. However, a host of new technologies using ion beams for processing has been developed in recent years, including ion beam mixing, beam-assisted deposition, and ionized cluster beam deposition. These various methods are studied in the laboratory by several advanced characterization methods: ion-beam analysis, X-ray diffraction, secondary ion mass spectroscopy, Auger spectroscopy, and transmission electron microscopy. They are investigated theoretically by computer simulation using molecular dynamics methods. The computer simulations are performed on Cray-2 supercomputers at the UIUC National Center for Supercomputing Applications and the Magnetic Fusion Energy Computer Center at Lawrence Livermore National Laboratory. A variety of materials are being studied: metals and intermetallic compounds for advanced reactor technologies, GaAs-AlAs superlattices for quantum well lasers, metal-on-semiconductors for device interconnects, and metallic glasses for various applications.

A new method of synthesizing novel materials nanocrystal processing is also being studied. Here, small particles, typically 5-10 nm in size, are produced by inert or reactive gas condensation; they are subsequently cold compacted in an ultrahigh vacuum environment. Because these materials can have 30-50% of their atoms on grain or interface boundaries, they often possess far different thermodynamic, magnetic, and optical properties than their bulk counterparts. Moreover, they reveal exceptional sintering and deformation properties that make them particularly appealing for processing traditionally brittle materials, such as ceramics and intermetallic compounds.