| Summary: | 碩士 === 國立臺灣大學 === 物理研究所 === 101 === An bi-epitaxial technique for the fabrication of high temperature superconducting YBa2Cu3O7-δ (YBCO) artificial grain-boundary is researched. We have studied a bi-epitaxial structure, YBCO/CeO2/MgO and YBCO/MgO boundary. The CeO2 layers are grown on MgO substrates by using RF magnetron sputtering. Then, we define the grain boundary by optic lithography and ion-milling. YBCO films are grown by pulsed laser deposition (PLD). And try to add a SrTiO3 (STO) buffer layer to avoid the lattice mismatch between the pure YBCO film and the MgO substrate. The crystalline orientation and the surface morphology are characterized by X-ray diffraction and atomic force microscope (AFM). The electric and magnetic properties are also well studied by using low temperature measurement and superconducting quantum interference device (SQUID).
The superconducting YBCO films reveal a high transition temperature Tc (R=0), and a critical current density in a zero magnetic field Jc which is large at 77 K. By measuring the characteristics of this device, and studying the properties of this superconducting thin film with grain-boundary, we find that this new structure can improve the artificial grain-boundary, and make device reveal very good properties with a high IcRn product, showing that this technique creates an opportunity to improve the fabrication of Josephson junction applications.
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