Enhancement of critical current density in YBa2Cu3O7−δ thin films grown using PLD on YSZ (001) surface modified with Ag nano-dots

Y123 thin films were grown by pulsed laser deposition (PLD) on YSZ (001) substrate. Prior to the film deposition, a discontinuous layer of Ag was deposited on the substrate, also using PLD, in the form of separate islands. Atomic force microscopy (AFM) investigation of the Ag layer showed that its morphology consisted of self-assembled islands of nanometre size, randomly distributed on the surface of the substrate, called nano-dots. The Y123 superconducting films grown on such a surface were characterized using AFM, x-ray diffraction, secondary electron microscopy, ac susceptibility and dc magnetization. The results show that there is no significant difference in surface morphology, crystallographic orientation, phase composition or superconducting transition temperature between the Y123 films grown on YSZ (001) with an Ag nano-dots layer and a control Y123 film grown on a virgin YSZ (001) surface. On the other hand, at 77 K, the magnetic critical current density ( ) was three times higher for the Y123 film grown on YSZ with the modified (001) surface than for the film grown on YSZ with a virgin (001) surface. At 5 K the enhancement of was approximately seven times, at both low and high fields. This suggests an increase in pinning, caused presumably by point defects formed in the Y123 film above the Ag islands.