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

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 crystals(1-5), atomic-scale thin film growth of complex materials has enabled the creation of artificial 2D heterostructures with novel functionality(6-9) and emergent phenomena, as seen in perovskite heterostructures(10-12). 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 compounds's(13,14).