Metal Surfaces, Quantum Wells, and Superlattices

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A study of the structure, growth behavior; and properties of selected metal surface, interfaces, overlayers, quantum wells, multilayers, and superlattices is proposed. The purpose is to obtain a fundamental understanding of the scientific principles that govern the crystalline form, chemical composition, and electronic properties of metal epitaxial systems and quantum structures. The experimental techniques to be employed include (angle-resolved) synchrotron photoemission, Auger spectroscopy, electron diffraction, scanning tunneling microscopy and spectroscopy, and grazing-incidence X-ray diffraction. Samples will be prepared and fabricated using standard ultrahigh vacuum techniques as well as molecular beam epitaxy and chamical vapor deposition. The work will include investigation of bulk and surface band structure, coherence and scattering lengths, and spatial distributions of electronic states; adsorption geometry, cluster and island formation, and film growth behavior; evolution of surface, interface, and quantum-well states as a function of sample structure; atomic structure of buried interfaces; coupling between quantum wells; and phenomena pertaining to superlattices and multilayer structures. %%% Artificial structures made of stacks of thin layers can exhibit interesting and potentially useful electronic properties. Using state-of-the-art techniques for materials synthesis, it is now possible to fabricate layer configurations with layer thicknesses approaching the atomic dimension. In such systems, electrons can become trapped, reflected, or refracted by the boudaries between layers. Because these happen on an atomic scale, substantial modifications of the electronic properties can be achieved by tailoring the structure. This research project will employ a variety of experimental techniques to address the basic questions concerning the growth and characterization of various layer configurations, and the relationships between the atomic structure and the electronic properties. Part of the work will be carried out at the Synchrotron Radiation Center at Madison, Wisconsin and the National Synchrotron Light Source at the Brookhaven National Laboratory. This research involves a cooperation between work supported by the National Science Foundation and the Department of Energy.