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-target rf magnetron sputtering under a high pressure of 0.5 Torr. During growth, film deposition materials are supplied alternately from Bi2Sr2Cu1.3Oy and CaCuOy targets to control the number of CuO2 layers. It is demonstrated that a sputtering gas pressure higher than 0.3 Torr effectively reduces the compositional deviation, which is normally caused by the resputtering effect. It is also demonstrated that alternate deposition from the two targets leads to controlled epitaxial growth with the c-axis perpendicular to the substrate. As grown epitaxial films thus prepared exhibit superconductivity at a T-c as high as 79 K for Bi2Sr2CaCu2Oy films and 8 to 11 K for Bi2Sr2CuOy films.