Optimization of large-area YBa₂Cu₃O_7–δ thin films by pulsed laser deposition for planar microwave devices

This paper presents high quality YBa₂Cu₃O_7–δ (YBCO) thin films on LaAlO₃ substrate for microwave devices prepared by pulsed laser deposition (PLD). The double-sided YBCO films cover a large area and have been optimized for key parameters relevant to microwave device applications, such as surface morphology and surface resistance (R_s). This was achieved by improving the target quality and increasing the oxygen pressure during deposition, respectively. To evaluate the suitability of the YBCO films for microwave devices, a pair of microwave filters based on microstrip fabricated on films from this work and a commercial company were compared. The results show that the YBCO films in this work could completely meet the requirements for microwave devices.