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

9421718纳拉扬对高温超导体、金属和电介质之间界面的结构和性质的了解是薄膜外延结构性质的关键。界面的结构和化学成分决定了薄膜的外延生长和缺陷的性质，直接影响薄膜的输运特性和器件特性。该方案的目标是：对先进超导器件所需的多层异质结构进行原位加工。主要焦点将放在氧化钇、氧化钡和氧化铜超导材料系统上。薄膜多层异质结构将通过脉冲激光沉积处理，使用多目标支架，在一个腔室中可以生长多达五种不同的薄膜。通过用激光反射镜替换其中一个靶，可以将激光能量输送到衬底上，实现原子水平的就地清洁。为了了解外延生长的本质和薄膜中的缺陷含量，将进行应力和应变建模。这些结果将与界面的原子结构和化学成分以及薄膜中缺陷的性质相关。薄膜的外延质量和缺陷含量将得到优化，以达到最高的理论超导温度T_c(约94开尔文)和临界电流密度(J_c>500万安培)。每平方厘米77开尔文)，用于高性能设备。优化后的薄膜将被用于制造一些高性能的测辐射热计(高响应度或高速)。超导材料提供了一种极具吸引力的节能方式，可以以非常低的损耗传输电力。然而，为了充分利用这种超导特性，这种材料必须过冷。此外，为了实际应用，这些超导体必须被内置到设备中。为了使应用最大化，人们需要以最低的冷却程度来操作这些设备。通过了解多层超导器件的过程，可以预期该技术可能在新的电子设备中得到更广泛的应用。***

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. ***