SYNTHESIS AND CHARACTERIZATION OF BI2SR2CAN-1CUNOY (N=1-7) THIN-FILMS GROWN BY OFF-AXIS, 3 TARGET MAGNETRON SPUTTERING

An alternate deposition method using three target magnetron sputtering and off-axis substrate geometry has been applied to control the number of CuO2 planes n in Bi2Sr2Can-1CunOy thin films. During alternate deposition, the substrate stayed sequentially at each target as Bi --> Sr5Cu2O7 --> CaCuO2 --> Sr5Cu2O7 --> Bi. When the staying times at the Bi and Sr5Cu2O7 targets were fixed constant but varied for the CaCuO2 target, single phase films with n = 1-7 were obtained. The x-ray diffraction patterns showed a systematic change in the relative line intensity with n in accordance with the calculated patterns, and all possible (00l) lines, including the (0040) line of the n = 7 film, can be clearly observed below 2theta < 60-degrees region. The c dimension increases stepwise by 0.63 nm and approaches 6.27 nm for n = 7, indicating a perovskite CaCuO2 plane is regularly inserted with n. The resistivity zero temperature, T(c) zero, decreases systematically with n. For n = 7, T(c) decreased to onset 55 K and end 4 K. The systematic decrease in T(c) zero with n can be accounted for by a combination effect of the hole concentration decrease and crystal defect increase with n.