Synthesis and characterization of Bi2Sr2Can−1CunOy(n=1–7) thin films grown by off-axis, three 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 (004_0_) line of the n=7 film, can be clearly observed below 2θ<60° 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, Tc zero, decreases systematically with n. For n=7, Tc decreased to onset 55 K and end 4 K. The systematic decrease in Tc zero with n can be accounted for by a combination effect of the hole concentration decrease and crystal defect increase with n.