Littérature scientifique sur le sujet « Dispositifs à transitions métal-Isolant »
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Thèses sur le sujet "Dispositifs à transitions métal-Isolant"
Leroy, Jonathan. « Caractéristiques électriques non-linéaires de la transition isolant-métal du dioxyde de vanadium (VO2) : application à la conception de métamatériaux accordables dans le domaine térahertz ». Limoges, 2013. https://aurore.unilim.fr/theses/nxfile/default/4a7ab1e6-0a6f-43e4-b594-c062f01f45d2/blobholder:0/2013LIMO4018.pdf.
Texte intégralThe research presented in this manuscript focus on studying the non-linear electrical characteristics of the metal-insulator transition (MIT) in vanadium dioxide (VO2) and their applications towards the fabrication of tunable terahertz (THz) metamaterials. The MIT transition in VO2 can be triggered in different ways (thermal, electrical and optical) and is accompanied by different changes in material properties (conductivity, optical and dielectric properties). We studied the electrical non-linearities of the current-voltage (I-V) characteristics of VO2 based devices during the electrically triggering of the MIT transition. This study highlights a percolative-type MIT transition based on a thermal mechanism. Based on these findings, we design, fabricate and characterize tunable THz metamaterials (0. 1 – 1 THz) integrating VO2 films and patterns. The THz frequency response of the hybrid metamaterials is significantly changing as the VO2 material is performing a reversible thermally or electrically-driven MIT. Our research is opening new, interesting concepts towards the THz tunable and active systems and can be easily transposed for realizing active metamaterial-based devices in the infrared and visible optical domains
Delacour, Corentin. « Architecture Design for Analog Oscillatory Neural Networks ». Electronic Thesis or Diss., Université de Montpellier (2022-....), 2023. http://www.theses.fr/2023UMONS069.
Texte intégralDigitalization of society creates important quantities of data that have been increasing at an exponential rate during the past few years. Despite the tremendous technological progress, digital computers have trouble meeting the demand, especially for challenging tasks involving artificial intelligence or optimization problems. The fundamental reason comes from the architecture of digital computers which separates the processor and memory and slows down computations due to undesired data transfers, the so-called von Neumann bottleneck. To avoid unnecessary data movement, various computing paradigms have been proposed that merge processor and memory such as neuromorphic architectures that take inspiration from the brain and physically implement artificial neural networks. Furthermore, rethinking digital operations and using analog physical laws to compute has the potential to accelerate some tasks at a low energy cost.This dissertation aims to explore an energy-efficient physical computing approach based on analog oscillatory neural networks (ONN). In particular, this dissertation unveils (1) the performances of ONN based on vanadium dioxide oscillating neurons with resistive synapses, (2) a novel mixed-signal and scalable ONN architecture that computes in the analog domain and propagates the information digitally, and (3) how ONNs can tackle combinatorial optimization problems whose complexity scale exponentially with the problem size. The dissertation concludes with discussions of some promising future research directions
Sadiq, Mohammad Nikhian. « Conception et développement de dispositifs hyperfréquences à reconfiguration rapide à partir de matériaux à transition isolant-métal (MIT) : application au dioxyde de vanadium (VO2) ». Thesis, Brest, 2019. http://www.theses.fr/2019BRES0109.
Texte intégralThis thesis, conducted at Lab−STICC as part of the ANR MUFRED project, focuses on the study, the design and the development of reconfigurable microwave devices based on vanadium dioxide (a metal-insulator transition material). This multidisciplinary project – from material deposition and study to the design and characterization of RF devices by way of optical control – aims to demonstrate the VO2 performances as a tuning element for fast (about ten nanoseconds) to ultra-fast (about hundred picoseconds) switching.With this aim in mind, this work begins with a characterization of vanadium dioxide as a tuning element before integrating it into reconfigurable RF devices.Thus, the first VO2 based switches, SPST, SP2T and SP4T are designed for control of the metal-insulator transition with an electrical or optical command. These switches are subsequently used in the design of reconfigurable 1-bit (relative phase shift of 0° and − 45°) and 2-bits (relative phase shift of 0°, − 90°, − 180° and − 270°) switched lines True Time Delay phase shifters.Then this study focuses on the proof-of-concept targeted by the MUFRED project, i.e. a reconfigurable phased array antennas based on VO2 switches. The performances of each RF blocks involved in its design are described, presented and analyzed.The first demonstrators carried out make it possible to foresee prospects for improvement in the short and long term
Seidemann, Johanna. « Iontronic - Étude de dispositifs à effet de champ à base des techniques de grilles liquides ioniques ». Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY075/document.
Texte intégralIonic liquids are non-volatile fluids, consisting of cations and anions, which are ionically conducting and electrically insulating and hold very high capacitances. These liquids have the ability to not only to replace solid electrolytes, but to create strongly increased electric fields (>SI{10}{megavoltpercentimetre}) in the so-called electric double layer (EDL) on the electrolyte/channel interface, which leads to the injection of 2D charge carrier densities up to SI{e15}{cm^{-2}}. The remarkably strong gate effect of ionic liquids is diminished in the presence of trapped states and roughness-induced surface disorder, which points out that atomically flat transition metal dichalcogenides of high crystal quality are some of the semiconductors best suited for EDL-gating.We realised EDL-gated field-effect transistors based on multi-walled ce{WS2} nanotubes with operation performance comparable to that of EDL-gated thin flakes of the same material and superior to the performance of backgated ce{WS2} nanotubes. For instance, we observed mobilities of up to SI{80}{squarecentimetrepervoltpersecond} for both p- and n-type charge carriers and our current on-off ratios exceed SI{e5}{} for both polarities. At high electron doping levels, the nanotubes show metallic behaviour down to low temperatures. The use of an electrolyte as topgate dielectric allows the purely electrostatic formation of a pn-junction. We successfully fabricated a light-emitting transistor taking advantage of this utility.The ability of high charge carrier doping suggests an electrostatically induced metal phase or superconductivity in large gap semiconductors. We successfully induced low temperature metallic conduction into intrinsic diamond with hydrogen-terminated surface via field-effect and we observed a gate effect in doped, metallic silicon.Ionic liquids have many advantageous properties, but their applicability suffers from the instability of their liquid body, gate leakage currents and absorption of impurities. An effective way to bypass most of these problems, while keeping the ability of ultra-high charge carrier injection, is the gelation of ionic liquids. We even went one step further and fabricated modified ion gel films with the cations fixed on one surface and the anions able to move freely through the film. With this tool, we realised a novel low-power field-effect diode
Tran, Ngoc Linh. « Mid-Infrared Intersubband Polaritonic Devices ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST001.
Texte intégralIntersubband (ISB) polaritons are the result of the strong light-matter coupling regime between intersubband transitions in doped quantum wells and a microcavity photonic mode. Owing to their bosonic nature, ISB polaritons can be subject to final state stimulated scattering via different mechanism such as polariton-polariton scattering or polariton-phonon scattering. ISB polaritons hold great promises in view of the development of a novel class of laser, which rely on final state stimulated scattering instead of the population inversion in conventional lasers. This thesis is devoted to the development of optoelectronic devices (lasers and modulators) based on ISB polaritons. In this respect, we have developed a metal-metal (MIM) cavity platform with a periodic opening on the top metallic mirror, which can be employed to perform both electrical and optical injection experiments within ISB polaritons.We have demonstrated the formation of ISB polaritons and their immunity to the presence of inhomogeneous broadening. In addition, we have optimized the linewidth of ISB transitions via an epitaxial growth technique known as growth interruption. Using these MIM cavities, we have successfully demonstrated the evidence of polaritons scattering towards a final state via their interaction with longitudinal optical (LO) phonons under resonant injection of coherent light. We have also developed free-space amplitude modulators, which rely on the change of reflectance of the strong coupling regime to which a radio frequency (RF) bias is applied. Finally, we have shown the existence of a new form of excitonic state within the conduction band of doped Quantum Wells. For this demonstration, we have taken advantage of the strong confinement offered by MIM resonator to bind together the repulsive charges of an ionizing transition.frequency range. In the presented work, we have developed a metal-metal cavity platform with a periodic opening on the top metallic mirror, which can be employed to perform both electrical and optical injection experiments. We have shown the formation of ISB polaritons and we have addressed an issue related to polaritons, i.e., the immunity of ISB polaritons to the presence of inhomogeneous broadening in active regions with high doping. In addition, we have optimized the linewidth of ISB transitions via epitaxial growth techniques such as modulation doping and the growth interruption. Using the metal-metal cavity platform, we have successfully demonstrated the optical pumping experiment into a bright polariton state to reveal the evidence of the polariton scattering towards a final state via interaction with the longitudinal optical (LO) phonon. We have also developed free-space amplitude modulators, which rely on the modulation of the strong coupling regime at a high speed via an applied electric field. Lastly, we have experimentally investigated a new type of the strong coupling regime for bound-to-continuum transitions in quantum well. This finding indicated that the strong light-matter coupling can non-perturbatively modify the excitation nature (ionizing), leading to the formation of polariton modes with the bound state nature
Marrache-Kikuchi, Claire. « Effets dimensionnels dans un système désordonné au voisinage des transitions métal-isolant et supraconducteur-isolant ». Phd thesis, Université Paris Sud - Paris XI, 2006. http://tel.archives-ouvertes.fr/tel-00325067.
Texte intégralMarrache-Kikuchi, Claire Akiko. « Effets dimensionnels dans un système désordonné au voisinage des transitions métal-isolant et supraconducteur-isolant ». Paris 11, 2006. https://tel.archives-ouvertes.fr/tel-00325067.
Texte intégralLow temperature transport in disordered conducting materials imply quantum interference, Coulomb repulsion, and superconducting fluctuations. Since 2D is the lower critical dimension for the existence of metallic and superconducting states, we have studied two quantum phase transitions – the Superconductor-to-Insulator Transition (SIT) and the Metal-to-Insulator Transition (MIT) – when the thickness of a disordered system – here a-NbSi – is lowered. The underlying problem is the transition between the different states and the conditions for a 2D metal to exist. We have studied the field and disorder-induced SIT. The principal characteristics we have observed (renormalization, role of the field orientation) are well explained by M. P. A. Fisher's theory. However, we do not find the critical exponents values and a universal resistance at the transition as predicted by this theory. Concerning the MIT, we have decreased the thickness of a metallic system to reach the dimension 2 and an insulating state. In both transitions, the passage to the insulating state clearly shows the existence of dissipative states at zero temperature that are not predicted by conventional theories. We propose an interpretation of all our results that implies the existence of a novel phase in 2D, a Bose Metal, between the superconducting and the metallic states. This new state has been predicted by recent theories. We trace the corresponding phase diagram for the model system NbSi with respect to concentration and film thickness
Akroune, Abdallah. « Transition métal-isolant dans les oxyfluorures V1-x Mx 02-2x F2x (M = Mg, Mn, Co, Ni) : étude des propriétés structurales, magnétiques et électriques ». Aix-Marseille 1, 1988. http://www.theses.fr/1988AIX11173.
Texte intégralVâju, George Cristian. « Transition isolant-métal et supraconductivité induites par pulse électrique dans les isolants de Mott AM4X8 (A=Ga, Ge ; M=V, Ta, Nb ; X=S, Se) ». Nantes, 2008. http://www.theses.fr/2008NANT2028.
Texte intégralThe chalcogenide lacunar spinel family AM4X8 (A = Ga, Ge ; M = V, Ta, Nb ; X = S, Se) is one of the rare examples of Mott insulators that become metallic under pressure, and even superconducting for GaTa4Se8 (TC = 8 K) et GaNb4Se8 (TC = 5. 7 K). During this PhD thesis, a non–volatile insulator to metal transition was obtained on single crystals of these compounds using a external stimuli very different than pressure : the application of electric pulses as short as 100 ns. This transition is reversible using opposite electrical current. In the “metallic like” state, GaTa4Se8 presents a superconducting state with a TC of about 5-7 K. The resistance does however not drop to zero, suggesting a granular superconductivity. This hypothesis is further confirmed by Scanning Tunneling Microscopy studies, showing an electronic phase separation where two types of nanodomains coexist, metallic ones and extremely insulating ones, both immerged into the insulating majority phase. The mechanism of this pulse–induced reversible insulator – metal transition does not seem to be one of those already known in literature. Our results suggest the existence of a electrostrictive coupling that generates a local compression during the pulse application, leading to a bandwidth-change driven Mott transition. This study could be the first experimental evidence of such a phenomenon. The reversibility of the transition opens the way for the application of these materials in non-volatile RRAM memories
Choquet, Christophe. « Etude de la migration ionique dans les structures métal-isolant-silicium ». Lyon, INSA, 1989. http://www.theses.fr/1989ISAL0048.
Texte intégralLivres sur le sujet "Dispositifs à transitions métal-Isolant"
Gunnarsson, Olle. Alkali-doped fullerides : Narrow-based Solids with Unusual Properties. Singapore : World Scientific Pub., 2004.
Trouver le texte intégralGebhard, Florian. The mott metal-insulator transition : Models and methods. New York : Springer, 1997.
Trouver le texte intégralEdwards, P. Metal-Insulator Transitions Revisited. Taylor & Francis Group, 2004.
Trouver le texte intégralEdwards, P. P., et C. N. R. Rao. Metal-Insulator Transitions Revisited. Taylor & Francis Group, 1995.
Trouver le texte intégralEdwards, P., et C. N. R. Rao. The Metal-Nonmetal Transition Revisited. CRC, 1995.
Trouver le texte intégralGunnarsson, Olle. Alkali-Doped Fullerides : Narrow-Band Solids with Unusual Properties. World Scientific Publishing Company, 2004.
Trouver le texte intégral