Control of In-Plane-Orientation of Bi-2212 Thin Films Prepared by the Metal-Organic Decomposition Method

We have prepared Bi₂Sr₂CaCu₂O_x (Bi-2212) thin films on MgO (100) substrates by a metal-organic decomposition (MOD) method for applications in the high frequency range. The lattice mismatch in the ab-plane between Bi-2212 and MgO is 9.2%, and it has been reported that the in-plane orientation contained small fractions of rotation angle eta ap plusmn12deg (i.e. [100] of Bi-2212 // [510] of MgO) in addition to cube-on-cube textured growth. In order to prevent these fractions, we fabricated a SrTiO₃ (STO) buffer layer on the MgO substrate by MOD because the lattice mismatch between STO and Bi-2212 (2.1%) is very suitable. The in-plane orientations of the STO thin film fabricated on the MgO substrate and the Bi-2212 thin film fabricated on the STO buffer layer were determined by an X-ray diffractometer with four axes. The Bi-2212 thin film on the STO buffer layer showed cube-on-cube textured growth with no fractions.