Varela Madera, Mileidy Esther

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    Efecto Hall en películas delgadas de sesquióxido de vanadio
    (2020-12-11) Varela Madera, Mileidy Esther; Rúa de la Asunción, Armando; College of Arts and Sciences - Sciences; Fernández, Félix E.; Marrero Soto, Pablo J.; Department of Physics; Cedeño Maldonado, José R.
    To study the electrical properties of V2O3 thin films, an automatized setup of a Hall effect measurement system was developed and implemented. To assess the performance of the system, a calibration was made with a standard ITO thin film. To characterize the film’s electrical properties, I-V measurements, resistivity by the Van der Pauw technique, and Hall voltages measurements were made. The electrical properties were studied in two phases. In the first phase, the measurements were taken at room temperature and were compared with the film specification provided by the manufacturer. In the second phase, a temperature-dependent electrical characterization of the standard ITO sample was performed with the aid of a cryostat system at the range of 300 K to 60 K in 20 K steps. From the I-V curves, the behavior for all contact points was verified as ohmic. The normalized resistivity of the ITO revealed that this sample has a metallic behavior from 300 K to 110 K, while under 110 K the ITO behaved as an insulator. The Hall coefficient, density, and majority carrier mobility were quasi-independent of the temperature, exhibiting an electrical behavior characteristic of a metallic material, according to the literature. Once the equipment setup was verified and calibrated, V2O3 thin films deposited on glass (SiO2) and sapphire (Al2O3 C-cut) by reactive DC magnetron sputtering were characterized. Nominal conditions were considered to grow these films. The structural characterization was performed using X-ray diffraction (XRD), morphological characterization by Atomic Force Microscopy (AFM), and electrical characterization by the Van der Pauw technique and Hall effect measurements. Similar measurements as with the standard ITO were performed with the V2O3 thin films. At room temperature, the dominant carrier in V2O3/SiO2 and V2O3/Al2O3 (C-cut) samples were holes, which characterized the material as p-type. The V2O3/Al2O3 (C-cut) sample was analyzed with varying temperatures. I-V measurements from 300 K to 225 K with 25 K intervals showed that all contact points behaved as ohmic. The Hall coefficient at the same temperatures showed little variation and confirmed the material as p-type. The majority carrier density was described by a metallic behavior and its mobility registered very low values, with a behavior independent of temperature.