Technical: This project addresses current carrying capability in high-temperature superconductor (HTS) films. The focus of the project is on novel experimental approaches, such as incorporation of porosity by nanoscale strain effects, and physical properties of HTS films. Three topics will be investigated: 1) physics of critical current density in single HTS nanobridges and networks of HTS nanobridges fabricated using e-beam lithography. The HTS materials include YBCO), Tl-based (Tl-HTS) and Hg-based (Hg-HTS) superconductors; 2) porous YBCO films via a process that combines vicinal growth and nanoparticle insertion. The mechanism of pore initiation and pore evolution will be studied to increase basic understanding and for its use toward achieving control of pore morphology, density, and interface features. Electric transport properties will be assessed to understand and utilize correlation between microstructure and transport properties in formulating schemes for HTS devices with high current carrying capability approaching theoretical limits. 3) focus will be on the microscopic growth mechanism of linear defects, specifically nanotube pores through micrometer thickness of YBCO films.
The project addresses basic research issues in a topical area of electronic materials science with high technological relevance. Research and educational activities will be integrated by involvement of undergraduates in the research program, and incorporating new research results into the classroom, striving for forefront education to the next generation in nanoscience, material science, and physics.
The proposed research in manipulating superconductivity at nanoscales explores fundamental physics for controlling the behavior of electrons in superconductors via development of nanostructures (nanotubes, nanorods, nanoparticles, etc) in high temperature superconductor thin and thick films. This research is at the interface between nanoscience, material science, and material physics, will focus not only on understanding the microscopic mechanisms of the nano-composite (epitaxial thin films matrix with embedded nanostructures) thin film processes, but also the fundamental physics occurs at such a microscopic scale. The emphases of the project are on both fundamental physics and material science of the high temperature superconductors and their applications in electronics and electrical devices including microwave filters, superconducting cables, power generators, transformers, magnets, etc. The goal is to functionalize the materials for various applications. The success of the proposed research is of primary importance to the fundamental material research through development of novel processes for synthesis and can have a broad impact to other disciplines since the developed approaches can be applied to a broad spectrum of technological important materials including superconductors, semiconductors, ferroelectric and magnetic materials. In addition, the development of these novel processes also generates novel nanostructures of rich physics at microscopic scales. The integrated experimental and theoretical approaches we have been developing in this project combine recent techniques in nanoscience and material science/physics can have a broad impact on general material research, in particular materials by design through understanding of behaviors of electrons, phonons, their interactions with other particles like photons and vortices. The applications enabled by this research cover many areas including power industry, telecommunication, and medicine. The broader impacts of this research include not only the novel research methodologies that can be applied to many other technologically interesting materials, but also the forefront education to the next generation in nanoscience and material science/physics. The proposed research at the interface of materials science and nanotechnology involves many advanced research skills in both theoretical modeling and experimental fabrication/characterization. On theory side, the students will be trained with modeling of macroscopic elastic strain with consideration of microscopic interfaces between lattice mismatched materials at nanoscales. Understanding of effect of the modulated strain on the self-assembly of nanostructures in the ceramic matrix film will provide insights on controlling parameters in experimental growth of the functionalized nano-composite ceramic films. The experimental training includes thin film epitaxy using various vacuum based physical vapor deposition methods including magnetron sputtering, electron-beam evaporation, pulsed laser deposition, and atomic layer deposition, thin film characterization using XRD for structure, scanning probe microscopy and scanning electron microscopy/energy dispersive x-ray spectroscopy for surface morphology, chemical composition, and electronic states at nanoscales, electro-magnetic measurement of superconducting properties using SQUIDs magnetometer and electric transport measurement. Nanoscale device fabrication will be an additional part of the training at the KU Nanofabrication Facility, which PI is in charge, using photolithography, nanoimprint lithography and electron-beam lithography.
