Magnetron sputter deposition of a 48-member cuprate superconductor library: Bi$_2$Sr$_2$Y$_x$Ca$_{1-x}$Cu$_2$O$_{8+\delta}$ (0.5$\le x \le$1) linearly varying in steps of $\Delta x = 0.01$.

Using magnetron sputtering, a spatial composition spread approach was applied successfully to obtain 48-member libraries of the Bi$_2$Sr$_2$Y$_x$Ca$_{1-x}$Cu$_2$O$_{8+\delta}$ (0.5$\le$x$\le$1) cuprate superconducting system. The libraries were deposited onto (100) single crystal MgO, mounted on a water cooled rotating table, using two targets: the antiferromagnetic insulator Bi$_2$Sr$_2$YCu$_2$O$_{8+\delta}$ (P=98 W RF) and the hole doped superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (P=44 W DC). A low chamber pressure of 0.81 mTorr argon is 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 is used to post-anneal the amorphous deposited films following a step annealing regime - ramp at 5 $^{\circ}$C/s for heating and cooling, with a first plateau at 780 $^{\circ}$C held for 200 s, and a second at 875 $^{\circ}$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 {\AA} (x=0.5) to 30.24 {\AA} (x=1.0) with increasing Y-content, consistent with bulk values. The films are polycrystalline, developing preferred orientation 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.