Fast route to synthesis of free-standing complex oxide membranes using a sacrificial layer method grown by hybrid MBE

Free-standing membranes have gained interest as they overcome the limitations imposed by the use of a rigid substrate, providing new opportunities in the area of twistronics, moiré-tronics, and artificial heterostructure engineering. A sacrificial layer method has been effective in the creation of membranes, where a crystalline layer is selectively etched in solvents, followed by transfer of target film onto a host substrate. However, the commonly used sacrificial layers are difficult to synthesize with regard to the state-of-the-art thin film growth method of molecular beam epitaxy (MBE). In this study, we synthesize SrTiO₃ membranes ranging from tens-to-hundreds of nanometers in thickness using (Ca, Sr, Ba)O system grown by hybrid MBE and compare them with (Ca,Sr)₃Al₂O₆ sacrificial layers. We show fast synthesis of SrTiO₃ membranes with a large lateral size up to 2-inch of developed membranes with minimum cracks and wrinkles. By combining, structural characterization using x-ray diffraction (XRD), atomic force microscopy (AFM), scanning transmission electron microscopy (STEM), we show bulk-like structural properties. And using electrical and optical characterizations, we show bulk-like dielectric response in SrTiO₃ membranes. We discuss the implications of membrane released from the substrate on their physical properties.