Universal electric-field-driven resistive transition in narrow-gap Mott insulators

One of today's most exciting research frontier and challenge in condensed matter physics is known as Mottronics, whose goal is to incorporate strong correlation effects into the realm of electronics. In fact, taming the Mott insulator-to-metal transition (IMT), which is driven by strong electronic correlation effects, holds the promise of a commutation speed set by a quantum transition, and with negligible power dissipation. In this context, one possible route to control the Mott transition is to electrostatically dope the systems using strong dielectrics, in FET-like devices. Another possibility is through resistive switching, that is, to induce the insulator-to-metal transition by strong electric pulsing. This action brings the correlated system far from equilibrium, rendering the exact treatment of the problem a difficult challenge. Here, we show that existing theoretical predictions of the off-equilibrium manybody problem err by orders of magnitudes, when compared to experiments that we performed on three prototypical narrow gap Mott systems V2-xCrxO3, NiS2-xSex and GaTa4Se8, and which also demonstrate a striking universality of this Mott resistive transition (MRT). We then introduce and numerically study a model based on key theoretically known physical features of the Mott phenomenon in the Hubbard model. We find that our model predictions are in very good agreement with the observed universal MRT and with a non-trivial timedelay electric pulsing experiment, which we also report. Our study demonstrates that the MRT can be associated to a dynamically directed avalanche

Electronic and physico-chemical properties of nanmetric boron delta-doped diamond structures

Heavily boron doped diamond epilayers with thicknesses ranging from 40 to less than 2 nm and buried between nominally undoped thicker layers have been grown in two different reactors. Two types of [100]-oriented single crystal diamond substrates were used after being characterized by X-ray white beam topography. The chemical composition and thickness of these so-called deltadoped structures have been studied by secondary ion mass spectrometry, transmission electron microscopy, and spectroscopic ellipsometry. Temperature-dependent Hall effect and four probe resistivity measurements have been performed on mesa-patterned Hall bars. The temperature dependence of the hole sheet carrier density and mobility has been investigated over a broad temperature range (6K<T<450 K). Depending on the sample, metallic or non-metallic behavior was observed. A hopping conduction mechanism with an anomalous hopping exponent was detected in the non-metallic samples. All metallic delta-doped layers exhibited the same mobility value, around 3.660.8 cm2/Vs, independently of the layer thickness and the substrate type. Comparison with previously published data and theoretical calculations showed that scattering by ionized impurities explained only partially this low common value. None of the delta-layers showed any sign of confinement-induced mobility enhancement, even for thicknesses lower than 2 nm.14 page

New Trends in Beverage Packaging Systems: A Review

New trends in beverage packaging are focusing on the structure modification of packaging materials and the development of new active and/or intelligent systems, which can interact with the product or its environment, improving the conservation of beverages, such as wine, juice or beer, customer acceptability, and food security. In this paper, the main nutritional and organoleptic degradation processes of beverages, such as oxidative degradation or changes in the aromatic profiles, which influence their color and volatile composition are summarized. Finally, the description of the current situation of beverage packaging materials and new possible, emerging strategies to overcome some of the pending issues are discussed

Etude de couches minces déposées par pulvérisation magnétron postionisée pour l'ingénierie de contraintes - cas du MoCr et de nano-canaux de carbone

This work is devoted to the study of ionized magnetron sputtering stress controlled thin films. This technique uses a secondary inductive plasma, created through a RF (13.56 MHz) powered coil, to post-ionize the sputtered species, as shown by the optical emission spectroscopy plasma analysis. Thus, by acting on the argon pressure, on the substrate bias voltage and on the RF power applied to the coil, the ion flux and energy impinging on the substrate, and thus the film properties and microstructure, can be modified. MoCr films - MoCr is a material used for stress-engineered MEMS elaboration - were deposited by this process. Their characterization enabled to underline the relationship between synthesis conditions and film features, concerning texture, crystallite size and microstrain by XRD, concerning film composition by EDX, and concerning mechanical properties by nano-indentation (hardness and Young's modulus, also measured by traction test coupled XRD). Residual stress in the films were estimated by the curvature and sin²y methods, and the good agreement with TEM observations enabled to describe the mechanisms responsible for stress formation in these films, by underlining the relationship between synthesis conditions, microstructure, morphology and stress state. Besides, the stress control by this process was applied to the elaboration and optimization of amorphous carbon nano-channels, created by buckle delamination control of compressive films, using photolitographically patterned substrates as a template.Cette thèse est dédiée à l'étude de couches minces à contraintes contrôlées par pulvérisation magnétron ionisée. Cette technique utilise un plasma secondaire inductif, créé via une spire alimentée en RF (13,56 MHz), pour post-ioniser les espèces pulvérisées, comme le montre l'analyse du plasma par spectroscopie d'émission optique. Ainsi, en agissant sur la pression d'argon, la polarisation du substrat et la puissance RF dans la spire, le flux et l'énergie des ions arrivant sur le substrat peuvent être modifiés, ainsi que les propriétés et la microstructure des films engendrés. Des films de MoCr, matériau utilisé pour la réalisation de MEMS par ingénierie de contraintes, ont été déposés par ce procédé. Leur caractérisation a permis d'établir le lien entre conditions de dépôt et caractéristiques des films, en termes de texture, de taille de cristallites et de microdéformations par DRX, de composition des couches par EDX et de propriétés mécaniques par nano-indentation (dureté et module d'Young, également estimé par DRX en traction). Les contraintes résiduelles des films ont été évaluées par les méthodes de la courbure et du sin²y, et la bonne corrélation avec des observations MET a permis une description des mécanismes responsables des contraintes dans ces films, en établissant le lien entre conditions de synthèse, microstructure, morphologie et état de contraintes. D'autre part, le contrôle des contraintes par ce procédé a été appliqué à l'élaboration et l'optimisation de nano-canaux de carbone amorphe, créés par contrôle des motifs de délamination de films compressifs, en utilisant des substrats comportant des lignes définies par photolithographie comme gabarits

Étude de couches minces déposées par pulvérisation magnétron post-ionisée pour l'ingénierie de contraintes

Cette thèse est dédiée à l étude de couches minces à contraintes contrôlées par pulvérisation magnétron ionisée. Cette technique utilise un plasma secondaire inductif, créé via une spire alimentée en RF (13,56 MHz), pour post-ioniser les espèces pulvérisées, comme le montre l analyse du plasma par spectroscopie d émission optique. Ainsi, en agissant sur la pression d argon, la polarisation du substrat et la puissance RF dans la spire, le flux et l énergie des ions arrivant sur le substrat peuvent être modifiés, ainsi que les propriétés et la microstructure des films engendrés. Des films de MoCr, matériau utilisé pour la réalisation de MEMS par ingénierie de contraintes, ont été déposés par ce procédé. Leur caractérisation a permis d établir le lien entre conditions de dépôt et caractéristiques des films, en termes de texture, de taille de cristallites et de microdéformations par DRX, de composition des couches par EDX et de propriétés mécaniques par nano-indentation (dureté et module d Young, également estimé par DRX en traction). Les contraintes résiduelles des films ont été évaluées par les méthodes de la courbure et du sin , et la bonne corrélation avec des observations MET a permis une description des mécanismes responsables des contraintes dans ces films, en établissant le lien entre conditions de synthèse, microstructure, morphologie et état de contraintes. D autre part, le contrôle des contraintes par ce procédé a été appliqué à l élaboration et l optimisation de nano-canaux de carbone amorphe, créés par contrôle des motifs de délamination de films compressifs, en utilisant des substrats comportant des lignes définies par photolithographie comme gabarits.This work is devoted to the study of ionized magnetron sputtering stress controlled thin films. This technique uses a secondary inductive plasma, created through a RF (13.56 MHz) powered coil, to post-ionize the sputtered species, as shown by the optical emission spectroscopy plasma analysis. Thus, by acting on the argon pressure, on the substrate bias voltage and on the RF power applied to the coil, the ion flux and energy impinging on the substrate, and thus the film properties and microstructure, can be modified. MoCr films - MoCr is a material used for stress-engineered MEMS elaboration - were deposited by this process. Their characterization enabled to underline the relationship between synthesis conditions and film features, concerning texture, crystallite size and microstrain by XRD, concerning film composition by EDX, and concerning mechanical properties by nano-indentation (hardness and Young s modulus, also measured by traction test coupled XRD). Residual stress in the films were estimated by the curvature and sin methods, and the good agreement with TEM observations enabled to describe the mechanisms responsible for stress formation in these films, by underlining the relationship between synthesis conditions, microstructure, morphology and stress state. Besides, the stress control by this process was applied to the elaboration and optimization of amorphous carbon nano-channels, created by buckle delamination control of compressive films, using photolitographically patterned substrates as a template.NANTES-BU Sciences (441092104) / SudocNANTES-BU Technologie (441092105) / SudocSudocFranceF

Relaxation of a Spiking Mott Artificial Neuron

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Control of resistive switching in AM 4 Q 8 narrow gap Mott insulators: A first step towards neuromorphic applications

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Boron incorporation issues in diamond when TMB is used as extreme doping levels

International audienceBoron doped diamond (BDD) is a very promising material for high frequency and high power applications like Field Emission Transistors and Schottky diodes. Such electrical devices are usually composed of stacked highly BDD layers ([B]> 5x 10(20) at.cm(-3)) on doped at low levels ones ([B] 5x 10(20) at.cm(-3)). SIMS analysis enables to identify the existing links between growth conditions ([CH4]/[H-2] and (B/C)(gas) ratios, pressure, temperature) and the boron incorporation into the diamond matrix. We will finally show that, under optimized growth regimes, the metallic-semiconductor transition above 10(21) at.cm(-3) of boron can be routinely achieved

Relaxation of a Spiking Mott Artificial Neuron

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