Department of Physics and Astronomy

University of North Carolina, Chapel Hill, NC 27599, USA

Abstract:

Combinatorial synthesis and characterization are a set of powerful techniques for rapid assessment and analysis of new materials and properties.  The use of the high throughput approach is expected to play an increasingly critical role in the materials development and innovation processes.  In this talk we describe new development in the combinatorial molecular-beam-epitaxial (MBE) synthesis and characterization techniques.  Epitaxial thin films and heterostructures of magnetic alloys have been investigated as a continuous function of alloy composition.  Synchrotron-based high throughput techniques have been developed to explore structural and chemical ordering in these materials.  One of the major challenges in the study of alloys has been to detect and quantify lattice site-specific chemical disorders, including site-swapping, antisites, and vacancies.  The difficulty is due primarily to comparable atomic numbers and nearly identical bond lengths between the constituent elements.  The use of a multiple-edge anomalous diffraction (MEAD) technique, x-ray diffraction versus energy in the vicinities of multiple elemental absorption-edges, promises to overcome the difficulty.  We have employed MEAD experiment and analysis for the first time to examine the nature of a variety of elemental disorders within the unit cell and their dependences on chemical composition and epitaxial constraints. Sensitivity and precision at sub-percent levels of the disorders have been successfully demonstrated.

Brief bio:

Frank Tsui received the B.S. degree in engineering physics with honors from the University of California at Berkeley in 1984, the M.Eng. degree in applied and engineering physics from Cornell University in 1986, and the M.S. and Ph.D. degrees in physics from the University of Illinois at Urbana-Champaign in 1987 and 1992, respectively.

He was a Margaret and Herman Sokol Postdoctoral Fellow in the Sciences at the University of Michigan at Ann Arbor, before he joined the faculty of the University of North Carolina in 1995 as an Assistant Professor of Physics. He is currently a Professor and Associate Chair in the Department of Physics and Astronomy at the University of North Carolina at Chapel Hill. The focus of his research has been atomic scale synthesis and characterization of nanoscale magnetic materials, including novel high throughput synthesis and characterization of epitaxial magnetic thin films and heterostructures using combinatorial molecular beam epitaxy techniques.

Professor Tsui is a member of the American Physical Society. He was an IBM Predoctoral Fellow at the University of Illinois at Urbana-Champaign. He was a recipient of the US National Science Foundation CAREER award in 1997

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