High quality YBCO thin films - laser deposition, co-evaporation, and device fabrication
| Autor: | Dag Winkler, M. Danerud, H. Olin, Tord Claeson, U. Engstrom, Jose A. Alarco, G. Brorsson, Zdravko Ivanov, Per-Åke Nilsson |
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| Rok vydání: | 1991 |
| Předmět: |
Superconductivity
Fabrication Materials science business.industry Condensed Matter Physics Laser Evaporation (deposition) Atomic and Molecular Physics and Optics law.invention law Proximity effect (superconductivity) Optoelectronics Grain boundary Thin film business Mathematical Physics Deposition (law) |
| Zdroj: | Physica Scripta. 44:95-101 |
| ISSN: | 1402-4896 0031-8949 |
| Popis: | High quality superconducting YBa2Cu3O7-δ (YBCO) thin films were fabricated with ex situ co-evaporation on SrTiO3 and in situ laser deposition on (001) MgO substrates. The co-evaporated films gave a superconducting transition temperature, Tc ~ 90 K, and a critical current density, jc ~ 5 × 105 A/cm2 at 77 K after an ex situ post anneal at 890°C. For laser deposited films, Tc was above 90 K, and jc, about 106 A/cm2 at 77 K. Two kinds of Josephson weak links were developed. The first kind consisted of a 0.8 μm or wider constriction in a co-evaporated YBCO film. A lift-off stencil was used to pattern the film before the post anneal. The second kind of weak link utilized the inherent grain boundaries in the laser deposited YBCO film. A 70-130 nm wide strip in A1 was deposited across a 4-6 μm wide YBCO bridge. After a 10-20 min long anneal at 300-450°C, the A1 had diffused into the film. We believe that the diffusion occurs mainly along the grain boundaries. By the proximity effect, the normal metal weakened the superconductivity at the grain boundary, and a weak link was formed with IcRn ~ 0.9 mV at 77 K. Dry an wet etching were also used to pattern some structures. |
| Databáze: | OpenAIRE |
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