FRG: Quantum Engineering of Metallic Nanostructures

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This project addresses effects of quantum confinement on epitaxial growth of metal/semiconductor thin films and nanostructures. The approach is a combined theory/experiment collaborative activity among researchers at U. Tx/Austin and ORNL, and is aimed at greater understanding and utilization of an "electronic growth" concept. To date, the main findings of the "electronic growth" model are that a competition between quantum confinement, charge spilling, and interface-induced electron density os-cillations can make a flat ultrathin metal film critically, magically, marginally stable, or totally unstable against morphological roughening. For Ag on GaAs and other III-V semiconductor substrates, the electronic growth mechanism leads to the existence of a critical thickness for the formation of an atomically flat film. Theoretical studies also showed the existence of magic thicknesses for other metal/semiconductor systems, and the possibility of oscillatory metal-nonmetal transitions. The theo-retical and experimental scope of this project will include quantum effects in both the vertical and lat-eral directions and the interplay between thermodynamic and kinetic factors. The goal is to gain a deeper understanding of the pathways of the electronic mechanism for film growth, and to achieve controlled formation of lower-dimensional structures. The possibility of using electronic energetics as-sociated with quantum states and charge quantization to influence geometric ordering and size selec-tion of quantum dot arrays will also be explored. Theoretical predictions of critical/magic thicknesses and oscillatory metal-nonmetal transitions in a variety of systems will be studied experimentally.%%% The project addresses basic research issues in a topical area of materials science with high technologi-cal relevance. The basic knowledge and understanding gained from the research is expected to contrib-ute to next generation electronic/photonic materials. An important feature of the program is the inte-gration of research and education through the training of students in a fundamentally and technologi-cally significant area. The project is co-supported by the DMR/EM and DMR/MET programs.