Person:
Sánchez Santolino, Gabriel

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First Name
Gabriel
Last Name
Sánchez Santolino
URI
https://hdl.handle.net/20.500.14352/85624
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
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2020 - 20232
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Author: Varela Del Arco, María × Subject: 538.9 ×

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    Electrolyte gated synaptic transistor based on an ultra-thin film of La0.7Sr0.3MnO3
    (Advanced Electronic Materials, 2023) López Montes, Alejandro; Tornos Castillo, Javier; Peralta, Andrea; Barbero, Isabel; Fernandez Canizares, Francisco; Sánchez Santolino, Gabriel; Varela Del Arco, María; Rivera Calzada, Alberto Carlos; Camarero, Julio; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo; Romera, Miguel; Romera Rabasa, Miguel Álvaro
    Developing electronic devices capable of reproducing synaptic functionality is essential in the context of implementing fast, low-energy consumption neuromorphic computing systems. Hybrid ionic/electronic three-terminal synaptic transistors are promising as efficient artificial synapses since they can process information and learn simultaneously. In this work, an electrolyte-gated synaptic transistor is reported based on an ultra-thin epitaxial La0.7Sr0.3MnO3 (LSMO) film, a half-metallic system close to a metal-insulator transition. The dynamic control of oxygen composition of the manganite ultra-thin film with voltage pulses applied through the gate terminal allows reversible modulation of its electronic properties in a non-volatile manner. The conductance modulation can be finely tuned with the amplitude, duration, and number of gating pulses, providing different alternatives to gradually update the synaptic weights. The transistor implements essential synaptic features such as excitatory postsynaptic potential, paired-pulse facilitation, long-term potentiation/depression of synaptic weights, and spike-time-dependent plasticity. These results constitute an important step toward the development of neuromorphic computing devices leveraging the tunable electronic properties of correlated oxides, and pave the way toward enhancing future device functionalities by exploiting the magnetic (spin) degree of freedom of the half metallic transistor channel.
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    Controlled sign reversal of electroresistance in oxide tunnel junctions by electrochemical-ferroelectric coupling
    (Physical review letters, 2020) Hernández Martín, David; Gallego Toledo, Fernando; Tornos Castillo, Javier; Rouco Gómez, Víctor; Beltrán Fínez, Juan Ignacio; Munuera, C.; Sánchez Manzano, David; Cabero Piris, Mariona; Cuéllar Jiménez, Fabian Andrés; Arias Serna, Diego; Sánchez Santolino, Gabriel; Mompean, F. J.; García Hernández, M.; Rivera Calzada, Alberto Carlos; Pennycook, S. J.; Varela Del Arco, María; Muñoz, María del Carmen; Sefrioui Khamali, Zouhair; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo
    The persistence of ferroelectricity in ultrathin layers relies critically on screening or compensation of polarization charges which otherwise destabilize the ferroelectric state. At surfaces, charged defects play a crucial role in the screening mechanism triggering novel mixed electrochemical-ferroelectric states. At interfaces, however, the coupling between ferroelectric and electrochemical states has remained unexplored. Here, we make use of the dynamic formation of the oxygen vacancy profile in the nanometerthick barrier of a ferroelectric tunnel junction to demonstrate the interplay between electrochemical and ferroelectric degrees of freedom at an oxide interface. We fabricate ferroelectric tunnel junctions with a La_0.7Sr_0.3MnO_3 bottom electrode and BaTiO_3 ferroelectric barrier. We use poling strategies to promote the generation and transport of oxygen vacancies at the metallic top electrode. Generated oxygen vacancies control the stability of the ferroelectric polarization and modify its coercive fields. The ferroelectric polarization, in turn, controls the ionization of oxygen vacancies well above the limits of thermodynamic equilibrium, triggering the build up of a Schottky barrier at the interface which can be turned on and off with ferroelectric switching. This interplay between electronic and electrochemical degrees of freedom yields very large values of the electroresistance (more than 10^6% at low temperatures) and enables a controlled switching between clockwise and counterclockwise switching modes in the same junction (and consequently, a change of the sign of the electroresistance). The strong coupling found between electrochemical and electronic degrees of freedom sheds light on the growing debate between resistive and ferroelectric switching in ferroelectric tunnel junctions, and moreover, can be the source of novel concepts in memory devices and neuromorphie computing.