Microcrack-free thick YBCO/CeO2/Al2O3 films prepared by a large-area pulsed laser deposition system

High-quality YBa2Cu3O7-delta (YBCO) films were deposited on CeO2-buffered sapphire substrates using a large-area pulsed laser deposition system. Interplay of parameters such as thickness and target-to-substrate distance on the surface morphology evolution and superconducting properties of the films were examined. In particular, YBCO films with thicknesses up to similar to1.8 mum were successfully deposited with no observable microcracks on the surface. Characterization of the films revealed the following unique features: (1) a porous morphology, consisting of interconnected islands of varied heights and deep holes; (2) higher normal-state resistivity value, which is attributed to the presence of various defects in the film; and (3) Y-rich composition. These factors are considered to contribute to the strain-relieving mechanism responsible for the increase in film thickness without microcracking. Using this system, a 2" YBCO film with thickness of similar to370 nm and no observable microcracks was deposited. A microwave surface resistance value of R-s similar to 1.4 mOmega was obtained at 77.3 K at a resonant frequency of 10.7 GHz. Mapping of the critical current density (J(c)) by inductive measurement showed values of similar to1.4-1.6 MA/cm(2) at 77.3 K. (C) 2003 Elsevier B.V. All rights reserved.