  The integration of high-temperature superconducting YBa2Cu3O6+x (YBCO) into
flexible electronic devices has the potential to revolutionize the technology
industry. The effective preparation of high-quality flexible YBCO films
therefore plays a key role in this development. We present a novel approach for
transferring water-sensitive YBCO films onto flexible substrates without any
buffer layer. Freestanding YBCO film on a polydimethylsiloxane substrate is
extracted by etching the Sr3Al2O6 sacrificial layer from the LaAlO3 substrate.
In addition to the obtained freestanding YBCO thin film having a Tc of 89.1 K,
the freestanding YBCO thin films under inward and outward bending conditions
have Tc of 89.6 K and 88.9 K, respectively. A comprehensive characterization
involving multiple experimental techniques including high-resolution
transmission electron microscopy, scanning electron microscopy, Raman and X-ray
Absorption Spectroscopy is conducted to investigate the morphology, structural
and electronic properties of the YBCO film before and after the extraction
process where it shows the preservation of the structural and superconductive
properties of the freestanding YBCO virtually in its pristine state. Further
investigation reveals the formation of a YBCO passivated layer serves as a
protective layer which effectively preserves the inner section of the
freestanding YBCO during the etching process. This work plays a key role in
actualizing the fabrication of flexible oxide thin films and opens up new
possibilities for a diverse range of device applications involving thin-films
and low-dimensional materials.
