Structure and Properties of Functional Oxide Thin Films: Insights From Electronic‐Structure Calculations

Abstract

The confluence of state-of-the-art electronic-structure computations and modern synthetic materials growth techniques is proving indispensable in the search for and discovery of new functionalities in oxide thin films and heterostructures. Here, we review the recent contributions of electronic-structure calculations to predicting, understanding, and discovering new materials physics in thin-film perovskite oxides. We show that such calculations can accurately predict both structure and properties in advance of film synthesis, thereby guiding the search for materials combinations with specific targeted functionalities. In addition, because they can isolate and decouple the effects of various parameters which unavoidably occur simultaneously in an experiment-such as epitaxial strain, interfacial chemistry and defect profiles-they are able to provide new fundamental knowledge about the underlying physics. We conclude by outlining the limitations of current computational techniques, as well as some important open questions that we hope will motivate further methodological developments in the field.

Ultrahigh‐Power Pseudocapacitors Based on Ordered Porous Heterostructures of Electron‐Correlated Oxides

“…Furthermore, the Raman spectra of the annealed and pristine electrodes retain the same in the feature range from 100 cm −1 to 750 cm −1 , showing no crystalline structure changes during the annealing process. The compelling evidence of V—O—Mn interface structure is further elucidated by density functional theory (DFT) calculations on a periodic supercell of corundum V 2 O 3 (0001)/spinel MnO 2 (111) multilayer 47. The Hirshfeld charge state of the interfacial V atoms increases to ≈0.500 e from ≈0.330 e of the bare V 2 O 3 (Figure S6, Supporting Information), implying that the chemical state of partial V atoms at the V 2 O 3 /MnO 2 interface changes from V 3+ to V 4+ , as shown in the V 2p XPS spectrum with their characteristic peaks of V 2p 1/2 and 2p 3/2 at the binding energies of 522.8, 523.9, 515.5, and 516.6 eV, respectively (Figure S5d, Supporting Information) 48, 49.…”

Crystal structure and electronic properties of bulk and thin film brownmillerite oxides

“…Although there are 15 distinct ways in which the octahedra can cooperatively rotate while retaining connectivity (as identified by Glazer), 46 the vast majority exhibit either an orthorhombic or rhombohedral tilt pattern (given by a − a − c + or a − a − a − in Glazer notation, respectively). A high degree of control over the electronic structure can be achieved by using epitaxial strain (or chemical substation, as captured by τ ) to control these rotations, owing primarily to the strong coupling between the lattice and electronic degrees of freedom in perovskites ( Figure 9a); [47][48][49][50] as mentioned previously, buckling of the B-O-B bond away from a linear 180 • configuration (i.e., increasing the magnitude of the octahedral rotations) decreases the overlap between the O p and metal B d orbitals, thereby increasing the band gap in insulating compounds or inducing bandwidth-driven metal-insulator transitions. [51][52][53][54][55][56] As we have shown, the distinct alternating tetrahedral and octahedral layers in brownmillerites allow for many more structural degrees of freedom than perovskites.…”

Polar octahedral rotations: A path to new multifunctional materials

“…These are materials that are simultaneously magnetic and ferroelectric but the polarization (magnetization) can be manipulated in a useful way with an applied magnetic (electric) field. We know that octahedral rotations can significantly affect the magnetic properties of perovskites, but rotations (or combinations of rotations) in simple perovskites do not directly couple to an external field (other than pressure [14] or stress [15]). In this article, we review progress on a recent development in which the layering of nominally nonpolar perovskites leads to a new type of ferroelectricity in which octahedral rotations induce an electrical polarization.…”