Suppression of superconductivity at the nanoscale in chemical solution derived YBa2Cu3O7−δ thin films with defective Y2Ba4Cu8O16 intergrowths†
The analysis of the microstructure and superconducting behavior of chemical solution deposited epitaxial YBa2Cu3O7−δ films, with thickness going down to 5 nm has been carried out with the purpose to disclose the behavior of the most common intergrowth in these films, the Y2Ba4Cu8O16. The analysis of ultrathin films is a unique opportunity to investigate the superconducting behavior of these nanoscale defects because of the high concentration created as a consequence of the elastic energy associated to the misfit strain. Magnetic susceptibility and X-ray diffraction measurements evidence a strong decrease of the superconducting volume correlated with an increase of the intergrowth volume fraction. We demonstrate that these intergrowths are non-superconducting nanoscale regions where Cooper pair formation is disrupted, in agreement with their key role as artificial pinning centers for vortices in YBa2Cu3O7−δ films and coated conductors.