Sputter deposition of large-area double-sided YBCO superconducting films

Abstract

Abstract: Research in the field of high-temperature superconducting films has progressed from the study of their basic chemistry and structure, to a point where an enormous range of desirable properties are being explored for device applications. This review focuses on the synthesis and properties of large-area double-sided YBa 2 Cu 3 O 7 – δ (YBCO) films and thickness-dependent superconductivity. Double-sided YBCO thin films were prepared by sputter deposition. In order to achieve good performance and lateral homogeneity of large-area (up to 3-inch) films for multi-pole devices or low frequency application, we developed a special modulated biaxial rotation by designing a special substrate clamp, combining the out-of-plane rotation with an automatic interval in-plane rotation, and simultaneously changing the rotation speed periodically in every out-of-plane revolution (namely, modulated biaxial rotation). The biaxial rotation and its development was also used to partially avoid the negative oxygen ion bombardment that resulted from the plate target geometry. The high-quality YBCO thin films were deposited on the various single-crystal substrates such as LaAlO 3 , SrTiO 3 , MgO with typical electronic properties: superconducting transition temperature ( T c ) 90 K, critical current density ( J c ) 2–4 MA/cm 2 at 77 K in self-field and microwave surface resistance ( R s ) 0.5 μΩ for 10 GHz at 77 K, which were successfully applied to prepare high performance microwave devices including resonators, oscillators, and filters. In this chapter, the thickness dependence on residual stress and superconducting properties in YBCO films was also investigated. The results demonstrated that the values of T c and J c were strongly dependent on the film thickness. This chapter outlines the reasons underlying the calculation of residual stress in films and demonstrates the levels of control that are now possible.