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- Selinder, TI, et al.
(författare)
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Microstructure and microwave loss studies on epitaxial YBa2Cu3Ox thin films
- 1992
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Ingår i: High Tc superconductor thin films. - 0444893539 ; , s. 219-224
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Konferensbidrag (refereegranskat)abstract
- Thin YBa2Cu3Ox films were grown on SrTiO3 or LaAlO3 single crystals by dc-magnetron reactive sputtering in argon/oxygen gas mixtures. Deposition temperatures ranged from 540 °C to 780 °C. After deposition and subsequent cool down, films grown above 680 °C are superconducting below 86–88 K. All films are oriented with the [001] direction parallel to the [001] substrate normal. The best films have critical current densities well above 106 A/cm2, and effective 6 GHz surface resistance values below 300 μω, at 77 K. Despite good electrical properties, the films are littered with copper rich particles on a smooth and epitaxial single crystalline surface. Cross-section Transmission Electron Microscopy (X-TEM) was used to study the crystalline quality on a microscopic level, and the nature of particles occurring on/in the as grown film. Small misaligned YBa2Cu3Ox grains often occur in the films. The large copper rich particles on the film surface seem to have nucleated at such grains on the film surface. Their occurrence can, at least partly, be explained by a nonstoichiometric flow to the substrate. The number density of the particles decreased with increasing growth temperature but the volume density seemed to be constant in the investigated temperature interval.
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