Fabrication and characterization of superconducting (Cu, C)Ba2CuO4±δ thin films

We have investigated the structural modulation and variation of superconducting transition temperature of (Cu, C)Ba2CuO4±δ ((Cu, C)-1201) thin films prepared by rf magnetron sputtering on (1 0 0) SrTiO3 single crystal substrates in the off-axis configuration. Thin films were deposited in a gas mixture of Ar, O2 and CO2 where the Ar:O2 ratio was kept constant at 1:2 with a total pressure of 15 mTorr and CO2 gas pressure was varied between 1 and 3 mTorr. XRD patterns revealed the formation of high quality thin films with c-axis oriented perpendicular to the plane of the substrate. The value of the c-lattice parameter varied in the range, c = 8.29-8.33 Å. These films had a superconducting resistive transition temperature (Tc onset) ranging between 25 and 40 K above which, almost all films showed semiconductor like behavior. Superconductivity in (Cu, C)-1201 thin films was further confirmed by the diamagnetic response observed in ac susceptibility measurement.