Browsing by Author "Gonzalez-Fuentes, Claudio"

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    Effect of thiol adsorption on the electrical resistance of copper ultrathin films
    (2024) Gray, Gabriel; Marin, Francisca; del Campo, Valeria; Gonzalez-Fuentes, Claudio; Correa-Puerta, Jonathan; Flores, Marcos; Segura, Rodrigo; Haberle, Patricio; Henriquez, Ricardo
    The impact of thiol adsorption on thin copper films, covered with a copper oxide layer, was investigated using electrical resistance measurements at various stages: during film growth, aging, exposure to air, and immersion in thiol solutions. Thin copper films (20 nm) were thermally evaporated, with variations in substrate temperature (RT, 330 and 390 K). Films deposited at 330 K exhibited the smallest percolation thickness and aging rates due to their compact morphology, showcasing lower surface roughness and correlation length. Exposure to air led to the formation of a Cu2O 2 O layer on the film surface. Subsequent immersion in a dodecanethiol solution in ethanol resulted in a resistance increase, ranging from 0.1 % to 0.4 %. This change was dependent on the substrate temperature, with the largest difference observed at 330 K. This observation suggests that samples grown at this temperature exhibited the highest electron-surface scattering. Moreover, by depositing a chromium surfactant layer, the impact of this scattering mechanism was amplified, leading to a resistance increase of up to 1.2 %. Mayadas-Shatzkes theory provided a good description of these resistance changes. The negatively charged S-head of the adsorbed thiols alters the electric field experienced by conduction electrons in the Cu2O/Cu 2 O/Cu interface, modifying the electron-surface scattering.
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    Spontaneous self-assembly of magnetic nanoparticle chains, at the first stage of a gas aggregation source
    (2024) Orellana, Christian; Gonzalez-Fuentes, Claudio; Abellan, Maria; Segura, Rodrigo; Oyazrun, Simon; Acevedo, Cristian; Romero, Christian
    There is an increasing interest in magnetic nanoparticles (MNPs) and self-assembled MNP chains for applications in biomedicine, catalysis, and other technologically relevant applications. In this work, we report the spontaneous self-assembly of MNPs at the top surface of the shield of a magnetron sputter head. The resulting nanostructures consisted of clustered nanoscale chains arranged in highly oriented microfibers, with lengths of micrometer order and diameters ranging from 20 to 600 nm. The intense magnetic field gradient around the sputter magnetron's head is the driving force of the self-assembly process, also trapping species that would otherwise be lost in the carrier gas flow.