Echeverría-Altamar, Karla

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    Fabricación y caracterización de películas delgadas de sesquióxido de vanadio dopado con cromo
    (2018-12-12) Echeverría-Altamar, Karla; Rúa-de la Asunción, Armando; College of Arts and Sciences - Sciences; Fernández, Félix E.; Marrero Soto, Pablo J.; Department of Physics; Portnoy, Arturo
    Thin V2O3 films were deposited on SiO2 by reactive DC magnetron sputtering. The films deposited under nominally identical conditions exhibited significant differences in electrical characteristics. The samples were post-annealed with equilibrium temperature and oxygen pressure conditions for V2O3 to assure the stoichiometry in the samples. Moreover, V2O3 films doped with chromium, by thermal reduction of films VO2 phase M1 and M2. The samples were grown by pulsed laser deposition. The crystal structure analysis was studied by x-ray diffraction technique. It was identified the characteristic orientations of the rhombic structure for the films of V2O3 with and without chromium. The morphology of the films was studied by atomic force microscopy. The films of V2O3 presented surfaces with roughness and similar grain size before and after heat treatment. In the doped films, there was a decrease in grain size with an increase in Cr concentration. The electrical properties of the thin films were studied by van der Pauw technique in a temperature range from 80 to 300K. Characteristics hysteresis curves were presented of V2O3 before and after heat treatment. It was observed that although the samples were produced under the same conditions, these presented variations in electrical properties. This was attributed to variations of the stoichiometric of material, due to variables in the process that cannot be adequately controlled. When V2O3 is doped with Cr, it presents metal - insulator transitions at high and low temperature. Therefore, at low temperature, the samples have 0% and 2.5% Cr presented metal - insulator transitions at temperatures 180K and 178K respectively. For the studies at high temperatures, the samples with 1.26% y 1.68% Cr, presented transitions at temperatures 438K and 433K, respectively. Therefore, it is confirmed that films of V2O3 doped with chromium present transitions at low and high temperatures as the bulk material.