Fabrication and characterization of double-sided YBCO superconducting thin films using laser ablation

Epitaxial growth of double-sided high-Tc superconducting (HTSC) thin film has been systematically investigated since it is important for microwave applications as well as for fundamental research. We have fabricated highly c-axis oriented YBa2Cu3O7-x (YBCO) superconducting thin films on (100) MgO substrates by pulsed laser deposition (PLD), because devices like microwave stripline filters for communication systems require high-quality HTSC thin films on both sides of single crystal wafers. To use one-sided film as a low-loss ground plane, we have used a halogen lamp to heat the substrate without silver paste to preserve its backside for the fabrication of double-sided superconducting thin films. The electrical property and the structural characteristics of YBCO films have been studied by R-T measurement and X-ray diffraction. We have observed by X-ray diffraction the film orientation changes from c-axis to a-axis as the film thickness increases. Glancing-angle X-ray diffraction revealed that the film orientation was changed from fully c-axis near the substrate/film interface to a mixture of a-axis and c-axis near the film surface. This should be considered in the manufacture of superconducting microwave devices. By optimizing the thickness and the deposition temperature of YBCO thin films, highly c-axis-oriented double-sided YBCO thin films have been fabricated. The transition temperature of these films has been shown to be about 88 K.