CONICET | Buscador de Institutos y Recursos Humanos

Titanium dioxide has been widely investigated in the last years due to its outstanding physical and chemical properties that turned it into an interesting material for several technological applications such as oxidant gas sensors. Anatase, a crystalline metastable phase of the TiO2 that can be retained in nanocrystalline materials, is an n-type semiconductor characterized by high electron mobility in which the concentration conduction electron is dependent on the surrounding atmosphere. Thus, anatase films as ceramic gas sensors are based on distinct resistance changes in the presences of gasses. An efficient technique to produce thin films due to its high deposition rate and the good adhesion of the coatings is cathodic arc deposition (CAD). The structure of films produced by CAD depends significantly on the substrate temperature during the coating process.In this work TiO2 thin films prepared by CAD on glass substrates were characterized toward its implementation in gas sensors. The films were grown in an oxygen environment (~2 Pa) employing a 100 A continuous arc. They were synthesized at 400 ºC and at room temperature. The films obtained at 400 ºC grew in anatase phase, while films synthesized at room temperature resulted amorphous and were crystallized in anatase phase with a post-annealing at 400 ºC. The crystalline structure of the films was studied by x-ray diffraction in the glancing angle geometry and some peaks were registered with Bragg- Brentano geometry in order to determine the crystallite size, the morphology was observed by atomic force microscopy, and x ray reflectance measurements were also performed to evaluate the density and the thickness. The electrical conductivity was investigated in the temperature range 250~350°C in air varying the pressure from 0.01 to 1 atm. and with CO concentrations of 500 ppm at 1atm.

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