Freestanding crystalline YBa2Cu3O7−x heterostructure membranes

We report the synthesis of millimeter-sized freestanding single-crystal $\mathrm{YB}{\mathrm{a}}₂\mathrm{C}{\mathrm{u}}₃{\mathrm{O}}_{7\ensuremath{-}x}$ heterostructure membranes with nanoscale thickness. On a $\mathrm{SrTi}{\mathrm{O}}₃$ substrate, a heteroepitaxial water-soluble sacrificial layer of $\mathrm{S}{\mathrm{r}}₃\mathrm{A}{\mathrm{l}}₂{\mathrm{O}}₆$ followed by an encapsulated $\mathrm{YB}{\mathrm{a}}₂\mathrm{C}{\mathrm{u}}₃{\mathrm{O}}_{7\ensuremath{-}x}$ film is grown by pulsed laser deposition. A freestanding $\mathrm{YB}{\mathrm{a}}₂\mathrm{C}{\mathrm{u}}₃{\mathrm{O}}_{7\ensuremath{-}x}$ heterostructure membrane is obtained by etching the sacrificial layer. Its high crystalline quality is demonstrated via x-ray diffraction, electrical measurements, and scanning transmission electron microscopy.