Densely mapping the phase diagram of cuprate superconductors using a spatial composition spread approach

A novel spatial composition spread approach was used successfully to deposit a 52-member library of La2-xSrxCuO4 (0 <= x <= 0.18) using magnetron sputtering combined with physical masking techniques. Two homemade targets of La2CuO4 and La1.82Sr0.18CuO4 were sputtered at a power of 41 W RF and 42 W DC, respectively, in a process gas of 15 mTorr argon. The libraries were sputtered onto LaSrAlO4 (0 0 1), SrTiO3 (1 0 0) and MgO (1 0 0) substrates through a 52-slot shadow mask for which a -20 V substrate bias was applied to prevent resputtering. The resulting amorphous films were post-annealed (800 degrees C for 1 h then at 950 degrees C for 2 h) in a tube sealed with oxygen gas. Wavelength Dispersive Spectroscopy (WDS) analysis revealed the expected linear variation of Sr content from 0 to 0.18 with an approximate change of 0.003 per library member. Transport measurements revealed superconducting transitions as well as changes in the quasiparticle scattering rate. These transitions and scattering rate changes were mapped to produce the T-hole concentration phase diagram. (C) 2009 Elsevier B.V. All rights reserved.