NSF/ONR: Advanced Processing, Characterization and Properties of Epitaxial Multilayer Superconductor Heterostructures and Devices

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9421718 Narayan Understanding of the structure and properties of interfaces between high-temperature superconductors, metals and dielectrics holds key to the properties of thin film epitaxial structures. The structure and chemical composition of interfaces determines the nature of epitaxial growth and defects in thin films which directly affect transport properties and device characteristics. The objective of this proposal is: In-situ processing of multilayer heterostructures needed for advanced superconductor devices. The primary focus will be on yittria, barium oxide, and copper oxide superconducting materials systems. Thin film multilayer heterostructures will be processed by pulsed laser deposition using a multitarget holder where up to five different films can be grown in a single chamber. By replacing one of the targets with a laser mirror it is possible to channel the laser energy on the substrate and achieve in-situ atomic level cleaning. Modeling of stresses and strains will be carried out to understand the nature of epitaxial growth and defect content in thin films. These results will be correlated with atomic structure and chemical composition of interfaces and nature of defects in thin films. Epitaxial quality and defect content of thin films will be optimized to achieve highest theoretical superconducting temperature Tc (about 94 Kelvin) and critical current density (Jc greater than 5.0 million amps. per square cm at 77 Kelvin) for high performance devices. The optimized thin films will be used to fabricate a few high-performance bolometers (high responsivity or high speed). Superconducting materials offer an attractive energy conserving way of transmitting electricity with very low losses. However, in order to capitalize on this superconducting property, the material has to be super cooled. Further, for practical applications these superconductors have to be built into devices. In order to maximize the application, one needs to operate these devices with m inimum degree of cooling. By understanding the process of multilayer superconducting devices, it is anticipated that a broader application of this technology may become possible into new electronic devices. ***