Synthesis and properties of ultra-thin YBa2Cu3O7 and YBa2Cu3O7/La2-xSrxCuO4 multilayers

Using the standard single target off-axis sputter deposition procedure, ultra-thin YBa2Cu3O7 superconducting films were made in-situ. The authors have studied the thickness dependence of superconducting properties (Tc,Jc) from 20 to 4000 Angstrom. Tc starts degrading below 125 Angstrom and falls to 50 K for the 30 Angstrom film. Jc drops linearly with decreasing thickness below 1000 Angstrom. The authors have grown Yba2Cu3O7/La2-xSrxCuO4 superconducting thin film multilayers in-situ by the same process. The modulation wavelength of the multilayers ranged from 45 Angstrom to 2000 Angstrom. X-ray diffraction and cross sectional TEM confirm the superlattice periodicity. The superconducting transition temperature drops in much the same way as the single layer ultra-thin films. Both the critical current density and its magnetic field dependence decrease as the modulation wavelength decreases