Fabrication and structure analysis of freestanding superconducting YBa2Cu3O7−x membranes

YBa2Cu3O7−x (YBCO) superconducting freestanding membranes are expected to further expand the application scenarios of flexible electronic devices if the key problem of exfoliating the water-sensitive YBCO films from rigid substrates without damage can be solved. In this work, the two prominent features of Sr4Al2O7 (SAOT), ultrafast water solubility and the ability to sustain epitaxial strain, were utilized to reduce the etching of YBCO and improve the film quality. With SAOT as the buffer layer, YBCO flexible membranes measuring 100 mm2 were achieved from epitaxial films on LAO, STO, and LSAT substrates. Characterizations using synchrotron radiation 3D diffraction, soft x-ray absorption spectroscopy, and electrical transport properties verify that the rapid exfoliation prevents elemental and structural changes and preserves the superconductivity of the YBCO membranes. Transmission electron microscopy studies on the resulting YBCO or YBCO-composite membranes reveal microstructural details such as local crystallinity, phase distribution, domain boundaries, and artificial pinning centers. The work sheds light on the fabrication and investigation of flexible water-sensitive materials.