Magnetron sputter deposition of a 48-member cuprate superconductor library: Bi 2Sr 2Y xCa 1− xCu 2O 8+ δ ( [formula omitted]) linearly varying in steps of [formula omitted

Abstract

Using magnetron sputtering, a spatial composition spread approach was applied successfully to obtain 48-member libraries of the Bi 2Sr 2Y x Ca 1− x Cu 2O 8+ δ ( 0.5 ≤ x ≤ 1 ) cuprate superconducting system. The libraries of each system were deposited onto (1 0 0) single crystal MgO, mounted on a water cooled rotating table, using two targets: the antiferromagnetic insulator Bi 2Sr 2YCu 2O 8+ δ ( P = 98 W rf) and the hole doped superconductor Bi 2Sr 2CaCu 2O 8+ δ ( P = 44 W dc). A low chamber pressure of 0.81 mTorr argon was used to reduce scattering by the process gas. To minimize oxygen resputtering a substrate bias of − 20 V was used, as well as a process gas free of oxygen. A rapid thermal processor was used to post-anneal the amorphous deposited films. A step annealing regime was used, with a ramp rate of 5 ° C/s for heating and cooling, with a first plateau at 780 ° C held for 200 s, and a second at 875 ° C held for 480 s. X-ray diffraction reveals that the films develop crystalline order with the c-axis lattice parameter contracting linearly from 30.55 Å ( x = 0.5 ) to 30.24 Å ( x = 1.0 ) with increasing Y-content, consistent with bulk values. The crystallized films are polycrystalline, developing preferred orientation ( c-axis parallel to the substrate) for thinner members of the library. There is a change of 0.01 in doping per library member which will enable further studies to densely map phase space.