Control of the metal-insulator transition in NdNiO3 thin films through the interplay between structural and electronic properties
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 -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 -oriented films to formation of structural defects and stabilization of non-equilibrium 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.