Browsing by Author "Espinoza-Gonzalez, Rodrigo"

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    In-situ hydrogenated V2O5 thin films: Study of the structural dynamics and their behavior as Li-ion batteries cathode
    (2024) Briceno, Mackarena; Villarroel, Roberto; Zambrano-Mera, Dario; Fernandez, Juan; Flores, Marcos; Rojas-Saez, Nicols; Lisoni, Judit; Hevia, Samuel; Espinoza-Gonzalez, Rodrigo
    This investigation focuses on a one-step preparation method to produce hydrogenated V2O5 thin films by controlling the atmosphere of the DC reactive magnetron sputtering process. An increasing hydrogen flux during the film deposition promotes the formation of defects such as oxygen vacancies and hydroxyl sites in the oxide matrix. The hydrogenated samples were tested as cathodes in Li-ion batteries and exhibited lower charge capacities but superior stability to cycling compared to pristine V2O5 film. These results pave the way to prepare hydrogenated transition metal oxide thin films by a simple route without further thermal procedures and affordable conditions.
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    Optical and mechanical properties of Zr-oxide doped TiO2/SiO2 anti-reflective coatings for PV glass covers
    (2022) Zambrano-Mera, Dario F.; Espinoza-Gonzalez, Rodrigo; Villarroel, Roberto; Rosenkranz, Andreas; Carvajal, Nicolas; Pintor-Monroy, Maria I.; Montano-Figueroa, A. Gabriela; Arellano-Jimenez, Maria J.; Quevedo-Lopez, Manuel; Valenzuela, Paulina; Gacitua, William
    Multi-layer systems are frequently used as anti-reflective coatings (ARCs) due to their excellent optical properties. However, these systems suffer from erosive degradation (wear), thus urgently seeking alternative ways to improve their mechanical properties while maintaining their optical response. To tackle this problem, we propose to dope multi-layer TiO2/SiO2 coatings with Zr-oxides to enhance their crystalline structure and density/ compactness, as well as to form Si-Zr-O bonds. We explore the effect of Zr-oxide doping on the microstructure as well as the optical and mechanical properties of multi-layer TiO2/SiO2 coatings with the overall aim to synergistically induce enhanced optical and mechanical properties. Therefore, homogeneous 250 nm thick multi-layer TiO2/SiO2 coatings doped with Zr-oxides (different atomic concentrations) were deposited on glass substrates by magnetron sputtering. Based on our analysis, Zr-doping improves the optical and mechanical properties simultaneously. Among all ARCs, the sample annealed at 400 C and doped with 1 at.-% Zr presented an excellent anti reflective behavior and the best mechanical performance. These characteristics point towards an improved mechanical resistance (outstanding durability) and optical efficiency thus rendering them excellent candidates for the protection of glass covers on solar panels.
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    Structural and photoelectrochemical dynamics of in-situ hydrogenated anatase TiO2 thin films grown by DC reactive magnetron sputtering
    (2023) Villarroel, Roberto; Zambrano-Mera, Dario; Espinoza-Gonzalez, Rodrigo; Paredes-Gil, Katherine; Pantaleone, Stefano; Ballesteros, Luis; Oskam, Gerko; Garcia-Merino, Jose A.; Hevia, Samuel A.; Gonzalez-Moraga, Guillermo
    Hydrogenation has become one of the most used strategies to improve the photoactive properties of titanium dioxide nanomaterials, n-TiO2. In order to obtain more information about the hydrogenated process on anatase TiO2 thin films and the improvement of the photoactivity of this material, we report a study on the structural changes of hydrogenated anatase thin films produced by direct-current reactive magnetron sputtering. In the first stage of the hydrogenation process, the obtained polycrystalline anatase films present an increment of the {0 0 1} facet according to the amount of hydrogen used in the plasma reaction. At higher hydrogen concentrations, amorphous and rutile phases start to appear. The photoactivity of the hydrogenated anatase samples, H:TiO2, presents a redshift of the photoelectrochemical onset and an increase of the reactivity in the UV region. Both results were experimentally and theoretically related to the formation of defects such as oxygen vacancies and TiH/Ti-OH bonds at the surface of the hydrogenated thin films.