Verbel Márquez, Camilo A.

Profile Picture

Filters

2019 - 201912020 - 20241
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    PublicationRestricted
    Deposition and characterization of thin films of vanadium dioxide
    (2019-07-09) Verbel Márquez, Camilo A.; Rúa de la Asunción, Armando J.; College of Arts and Sciences - Sciences; Fernández, Félix E.; Marrero Soto, Pablo J.; Department of Physics; Gutiérrez, Jorge G.
    In this work, thin films of VO2 and V2O3, were deposited on glass (SiO2) and TiO2 (001) substrates, by D.C. magnetron sputtering, in order to study their structural, electrical, optical and morphological properties. In addition, a thermal treatment was performed on these films under pressure and temperature conditions where VO2 is stable, with the purpose of bringing sample composition close to the correct stoichiometry of this compound. In the same manner, transformation of the V2O3 samples into VO2 was tested. A way to reduce the transition temperature of VO2 to room temperature is through the application of strain. An analogy for this is to grow VO2 in RuO2, because RuO2 has a similar structure to that of this vanadium oxide. To study this effect, RuO2 films were grown on SiO2 and TiO2 (001) substrates and the properties mentioned above were studied. In the study of structural properties using the X-ray diffraction technique, characteristic peaks of the monoclinic structure of the M1 phase of VO2 were observed. The formation of the rhombohedral structure of V2O3 and the tetragonal structure of RuO2 was also determined. In RuO2 its epitaxial growth on TiO2 (001) was confirmed. After carrying out the heat treatment of the VO2 films, it was found that diffraction peaks were close to those reported for the bulk material, showing an improvement in their structural properties. In the case of V2O3 films after the heat treatment, characteristic peaks of the M1 phase of VO2 were found which confirm that there was an oxidation of V2O3 to VO2. The morphology of the films was studied by atomic force microscopy. It was observed that VO2 and V2O3 films showed a slight increase in grain size and a relatively smooth surface after heat treatment. The optical properties were studied by the percentage change in transmittance as a function of temperature, using a laser with wavelength in the infrared. The study of electrical properties was carried out using the Van der Pauw technique. Both, in the optical and electrical properties, it was observed that when the VO2 films were deposited under the same nominal conditions they showed differences in their properties. These changes can be attributed to small variations in the material's stoichiometry.
  • Thumbnail Image
    PublicationEmbargo
    Transition-metal oxides for electrical and high frequencies applications
    (2024-07-10) Verbel Márquez, Camilo A.; Rodríguez Solís, Rafael A.; College of Engineering; Rúa de la Asunción, Armando J.; Medina Sánchez, Rafael H.; León Colón, Leyda V.; Department of Electrical and Computer Engineering; Pérez Muñoz, Fernando
    The study focused on investigating the properties of vanadium oxide (V3O5, VO2 and V4O7) thin films deposited via DC magnetron sputtering on SiO2 and SiO2/Si(100) substrates. The research covered structural, electrical, optical, morphological, and mechanical aspects of these materials. Firstly, V3O5 demonstrated intriguing electrical properties, including a phase transition near 420 K with a order of magnitude change in electrical conductivity, studied using the Van der Pauw technique. A planar device of V3O5 exhibited free-electroforming threshold switching and negative differential resistance, possibly due to localized Joule heating effects. Furthermore, Young's modulus of V3O5 was found close to 195 GPa. High-frequency characteristics were determined for the first time in V3O5 in the frequency range from 5 to 35 GHz. The S-parameters showed that the S11 at low temperature was close to -1.5 dB, and the S21 was approximately -50 dB. At high temperature, the S21 to around -40 dB at 35 GHz. For S11 and S22, similar behavior was observed as at low temperature, with a notable change in the Phase of the device. Also, V3O5 was explored in antenna applications, demonstrating frequency-selective behavior at different temperatures. In collaboration with The Australian National University, optical and biometric thermosensitive properties of V3O5 were studied. It revealed that can undergo electrical switching under exposure to different wavelengths, indicating its photoconductive, bolometric properties and suitability for neuromorphic device applications. Lastly, optical properties of V4O7 were investigated using photoinduced ultrafast methods, revealing nonlinear responses in both metallic and insulating phases.