The electric-field-assisted hydrogenation and corresponding resistance modulation of NdNiO 3 (NNO) thin-film resistors were systematically studied as a function of temperature and dc electric bias. Catalytic Pt electrodes serve as triple-phase boundaries for hydrogen incorporation into a perovskite lattice. A kinetic model describing the relationship between resistance modulation and proton diffusion was proposed by considering the effect of the electric field during hydrogenation. An electric field, in addition to thermal activation, is demonstrated to effectively control the proton distribution along its gradient with an efficiency of ∼22% at 2 × 10 5 V/m. The combination of an electric field and gas-phase annealing is shown to enable the elegant control of the diffusional doping of complex oxides.

Inspired by the discovery of proton-induced resistance switching in perovskite rare-earth nickelate (RNiO3) films, control of a phase transition via proton doping in strongly correlated systems is considered as a paradigm to explore emerging iontronics functions. Nevertheless, the microscopic proton dynamics under an intrinsic factor of RNiO3 films, namely, lattice strain, has not been clarified in detail. Here we systematically demonstrate a tunable proton diffusion within the perovskite lattice by regulating structural strain in NdNiO3 (NNO) films. The quantification of the proton dynamics, as well as the corresponding resistance modulation ratio (R r) and proton diffusion coverage, is found to be significantly sensitive to the strain. Introducing +2.57% in-plane tensile strain into NNO leads to a suppressed proton diffusion, which ultimately results in a fairly small R r of ∼102. In contrast, NNO film with an in-plane compressive strain of −0.03%, of which R r is ∼106, shows a higher degree of proton diffusion. This finding, supported by results of a density functional theory calculation, reveals the role of lattice strain in controlling the proton diffusion in the RNiO3 system and, in a broader context, in designing multifunctional iontronics devices.

The effects of Cr-stoichiometry on the structural, electrical and optical properties of delafossite-type CuCrO 2 thin films are reported. Thin films were grown by pulsed laser deposition on glass and c-sapphire single-crystal substrates, and the effects of increased temperature on the thin film properties were examined. The substrate temperature and oxygen partial pressure were found to be important processing parameters for fabricating delafossite thin films. The electrical properties of the thin films generally improved with increasing substrate temperature. The properties of the thin films depend on the crystallinity. The improvements in crystallinity and electrical conductivity were made by increasing the Cr-deficiency in the CuCr 1−x O 2 system. By optimising processing parameters, the electrical conductivity of a CuCr 1−x O 2 thin film was 8.30 S/cm (x = 0.00) and this increased with the introduction of Cr-deficiency to 21.03 S/cm (x = 0.03) with a mean optical transmittance of 60%. The bandgaps of the thin films ranged from approximately 3.00 to 3.22 eV.