IN-SITU EPITAXIAL-GROWTH OF SUPERCONDUCTING BI2SR2CAN-1CUNOY (N=1,2) THIN-FILMS BY 2-TARGET MAGNETRON SPUTTERING UNDER HIGH-PRESSURE

In situ superconducting thin films of Bi2Sr2Can-1CunOy (n = 1, 2) are grown epitaxially on SrTiO3 (100) and MgO (100) substrates by two-targ et rf magnetron sputtering under a high pressure of 0.5 Torr. During g rowth, film deposition materials are supplied alternately from Bi2Sr2C u1.3Oy and CaCuOy targets to control the number of CuO2 layers. It is demonstrated that a sputtering gas pressure higher than 0.3 Torr effec tively reduces the compositional deviation, which is normally caused b y the resputtering effect. It is also demonstrated that alternate depo sition from the two targets leads to controlled epitaxial growth with the c-axis perpendicular to the substrate. As grown epitaxial films th us prepared exhibit superconductivity at a T-c as high as 79 K for Bi2 Sr2CaCu2Oy films and 8 to 11 K for Bi2Sr2CuOy films.