Browsing by Author "Garcia-Merino, Jose Antonio"

Now showing 1 - 4 of 4
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    A comprehensive study of the nonlinear optical response exhibited by ion-implanted silica plates with Au and Pt nanostructures
    (2021) Hernandez-Acosta, Marco Antonio; Torres-Torres, Carlos; Bornacelli, Jhovani; Garcia-Merino, Jose Antonio; Can-Uc, Bonifacio; Rangel-Rojo, Raul; Oliver, Alicia
    Third -order nonlinear optical properties exhibited by Platinum nanoclusters and Gold nanoparticles integrated in a two -stage configuration are reported. Comparative nanostructures were nucleated in a monolithic complex platform form based on a single matrix by a dual ion -implantation process and a reduction in the ablation threshold from 2.2 J/cm2 to 1.2 J/cm2 was obtained. This modification in the photothermal response exhibited by the nanoparticles seems to derive from a fractional transfer of energy. Femtosecond z -scan measurements at 800 nm revealed a strong two -photon absorption in the dual -implanted sample together to an ultrafast electronic nonlinearity responsible for a self -defocusing effect. These findings highlight the potential for tailoring quantum systems by integration of hybrid photonic circuits using multi -implantation processes.
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    Nickel Nanopillar Arrays Electrodeposited on Silicon Substrates Using Porous Alumina Templates
    (2020) Bejide, Matias; Contreras, Patricio; Homm, Pia; Duran, Boris; Garcia-Merino, Jose Antonio; Rosenkranz, Andreas; Denardin, Juliano C.; del Rio, Rodrigo; Hevia, Samuel A.
    Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications.
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    The Synthesis of Sponge-like V2O5/CNT Hybrid Nanostructures Using Vertically Aligned CNTs as Templates
    (2024) Picuntureo, Matias; Garcia-Merino, Jose Antonio; Villarroel, Roberto; Hevia, Samuel A.
    The fabrication of sponge-like vanadium pentoxide (V2O5) nanostructures using vertically aligned carbon nanotubes (VACNTs) as a template is presented. The VACNTs were grown on silicon substrates by chemical vapor deposition using the Fe/Al bilayer catalyst approach. The V2O5 nanostructures were obtained from the thermal oxidation of metallic vanadium deposited on the VACNTs. Different oxidation temperatures and vanadium thicknesses were used to study the influence of these parameters on the stability of the carbon template and the formation of the V2O5 nanostructures. The morphology of the samples was analyzed by scanning electron microscopy, and the structural characterization was performed by Raman, energy-dispersive X-ray, and X-ray photoelectron spectroscopies. Due to the catalytic properties of V2O5 in the decomposition of carbonaceous materials, it was possible to obtain supported sponge-like structures based on V2O5/CNT composites, in which the CNTs exhibit an increase in their graphitization. The VACNTs can be removed or preserved by modulating the thermal oxidation process and the vanadium thickness.
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    Tunable Low Crystallinity Carbon Nanotubes/Silicon Schottky Junction Arrays and Their Potential Application for Gas Sensing
    (2021) Adrian, Alvaro R.; Cerda, Daniel; Fernandez-Izquierdo, Leunam; Segura, Rodrigo A.; Garcia-Merino, Jose Antonio; Hevia, Samuel A.
    Highly ordered nanostructure arrays have attracted wide attention due to their wide range of applicability, particularly in fabricating devices containing scalable and controllable junctions. In this work, highly ordered carbon nanotube (CNT) arrays grown directly on Si substrates were fabricated, and their electronic transport properties as a function of wall thickness were explored. The CNTs were synthesized by chemical vapor deposition inside porous alumina membranes, previously fabricated on n-type Si substrates. The morphology of the CNTs, controlled by the synthesis parameters, was characterized by electron microscopies and Raman spectroscopy, revealing that CNTs exhibit low crystallinity (LC). A study of conductance as a function of temperature indicated that the dominant electric transport mechanism is the 3D variable range hopping. The electrical transport explored by I-V curves was approached by an equivalent circuit based on a Schottky diode and resistances related to the morphology of the nanotubes. These junction arrays can be applied in several fields, particularly in this work we explored their performance in gas sensing mode and found a fast and reliable resistive response at room temperature in devices containing LC-CNTs with wall thickness between 0.4 nm and 1.1 nm.