Tuning electronic properties in LaNiO3 thin films by B-site Cu-substitution

Abstract

Resistors are essential parts of futuristic all-oxide electronic architectures, yet easily overlooked due to their apparent simplicity. Herein, design of thin films with specific resistance spanning six orders of magnitude by partial substitution of Cu²⁺ for Ni³⁺ in the metallic conductor LaNiO₃ is shown. Substitution is attainable across the whole composition range using atomic layer deposition on LaAlO₃(100)_pc substrates, however with some inclusion of Ruddlesden–Popper RP1 phase (La₂CuO₄) at high levels of Cu-incorporation. The thermal stability of the resistance is based on a metal–insulator transition that evolves from non-existent for LaNiO₃ to above room-temperature for high Cu²⁺ substitution. This provides further insight in the metal–insulator transition found for correlated rare-earth nickelates, especially the type of transition seen for ultrathin films of LaNiO₃ that is usually attributed to oxygen vacancy formation. Materials with variable resistivity and metal–insulator-transition temperatures are key in the design of futuristic electronics such as metal–insulator-transition-driven neuromorphic devices.