Synthesis of freestanding single-crystal perovskite films and heterostructures by etching of sacrificial water-soluble layers

The use of a sacrificial layer of water-soluble Sr3Al2O6 allows the release of freestanding 2D heterostructures and superlattices of epitaxially grown perovskite oxides while preserving their structural and physical properties. The ability to create and manipulate materials in two-dimensional (2D) form has repeatedly had transformative impact on science and technology. In parallel with the exfoliation and stacking of intrinsically layered crystals1,2,3,4,5, atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality6,7,8,9 and emergent phenomena, as seen in perovskite heterostructures10,11,12. However, separation of these layers from the growth substrate has proved challenging, limiting the manipulation capabilities of these heterostructures with respect to exfoliated materials. Here we present a general method to create freestanding perovskite membranes. The key is the epitaxial growth of water-soluble Sr3Al2O6 on perovskite substrates, followed by in situ growth of films and heterostructures. Millimetre-size single-crystalline membranes are produced by etching the Sr3Al2O6 layer in water, providing the opportunity to transfer them to arbitrary substrates and integrate them with heterostructures of semiconductors and layered compounds13,14.