Competition between V2O3 phases deposited by one-step reactive sputtering process on polycrystalline conducting electrode
Résumé
This comprehensive work investigates a technologically appealing synthesis of V 2 O 3 oxide thin films for electronic applications by the use of direct reactive sputtering with a heavily diluted gas mixture on a conducting platinum electrode. Morphological characterization was performed by Scanning Electron Microscopy, Atomic Force Microscopy , X-Ray Diffraction and X-Ray Reflectometry. Vanadium valence states were investigated by X-Ray Photoelectron Spectroscopy and crystalline phases were checked by X-Ray Grazing Incidence measurements. Low temperature electrical transport characteristics were determined by 2-point probe measurements. Only amorphous V 2 O 3 was found to exist in a mixed-valence phase in the 2 investigated parameter range. Deposition temperatures between 400 °C and 550 °C enable formation of mixtures between crystallographic phases of corundum-and bixbyite-type V 2 O polymorphs. Depending on temperature and sputtering power, morphology and stoichiometry can be tuned to generate four distinct type of electrical transport characteristics. Most promising electrical properties of corundum V 2 O 3 with a resistance ratio of up to four orders of magnitude (during the low temperature insulator-to-metal transition) have been obtained for a moderate sputtering power of 50 W (on a 1" target) at a deposition temperature of 600 °C. Reactive sputtering thus enables direct control of structural and electrical parameters for polycrystalline V 2 O 3 thin film phases on a conducting substrate.
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