Buffer Layer Selection for the Fabrication of Freestanding Oxide Membranes

Epitaxial films of complex oxides have gained interest due to their wide-ranging physical properties, including high-temperature superconductivity, magnetism, ferroelectricity, and multiferroicity. Conventionally grown single-crystalline oxide thin films are usually bound to their substrates, which imposes constraints on their properties and usage. Therefore, growth techniques have recently been developed that enable lifting-off freestanding complex oxide membranes by wet etching of oxide buffer layers. To achieve the transfer of large-area oxide films, we have systematically studied the transfer of a variety of thin films grown on aluminate and manganite buffer layers. We found that for a chosen material of the freestanding membrane, the choice of required buffer layer typically is not universal. Various materials of oxide membranes were successfully transferred with good quality and up to 3x 2 mm² area with minimal cracking. This work is expected to enable a wide range of oxide films to be transferred in high quality for fundamental studies and applications in oxide electronic devices.