Etude multi-échelle de la transition métal-isolant de films minces du composé V2O3

Abstract : Vanadium oxide V2O3, which is the prototype of strongly correlated electron systems, is isostructural to corundum α-Al2O3 and has a metallic paramagnetic phase at room temperature. Below 150K, a first-order metal-to-insulator transition is observed, and associated to a magnetic and structural transition.
The objective of this thesis consists to grow and to characterize the structural and physical properties of V2O3 thin films, prepared by the pulsed laser deposition technique, on sapphire substrates (0001-Al2O3). The influence of the strains induced by the substrate and the thickness, upon the properties, was particularly studied. To achieve this goal, a multiscale study of the structure and the electronic transport properties was carried out. While preserving the R-3c structure of the bulk compound, it appears that the strains modify strongly the electrical behaviour of V2O3. The results highlight a surprising evolution with a critical thickness of 220Å. Consequently, the incompressible thick films are metallic on the whole range of temperature and the metal-to-insulator transition observed in bulk material is suppressed. On contrary, the very thin films exhibit a metal-to-insulator transition below 150K, as seen in the bulk. Using measurements on microbridges, we shown that a mesoscopic phase separation, can be used to explain the origin of the macroscopic evolution of the resistivity, and also its qualitative thickness-dependence.
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Submitted on : Tuesday, October 14, 2008 - 4:46:47 PM
Last modification on : Tuesday, February 5, 2019 - 12:12:22 PM
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  • HAL Id : tel-00330541, version 1

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Clara Grygiel. Etude multi-échelle de la transition métal-isolant de films minces du composé V2O3. Matériaux. Université de Caen, 2008. Français. ⟨tel-00330541⟩

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