Effect of UV Light Irradiation on the A-Axis Orientation Mechanism for Y1Ba2Cu3O7-δ Films Prepared by Laser Metalorganic Chemical Vapor Deposition

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Abstract
In previous work, we reported a very effective method of controlling the orientation of YBCO film by metalorganic chemical vapor deposition (MOCVD) using ArF excimer laser irradiation on a MgO(100) substrate. The laser power density used in the previous study was 100 mJ/cm2, which was sufficient for melting the sample surface when the substrate temperature was kept at 700°C. In this work, we investigated the laser power density and repetition rate dependence of a-axis orientation of YBCO film, in order to establish whether or not melting of the surface is an indispensable factor for a-axis orientation by laser irradiation. The surface morphology depends on the laser power density and repetition rate; however, high a-axis orientation is observed even when the film surface does not appear to be melted. The a-axis orientation was obtained only with a flowing gas source with the laser irradiation. This suggests that the nuclei of a-axis orientation are formed only when the source materials are decomposed by laser irradiation on the film surface.