YBACUO THIN-FILMS ON SAPPHIRE UP TO 2-INCH-DIAMETER FOR MICROWAVE APPLICATIONS

YBa2Cu3 O-7-delta (YBCO) thin films on R-plane sapphire up to 5-cm-dia m with ZrO2:Y (YSZ) buffer layers were fabricated by in-situ off-axis DC magnetron sputtering and laser ablation. The film de properties, cr itical current density (J(c)), effective microwave surface resistance (R(s)), X-ray data and surface morphology as functions of deposition t emperature (T-d) from. 600 to 750 degrees C were studied. We have foun d out that the two processes simultaneously and in different ways affe ct the YBCO layers superconducting properties versus T-d. The results show that Alms deposited at bath ends of T-d range have equal critical temperatures but their J(c) and R(s) differ up tea an order of magnit ude. High-homogeneity 5-cm-diam films with J(c) > 4 MA/cm(2) and R(s) <0.8 m Omega at 10 GHz, and 77 K were routinely fabricated under optim um growth conditions. The effective 2 GHz short-dipole antenna and Wil kinson divider were developed and fabricated from the films.