Epitaxial relations betweeninsitusuperconducting YBa2Cu3O7−xthin films and BaTiO3/MgAl2O4/Si substrates

In situ superconducting YBa2Cu3O7−x films with Tc0 up to 87 K and Jc, 77 K up to 6×104 A/cm2 were prepared on Si substrates with MgAl2O4 and BaTiO3 double‐buffer layers. The epitaxial relations between various layers were established by transmission electron microscopy. The MgAl2O4 layer is heavily faulted. The subsequent BaTiO3 layer stops most of the faults, provides a template for the YBa2Cu3O7−x growth, and partially screens off the stress due to different thermal expansion coefficients. The microstructure of the YBa2Cu3O7−x layer is very similar to that of the films deposited directly on SrTiO3, exhibiting a homogeneous heavily faulted single‐crystal‐like structure free from secondary phases and grain boundaries. The slight degradation of the transport properties is attributed to residual thermal stress.