Growth Characteristics and Electronic Properties of Epitaxial NdNiO₃ Thin Films by Atomic Layer Deposition

The transition to next-generation electronics is inevitable and will require innovative architectures and materials functionalities. The multifunctional and often strongly coupled behaviors of transition metal oxides can offer alternative pathways to more energy-efficient devices, such as transistors. Here, we study thin films of NdNiO3 for its potential as a transistor channel switching material owing to the metal–insulator transition it exhibits at ∼200 K in bulk. The thin films exhibit high structural integrity and relevant functional properties when deposited by atomic layer deposition (ALD) under industrial processing conditions, thus providing a viable pathway for device integration. By varying the ratio of binary oxide subcycles, we can precisely obtain the stoichiometric NdNiO3 composition for which the thin films become epitaxial as deposited at 225 °C on SrTiO3(001). Prior to annealing, the specific resistivities at room temperature show a dependence on the out-of-plane lattice parameter, c, with a nonlinear increase from 10–4 to 10–1 Ωcm as c increases. After annealing at 650 °C in air, both the out-of-plane lattice parameters and resistivities converge toward a narrow range (c = 3.789–3.794 Å and 10–4 Ωcm, respectively). X-ray diffraction and reciprocal space mapping reveal that annealing also has the effect of increasing the strain in the thin films; however, they remain partially relaxed from the substrate. A metal–insulator transition takes place at 140 K under cooling and 175 K upon heating back to room temperature.