Correlated memory resistor in epitaxial NdNiO3 heterostructures with asymmetrical proton concentration

The electronic devices using correlated transition metal oxides are the promising candidates to overcome the limitation of the current electronics due to the rich electronic phases and the extreme sensitivities. Here, we report proton-based resistive switching memory that uses correlated oxides, i.e., epitaxial NdNiO3 heterostructure with asymmetrical concentration of protons (H+) to obtain multilevel states. By designing such metal-NdNiO3-metal device structures with asymmetrical proton concentration, we demonstrate that the correlated oxides exhibit resistive switching by ionic transport of protons at the metal-hydrogenated NdNiO3 (H-NNO) interface. This finding will guide the development of energy-efficient switching devices for non-volatile memory and neuromorphic applications.open1184sciescopu

Influence of tensile-strain-induced oxygen deficiency on metal-insulator transitions in NdNiO3−δ epitaxial thin films

We report direct evidence that oxygen vacancies affect the structural and electrical parameters in tensile-strained NdNiO3-delta epitaxial thin films by elaborately adjusting the amount of oxygen deficiency (delta) with changing growth temperature T-D. The modulation in tensile strain and T-D tended to increase oxygen deficiency (delta) in NdNiO3-delta thin films; this process relieves tensile strain of the thin film by oxygen vacancy incorporation. The oxygen deficiency is directly correlated with unit-cell volume and the metal-insulator transition temperature (T-MI), i.e., resulting in the increase of both unit-cell volume and metal-insulator transition temperature as oxygen vacancies are incorporated. Our study suggests that the intrinsic defect sensitively influences both structural and electronic properties, and provides useful knobs for tailoring correlation-induced properties in complex oxides.1

Non-volatile ferroelectric control of room-temperature electrical transport in perovskite oxide semiconductor La:BaSnO3

Complex oxide heterostructures composed of oxide semiconductor thin films and ferroelectric single crystals have attracted substantial interest due to the electrically switchable channel resistance by the polarization reversal of ferroelectrics. Here we achieve reversible and non-volatile modulation of room-temperature (RT) resistance in epitaxial La-doped BaSnO3 (LBSO) transparent oxide layers by exploiting the ferroelectric field effect of (001)-oriented Pb(Mg1/3Nb2/3)O3PbTiO3 (PMNPT) single-crystal substrates. Using "all-perovskite" heterostructures, the sheet resistance of the LBSO thin films could be reversibly modified upon polarization switching; as a result, the non-volatile sheet resistance was modulated by up to similar to 70% at RT. Such heterostructures that combine materials with dissimilar functionality provide scientific insights into the charge-mediated physics of perovskite stannate systems coupled to ferroelectric polarization, and show technological potential for non-volatile electronic devices based on new transparent oxide semiconductors.11sciescopu

Enhanced Switchable Ferroelectric Photovoltaic Effects in Hexagonal Ferrite Thin Films via Strain Engineering

Ferroelectric photovoltaics (FPVs) are being extensively investigated by virtue of switchable photovoltaic responses and anomalously high photovoltages of ∼104 V. However, FPVs suffer from extremely low photocurrents due to their wide band gaps (Eg). Here, we present a promising FPV based on hexagonal YbFeO3 (h-YbFO) thin-film heterostructure by exploiting its narrow Eg. More importantly, we demonstrate enhanced FPV effects by suitably exploiting the substrate-induced film strain in these h-YbFO-based photovoltaics. A compressive-strained h-YbFO/Pt/MgO heterojunction device shows ∼3 times enhanced photovoltaic efficiency than that of a tensile-strained h-YbFO/Pt/Al2O3 device. We have shown that the enhanced photovoltaic efficiency mainly stems from the enhanced photon absorption over a wide range of the photon energy, coupled with the enhanced polarization under a compressive strain. Density functional theory studies indicate that the compressive strain reduces Eg substantially and enhances the strength of d–d transitions. This study will set a new standard for determining substrates toward thin-film photovoltaics and optoelectronic devices.111sciescopu

Enhanced Switchable Ferroelectric Photovoltaic Effects in Hexagonal Ferrite Thin Films via Strain Engineering

Ferroelectric photovoltaics (FPVs) are being extensively investigated by virtue of switchable photovoltaic responses and anomalously high photovoltages of ∼10⁴ V. However, FPVs suffer from extremely low photocurrents due to their wide band gaps (<i>E</i>_g). Here, we present a promising FPV based on hexagonal YbFeO₃ (h-YbFO) thin-film heterostructure by exploiting its narrow <i>E</i>_g. More importantly, we demonstrate enhanced FPV effects by suitably exploiting the substrate-induced film strain in these h-YbFO-based photovoltaics. A compressive-strained h-YbFO/Pt/MgO heterojunction device shows ∼3 times enhanced photovoltaic efficiency than that of a tensile-strained h-YbFO/Pt/Al₂O₃ device. We have shown that the enhanced photovoltaic efficiency mainly stems from the enhanced photon absorption over a wide range of the photon energy, coupled with the enhanced polarization under a compressive strain. Density functional theory studies indicate that the compressive strain reduces <i>E</i>_g substantially and enhances the strength of d–d transitions. This study will set a new standard for determining substrates toward thin-film photovoltaics and optoelectronic devices