Epitaxial MgO buffer layers for YBCO thin films on R-plane Al2O3

MgO buffer layers were epitaxially grown on R-plane Al2O3 (<1(1)under bar 02>) substrates by rf magnetron sputtering using an Mg metal target for high-T-c superconducting thin films. A c-axis oriented MgO film with a smooth and homogeneous surface was obtained at 350 degrees C in an Ar/O-2 mixture under a total sputtering gas pressure of 0.3 Torr with 4 x 10(-6) Torr O-2 High-T-c superconducting Y1Ba2Cu3O7-x (YBCO) thin films were prepared on Al2O3 substrates with and without an MgO buffer layer by de magnetron sputtering. The YBCO film on Al2O3 with an MgO buffer layer was c-axis orientatied perpendicular to the surface and exhibited zero resistivity at T-c = 80 K. A depth profile of atomic concentration and interdiffusion for YBCO (3000 Angstrom)/MgO (500 Angstrom)/Al2O3 was investigated. No diffusion of any atom was observed in the interfaces.