Dependence of crystalline orientation on film thickness of sputtered YBa2Cu3O<f>7−x</f> on an MgO substrate

We have systematically investigated dependence of crystalline orientation on film thickness of sputtered YBa2Cu3O<f>7−x</f> (YBCO) on an MgO substrate by the X-ray diffraction (XRD) method, the <f>φ</f> diffraction method and atomic force microscope (AFM). From examination of crystalline orientation by XRD method and in-plane orientation by the <f>φ</f> diffraction method, for thinner film below about 500 nm, the YBCO film is oriented with the <f>c</f>-axis perpendicular to the MgO substrate surface. For thicker film above about 500 nm, the <f>c</f>-axis oriented grains in the YBCO film vanish entirely and the <f>a</f>-axis oriented grains are formed. The rectangular images of <f>a</f>-axis oriented grains are also observed on the surface by AFM. We found that the crystalline orientation change drastically from <f>c</f>-axis oriented films to <f>a</f>-axis oriented films with increasing film thickness. [Copyright &y& Elsevier]