This experimental research project focuses on the controlled fabrication of tunnel barriers intended to permit tunneling and transport studies of superconductors that are subject to strong electron correlations and to reduced dimensionality. A topic of interest is the nature of the superconductor-insulator transition in lower dimensional systems. A further topic is the search for a useful analogy between two-dimensional disordered superconductors and high Tc cuprate superconductors. Samples of varying dimensionality are to be studied by means of transport, tunneling, and scanning tunneling microscopy, emphasizing the effects of dimensional crossover and disorder. %%% This experimental research project is based on use of the technique known as electron tunneling, and in particular on finding methods to fabricate barriers suitable for the use of this technique. Electron tunneling is a quantum-mechanical process by which an electron can pass a potential barrier or "hill", which could not be overcome under the rules of classical physics, governing macroscopic objects like planets and tennis balls. Quantum mechanics allows such hills to "tunneled under" on a probabilistic basis with measurable rates of transfer limited to cases of very small mass and short (Angstrom scale) distances, such as the case of electrons in atoms. The technique of electron tunneling is important in determining the density of states, especially in superconductors; and also as the basis for the scanning tunneling microscope. This research project probes the effects of atomic scale disorder and geometric configuration on transport, with emphasis on the metal-insulator transition. Geometries of interest include planar and one-dimensional linear samples. Results from this research may include unusual new effects or st ructures which may find application in technology. This research project is interdisciplinary in nature and involves graduate and postdoctoral students who will be excellently trained to enter positions in industry, government or education. ***
