Tuning the resistive switching properties of TiO2-x films

We study the electrical characteristics of TiO2-x-based resistive switching devices fabricated with different oxygen/argon flow ratio during the oxide thin film sputtering deposition. Upon minute changes in this fabrication parameter, three qualitatively different device characteristics were accessed in the same system, namely, standard bipolar resistive switching, electroforming-free devices, and devices with multi-step breakdown. We propose that small variations in the oxygen/ argon flow ratio result in relevant changes of the oxygen vacancy concentration, which is the key parameter determining the resistive switching behavior. The coexistence of percolative or non-percolative conductive filaments is also discussed. Finally, the hypothesis is verified by means of the temperature dependence of the devices in low resistance state.Fil: Ghenzi, Néstor. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. CIC nanoGUNE; EspañaFil: Rozenberg, M.J.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Université Paris Sud; FranciaFil: Llopis, R.. CIC nanoGUNE; EspañaFil: Levy, Pablo Eduardo. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hueso, Luis E.. Universidad del País Vasco; España. Fundación Vasca para la Ciencia; EspañaFil: Stoliar, Pablo Alberto. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. CIC nanoGUNE; Españ

HfO2 based memory devices with rectifying capabilities

We report on the fabrication and characterization of metal/insulator/metal capacitor like devices, with both rectifying and hysteretic features. Devices are formed by two junctions, Ti/HfO2 and Co/HfO2. Each junction exhibits highly repetitive hysteretic I-V curves with a sharp transition from a high to a low resistance state (3–4 orders of magnitude jump). The opposite transition (from low to high) is induced by polarity reversal. The rectifying non-crossing characteristics of the I-V branches denote their potential use as a multifunctional device, acting as a built-in rectifier and memory cell in a single device. Based on the phenomenological model description by Zazpe et al. [Appl. Phys. Lett. 103, 073114 (2013)], we propose a circuital equivalent representation supported on switchable rectifying junctions. By exploring different electrode connections, we disentangle the role of the bulk transport in HfO2 devices.Fil: Quinteros, Cynthia Paula. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zaspe, R.. CIC nanoGUNE; EspañaFil: Marlasca, F. G.. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; ArgentinaFil: Golmar, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Industrial; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; ArgentinaFil: Casanova, F.. CIC nanoGUNE; España. Fundación Vasca para la Ciencia; EspañaFil: Stoliar, Pablo Alberto. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Centre National de la Recherche Scientifique; Francia. Universite de Nantes; FranciaFil: Hueso, L.. Fundación Vasca para la Ciencia; España. CIC nanoGUNE; EspañaFil: Levy, Pablo Eduardo. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Magnetism and electrode dependant resistive switching in Ca-doped ceramic bismuth ferrite

Here we report on the preparation and structural, magnetic and electrical characterization of BiFeO 3 and Bi 0.9Ca 0.1FeO 3 ceramic multiferroic samples. We suggest that Ca-doping creates oxygen vacancies and destabilizes the BiFeO 3 spiral magnetic structure. We also study resistive switching effects in Bi 0.9Ca 0.1FeO 3 with metallic electrodes, finding that the appearance of the effect is dependant on the fabrication procedure of the metallic electrode. On the basis of these observations, we critically revise some assumptions in currently available models of resistive switching of complex oxides.Fil: Rubi, Diego. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín; ArgentinaFil: Marlasca, F. G.. Comisión Nacional de Energía Atómica; ArgentinaFil: Reinoso, M.. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bonville, P.. No especifíca;Fil: Levy, Pablo Eduardo. Comisión Nacional de Energía Atómica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Exploiting phase separation in monolithic La0.6Ca 0.4MnO3 devices

Devices based on mesas were fabricated from thin films of magnetically phase-separated La0.6Ca0.4MnO3. Low-field magnetoresistance arises because the volume fraction of the ferromagnetic metallic phase is large enough for percolation but small enough to permit magnetic decoupling between each mesa and the underlying track. Magnetic domain walls in the antiparallel mesa-track configuration possess a giant resistance-area product of (3-7) × 10-8 Ωm2. This figure represents an 11 order-of-magnitude improvement with respect to the figure for cobalt.Fil: Granja, Leticia Paula. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Hueso, Luis E.. University of Cambridge; Reino Unido. CIC nanoGUNE Consolider; España. Basque Foundation for Science; EspañaFil: Levy, Pablo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; ArgentinaFil: Mathur, N. D.. University of Cambridge; Reino Unido. CIC nanoGUNE Consolider; España. Basque Foundation for Science; Españ

Resistive switching in ceramic multiferroic Bi 0.9Ca 0.1FeO 3

We report resistive switching effects in polycrystalline samples of the multiferroic Bi 0.9Ca 0.1FeO 3 with silver electrodes. Mössbauer spectroscopy shows that upon Ca-doping the Fe remains in a 3 valence state, suggesting charge compensation through the creation of large amounts of oxygen vacancies. Electrical characterization shows that the oxide/metal resistance can be switched between high and low resistance states by applying voltage pulses. This process was shown to be forming free and a strong relaxation after switching was found. We rationalize our results by considering oxygen vacancies migration to and from the metal-oxide interface, resulting in variations of the Schottky potential barrier height that modulate the interface resistance.Fil: Rubi, Diego. Comisión Nacional de Energía Atómica; ArgentinaFil: Gomez-Marlasca, Fernando. Comisión Nacional de Energía Atómica; ArgentinaFil: Bonville, Pierre. Centre National de la Recherche Scientifique; FranciaFil: Colson, Dorothee. Centre National de la Recherche Scientifique; FranciaFil: Levy, Pablo Eduardo. Comisión Nacional de Energía Atómica. Gerencia del Área Investigaciones y Aplicaciones no Nucleares; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Fear of Appreciation

In recent years the term “fear of floating” has been used to describe exchange rate regimes that, while officially flexible, in practice intervene heavily to avoid sudden or large depreciations. However, the data reveals that in most cases (and increasingly so in the 2000s) intervention has been aimed at limiting appreciations rather than depreciations, often motivated by the neomercantilist view of a depreciated real exchange rate as protection for domestic industries. As a first step to address the broader question of whether this view delivers on its promise, we examine whether this “fear of appreciation” has a positive impact on growth performance in developing economies. We show that depreciated exchange rates indeed lead to higher growth, but that the effect, rather than through import substitution or export booms as argued by the mercantilist view, works largely through the deepening of domestic savings and capital accumulation

Fear of Appreciation

In recent years the term “fear of floating” has been used to describe exchange rate regimes that, while officially flexible, in practice intervene heavily to avoid sudden or large depreciations. However, the data reveals that in most cases (and increasingly so in the 2000s) intervention has been aimed at limiting appreciations rather than depreciations, often motivated by the neomercantilist view of a depreciated real exchange rate as protection for domestic industries. As a first step to address the broader question of whether this view delivers on its promise, we examine whether this “fear of appreciation” has a positive impact on growth performance in developing economies. We show that depreciated exchange rates indeed lead to higher growth, but that the effect, rather than through import substitution or export booms as argued by the mercantilist view, works largely through the deepening of domestic savings and capital accumulation

Modeling of the multilevel conduction characteristics and fatigue profile of Ag/La 1/3 Ca 2/3 MnO 3 /Pt structures using a compact memristive approach

The hysteretic conduction characteristics and fatigue profile of La1/3Ca2/3MnO3 (LCMO)-based memristive devices were investigated. The oxide films were grown by pulsed laser deposition (PLD) and sandwiched between Ag and Pt electrodes. The devices exhibit bipolar resistive switching (RS) effect with well-defined intermediate conduction states that arise from partial SET and RESET events. The current-voltage curves are modeled and simulated using a compact memristive approach. Two equations are considered: one for the electron transport based on the double-diode equation and the other for the memory state of the device driven by the play operator with logistic ridge functions. An expression that accounts for the remnant resistance of the device is obtained after simplifying the model equations in the low-voltage limit. The role played by the power dissipation in the LCMO reset dynamics as well as the asymmetrical reduction of the resistance window caused by long trains of switching pulses are discussed.Fil: Miranda, E.. Universidad Autonoma de Barcelona. Facultad de Física; EspañaFil: Roman Acevedo, Wilson Stibens. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes. Gerencia de Investigación y Aplicaciones; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rubi, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes. Gerencia de Investigación y Aplicaciones; ArgentinaFil: Lüders, U.. Centre National de la Recherche Scientifique; Francia. École Nationale Supérieure d'Ingénieurs de Caen; FranciaFil: Granell, Pablo Nicolás. Instituto Nacional de Tecnología Industrial. Centro de Micro y Nanoelectrónica del Bicentenario; ArgentinaFil: Suñé, J.. Universidad Autonoma de Barcelona. Facultad de Física; EspañaFil: Levy, Pablo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Constituyentes. Gerencia de Investigación y Aplicaciones; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología; Argentin

Currency substitution, portfolio diversification and money demand

We extend the Thomas (1985) dynamic optimising model of money demand and currency substitution to the case in which the individual has restricted or no access to foreign currency denominated bonds. In this case Currency Substitution decisions and Asset Substitution decisions are not separable. The results obtained suggest that the significance of an expected exchange rate depreciation term in the demand for domestic money provides a valid test for the presence of currency substitution. Applying this approach to six Latin American countries, we find evidence of currency substitution in Colombia, Dominican Republic and Venezuela, but not in Brazil and Chile

The 2023 wearable photoplethysmography roadmap

Photoplethysmography is a key sensing technology which is used in wearable devices such as smartwatches and fitness trackers. Currently, photoplethysmography sensors are used to monitor physiological parameters including heart rate and heart rhythm, and to track activities like sleep and exercise. Yet, wearable photoplethysmography has potential to provide much more information on health and wellbeing, which could inform clinical decision making. This Roadmap outlines directions for research and development to realise the full potential of wearable photoplethysmography. Experts discuss key topics within the areas of sensor design, signal processing, clinical applications, and research directions. Their perspectives provide valuable guidance to researchers developing wearable photoplethysmography technology