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Crystal structure, Density functional theory, Electronic properties, Gallium compounds, High resolution transmission electron microscopy, Metal insulator boundaries, Neodymium compounds, Nickel compounds, Scanning electron microscopy, Semiconductor insulator boundaries, Substrates, Thin films, Transition metal oxides, Transition metals, Correlated electron systems, Crystallographic orientations, Electrical transport measurements, High resolution scanning transmission electron microscopies, Metal-to-insulator transitions, Microscopic length scale, Structural and electronic properties, Structure property relationships, Metal insulator transition
Abstract:
Heteroepitaxy offers a new type of control mechanism for the crystal structure, the electronic correlations, and thus the functional properties of transition-metal oxides. Here we combine electrical transport measurements, high-resolution scanning transmission electron microscopy (STEM), and density functional theory (DFT) to investigate the evolution of the metal-to-insulator transition (MIT) in NdNiO3 films as a function of film thickness and NdGaO3 substrate crystallographic orientation. We find that for two different substrate facets, orthorhombic (101) and (011), modifications of the NiO6 octahedral network are key for tuning the transition temperature TMIT over a wide temperature range. A comparison of films of identical thickness reveals that growth on [101]-oriented substrates generally results in a higher TMIT, which can be attributed to an enhanced bond disproportionation as revealed by the DFT+U calculations, and a tendency of [011]-oriented films to formation of structural defects and stabilization of nonequilibrium phases. Our results provide insights into the structure-property relationship of a correlated electron system and its evolution at microscopic length scales and give new perspectives for the epitaxial control of macroscopic phases in metal-oxide heterostructures. © 2021 authors.
