9624021 Anlage The objectives are: to understand the basic nature of the superconductor (SC) proximity effect, use this understanding to engineer qualitatively new SC materials, and study the physics of cuprate Scs through their microwave surface impedance (MSI). Both low-Tc and high-Tc SC materials, in both thin-film and bulk form, will be prepared and characterized. The MSI will be measured by two resonance techniques developed by the group. The research should lead to our deeper understanding of low-Tc superconductivity, the symmetry of the ground-state wavefunction of cuprate Scs, the influence of fluctuations on the physical properties of cuprates, and a clarification of the physical properties of the rogue electron-doped cuprate SC, as well as some novel applications of superconductors. %%% Superconductivity is one of the many intriguing phenomena that have come to light as scientists have explored the realm of very low temperatures.And one of the most astonishing features has been the "proximity effect" whereby a superconductor can sometimes induce superconductivity in a nearby normal material. In this program, we shall conduct experiments designed to deepen our understanding of this effect and of superconductivity in general, and to engineer qualitatively new superconducting materials. ***