Highly reproducible large-area and double-sided pulsed laser deposition ofHTSC YBCO : Ag thin films for microwave applications

Large-area pulsed laser deposition (PLD) producing high-quality YBa2Cu3O7-x (YBCO) thin films on both sides of R-plane sapphire substrates with CeO2 b uffer layer is used routinely to optimize planar microwave stripline filter s for satellite and mobile communication systems. A relatively simple PLD a rrangement with fixed laser plume and rotating substrate, with an offset be tween the laser plume and the center of the substrate is employed to deposi t laterally homogeneous 3-inch-diameter Ag-doped YBCO thin films. The YBCO:Ag films are about 250 nm thick and have laterally homogeneous cri tical current densities of more than 3.5 MA/cm(2) at 77 K and homogeneous m aps of microwave surface resistance R-s of about 40 m Omega at 145 GHz and 77 K. The R-s at 8.5 GHz and 77 K, determined in the center position of the YBCO:Ag films, remains constant at about 370 mu Omega up to a microwave su rface magnetic field of about 10 mT. After experience with more than 700 do uble-sided 3-inch-diameter films, a high degree of homogeneity and reproduc ibility of j(c) and R-s is reached. The PLD-YBCO:Ag films are suitable for microwave applications envisaged for future communication systems.