YBa2Cu3O7-δ/insulator multi-layers for crossover fabrication

The development of thin-film dielectrics compatible with the epitaxial growth of YBa₂Cu₃O_7-δ (YBCO) is crucial to the fabrication of multilayer device and circuit structures. The authors investigated the YBCO/SrTiO₃ (STO) system by fabricating YBCO/STO bilayers and simple YBCO/STO/YBCO crossover structures. The thin films were deposited in situ by pulsed-laser deposition and analyzed using X-ray diffraction and scanning electron microscopy. The film interfaces were characterized by secondary ion mass spectrometry (SIMS) depth profiling. The authors have developed photolithographic and wet-etching processes for patterning the crossovers which are compatible with these materials. The crossover structures were characterized by resistance and insulator pinhole density as well as by the superconducting properties of the patterned top and bottom YBCO electrodes (critical temperature, T_c, and critical current density, J_c). Using SrTiO₃ as the insulating layer, crossovers were made with good isolation between layers (>100 MΩ) and high J_c even in the top electrode (J_c(76 K)>10⁵ A/cm²)