Growth of YBa<inf>2</inf>Cu<inf>3</inf>O(7-δ) thin-films - Nucleation, heteroepitaxy and interfaces

A major research effort in high-temperature oxide superconductors is the growth of high-quality thin films. The physical properties of polycrystalline thin films are controlled by their microstructure, which is influenced by the early stages of film growth and the establishment of epitaxy. In this article, the nucleation and heteroepitaxial growth of YBa2Cu3O7-δ thin films is reviewed. Many of the examples illustrating film growth are taken from studies using transmission electron microscopy. The importance of the substrate surface in controlling film growth is discussed, in particular the growth of YBa2Cu3O7-δ films on vicinal MgO surfaces, enabling the formation of highly oriented microstructures on a substrate where there is a large lattice mismatch. In this case, film growth is described as a form of graphoepitaxy, and models are presented to show the mechanism of film growth and also how the lattice misfit can be reduced by small rotations of the YBa2Cu3O7-δ lattice.