Person: Sánchez Santolino, Gabriel
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First Name
Gabriel
Last Name
Sánchez Santolino
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
Area
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10 results
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Item 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 ÁlvaroDeveloping 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.Item Formation of titanium monoxide (001) single-crystalline thin film induced by ion bombardment of titanium dioxide (110)(Nature communications, 2015) Martínez Pabón, María Beatriz; Beltrán Fínez, Juan Ignacio; Sánchez Santolino, Gabriel; Palacio, I.; López Sánchez, Jesús; Rubio Zuazo, J.; Rojo Alaminos, Juan Manuel; Ferrer, P.; Mascaraque Susunaga, Arantzazu; Muñoz, María del Carmen; Varela Del Arco, María; Castro, G. R.; Rodríguez De La Fuente, ÓscarA plethora of technological applications justify why titanium dioxide is probably the most studied oxide, and an optimal exploitation of its properties quite frequently requires a controlled modification of the surface. Low-energy ion bombardment is one of the most extended techniques for this purpose and has been recently used in titanium oxides, among other applications, to favour resistive switching mechanisms or to form transparent conductive layers. Surfaces modified in this way are frequently described as reduced and defective, with a high density of oxygen vacancies. Here we show, at variance with this view, that high ion doses on rutile titanium dioxide (110) induce its transformation into a nanometric and single-crystalline titanium monoxide (001) thin film with rocksalt structure. The discovery of this ability may pave the way to new technical applications of ion bombardment not previously reported, which can be used to fabricate heterostructures and interfaces.- Project number: PIMCD355/23-24
Item Métodos innovativos en la docencia en el ámbito de electromagnetismo usando la herramienta Wooclap(2024) Biskup Zaja, Nevenko; Nemes, Norbert Marcel; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo; Sánchez Santolino, Gabriel; Sefrioui Khamali, Zouhair; Schmidt, Rainer; Varela Del Arco, María; Azcondo Sánchez, M. Teresa; Rivera Calzada, Alberto Carlos; Scimemi, Ignacio; Barbero Velasco, Isabel; Zamora Castro, Victor; Ternero Villar, Isabel; Romero de Paz, Julio Item Thermally assisted tunneling transport in La_(0.7)Ca_(0.3)MnO_(3)/SrTiO_(3):Nb Schottky-like heterojunctions(Physical review B, 2012) Cuéllar Jiménez, Fabian Andrés; Sánchez Santolino, Gabriel; Varela Del Arco, María; Clement, M.; Iborra, E.; Sefrioui, Zouhair; Santamaría Sánchez-Barriga, Jacobo; León Yebra, CarlosWe report on the electrical transport properties of all-oxide La_(0.7)Ca_(0.3)MnO_(3)/SrTiO_(3):Nb heterojunctions with lateral size of just a few micrometers. The use of lithography techniques to pattern manganite pillars ensures perpendicular transport and allows exploration of the microscopic conduction mechanism through the interface. From the analysis of the current-voltage characteristics in the temperature range 20–280 K we find a Schottky-like behavior that can be described by a mechanism of thermally assisted tunneling if a temperature-dependent value of the dielectric permittivity of SrTiO_(3):Nb (NSTO) is considered. We determine the Schottky energy barrier at the interface, qVB = 1.10 ± 0.02 eV, which is found to be temperature independent, and a value of ξ = 17 ± 2 meV for the energy of the Fermi level in NSTO with respect to the bottom of its conduction band.Item Reversible electric-field control of magnetization at oxide interfaces(Nature communications, 2014) Nemes, Norbert Marcel; Sánchez Santolino, Gabriel; Varela Del Arco, María; Sefrioui, Zouhair; León Yebra, Carlos; Santamaría Sánchez-Barriga, JacoboElectric-field control of magnetism has remained a major challenge which would greatly impact data storage technology. Although progress in this direction has been recently achieved, reversible magnetization switching by an electric field requires the assistance of a bias magnetic field. Here we take advantage of the novel electronic phenomena emerging at interfaces between correlated oxides and demonstrate reversible, voltage-driven magnetization switching without magnetic field. Sandwiching a non-superconducting cuprate between two manganese oxide layers, we find a novel form of magnetoelectric coupling arising from the orbital reconstruction at the interface between interfacial Mn spins and localized states in the CuO2 planes. This results in a ferromagnetic coupling between the manganite layers that can be controlled by a voltage. Consequently, magnetic tunnel junctions can be electrically toggled between two magnetization states, and the corresponding spin-dependent resistance states, in the absence of a magnetic field.Item Resonant electron tunnelling assisted by charged domain walls in multiferroic tunnel junctions(Nature Nanotechnology, 2017) Sánchez Santolino, Gabriel; Tornos Castillo, Javier; Hernandez-Martin, David; Beltrán Fínez, Juan Ignacio; Munuera, Carmen; Cabero Piris, Mariona; Perez-Muñoz, Ana; Ricote, Jesús; Mompean, Federico; Garcia-Hernandez, Mar; Sefrioui Khamali, Zouhair; León Yebra, Carlos; Pennycook, Steve, J.; Muñoz, María Carmen; Varela Del Arco, María; Santamaría Sánchez-Barriga, JacoboThe peculiar features of domain walls observed in ferroelectrics make them promising active elements for next-generation non-volatile memories, logic gates and energy-harvesting devices. Although extensive research activity has been devoted recently to making full use of this technological potential, concrete realizations of working nanodevices exploiting these functional properties are yet to be demonstrated. Here, we fabricate a multiferroic tunnel junction based on ferromagnetic La0.7Sr0.3MnO3 electrodes separated by an ultrathin ferroelectric BaTiO3 tunnel barrier, where a head-to-head domain wall is constrained. An electron gas stabilized by oxygen vacancies is confined within the domain wall, displaying discrete quantum-well energy levels. These states assist resonant electron tunnelling processes across the barrier, leading to strong quantum oscillations of the electrical conductance.Item Paving the way to nanoionics: atomic origin of barriers for ionic transport through interfaces(Scientific reports, 2015) Frechero, M. A.; Rocci, Mirko; Sánchez Santolino, Gabriel; Salafranca, Juan; Schmidt, Rainer; Díaz Guillén, M. R.; Durá, O. J.; Rivera Calzada, Alberto Carlos; Varela Del Arco, María; Santamaría Sánchez-Barriga, Jacobo; León Yebra, CarlosThe blocking of ion transport at interfaces strongly limits the performance of electrochemical nanodevices for energy applications. The barrier is believed to arise from space-charge regions generated by mobile ions by analogy to semiconductor junctions. Here we show that something different is at play by studying ion transport in a bicrystal of yttria (9% mol) stabilized zirconia (YSZ), an emblematic oxide ion conductor. Aberration-corrected scanning transmission electron microscopy (STEM) provides structure and composition at atomic resolution, with the sensitivity to directly reveal the oxygen ion profile. We find that Y segregates to the grain boundary at Zr sites, together with a depletion of oxygen that is confined to a small length scale of around 0.5nm. Contrary to the main thesis of the space-charge model, there exists no evidence of a long-range O vacancy depletion layer. Combining ion transport measurements across a single grain boundary by nanoscale electrochemical strain microscopy (ESM), broadband dielectric spectroscopy measurements, and density functional calculations, we show that grain-boundary-induced electronic states act as acceptors, resulting in a negatively charged core. Besides the possible effect of the modified chemical bonding, this negative charge gives rise to an additional barrier for ion transport at the grain boundary.Item 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, JacoboThe 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.Item Characterization of surface metallic states in SrTiO_(3) by means of aberration corrected electron microscopy(Ultramicroscopy, 2013) Sánchez Santolino, Gabriel; Tornos Castillo, Javier; Cuéllar Jiménez, Fabian Andrés; Bruno, Flavio Yair; León Yebra, Carlos; Santamaría Sánchez-Barriga, Jacobo; Pennycook. S; Varela Del Arco, MaríaAn unusual conducting surface state can be produced in SrTiO3 substrates by irradiation with Argon ions from a plasma source, at low energy and high doses. The effects of irradiation are analyzed here by atomic force microscopy (AFM) and aberration corrected scanning transmission electron microscopy (STEM) combined with electron energy loss spectroscopy (EELS). Depth sensitive studies demonstrate the existence of a heavily damaged surface layer and an oxygen vacancy rich layer immediately underneath, both induced during the irradiation process. We find a clear dependence of the Ti oxidation state with the depth, with a very intense Ti3+ component near the surface. Oxygen vacancies act as n-type doping by releasing electrons into the lattice and producing an insulator-to-metal transition, which explains the unusual metallic behavior of these samples.Item Applications of STEM-EELS to complex oxides(Materials Science in Semiconductor Processing, 2017) Gazquez, Jaume; Sánchez Santolino, Gabriel; Biskup Zaja, Nevenko; Roldan, Manuel A.; Cabero Piris, Mariona; Pennycook, Stephen J.; Varela Del Arco, MaríaIn this chapter we will review a few examples of applications of atomic resolution aberration corrected scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) to complex oxide materials. These are most challenging systems where subtle changes in structure or chemistry may result in colossal responses in macroscopic physical behavior. Here, we will review how atomic resolution compositional mapping can be achieved in manganite thin films and single crystals, highlighting the importance of considering artifacts during quantification. Besides, minor changes in near edge fine structure may take place when the crystalline environment, and hence nearest neighbor configuration, is modified. These can also be tracked by atomic resolution EELS, as will be shown through the study of binary Fe oxides. Also, examples regarding the study of distributions of point defects such as 0 vacancies in cobaltite thin films will be discussed. In these materials, a combination of epitaxial strain and defects may promote physical behaviors not present in bulk, such as the stabilization of unexpected spin state superlattices. Last, a study of extended defects such as dislocation lines will be reviewed. In particular, we will show how chemical segregation at dislocation cores in yttria-stabilized zirconia grain boundaries results in the generation of static O vacancies that affect the local electrostatic potential and hence, the macroscopic ionic conduction properties.