Colored semi-transparent Cu-Si oxide thin films prepared by magnetron sputtering

Colored semi-transparent Cu-Si oxide thin films have been prepared by reactive magnetron sputtering from a single cathode of copper-silicon composition. Thin films of different composition and optical response were obtained by changing process parameters like the relative amount of copper in the target and the O2/Ar mixture of the reactive plasma gas. The film characteristics were analyzed by several techniques. Their optical properties (refractive index, absorption coefficient, color) have been correlated with the process parameters used in the film preparation as well as with the film stoichiometry and chemistry.Ministerio de Ciencia e Innovación CEN-20072014, MAT2010-18447, MAT2010-21228, CSD2008–00023Junta de Andalucía P09-TEP5283, CTS-518

Photoelectrochemical water splitting with ITO/WO3/BiVO4/CoPi multishell nanotubes fabricated by soft-templating in vacuum

A well-established procedure for the photoelectrochemical (PEC) splitting of water relies on using porous electrodes of WO3 sensitized with BiVO4 as a visible scavenger photoanode semiconductor. In this work, we propose an evolved photoelectrode fabricated by a soft-template approach consisting of supported multishell nanotubes (NTs). These NTs are formed by a concentric layered structure of indium tin oxide (ITO), WO3, and BiVO4, together with a final film of cobalt phosphate (CoPi) co-catalyst. Photoelectrode manufacturing is easily implemented at large scale and combines thermal evaporation of single crystalline organic nanowires (ONWs), magnetron sputtering (for ITO and WO3), solution dripping, and electrochemical deposition processes (for BiVO4 and CoPi, respectively) plus annealing under mild conditions. The obtained NT electrodes depict a large electrochemically active surface and outperform by more than one order of magnitude the efficiency of equivalent planar-layered electrodes. A thorough electrochemical analysis of the electrodes under blue and solar light illumination demonstrates the critical role of the WO3/BiVO4 Schottky barrier heterojunction in the control of the NT electrode efficiency and its dependence on the BiVO4 outer layer thickness. Oxygen evolution reaction (OER) performance was maximized with the CoPi electrocatalyst, rendering high photocurrents under one sun illumination. The reported results demonstrate the potential of the soft-template methodology for the large area fabrication of highly efficient multishell ITO/WO3/BiVO4/CoPi NT electrodes, or other alternative combinations, for the photoelectrochemical splitting of water.Comment: Manuscript: 39 pages, 8 figures and 1 table. SI: 15 pages, 9 figures and 1 tabl

Portable IR dye laser optofluidic microresonator as a temperature and chemical sensor

A compact and portable optofluidic microresonator has been fabricated and characterized. It is based on a Fabry-Perot microcavity consisting essentially of two tailored dichroic Bragg mirrors prepared by reactive magnetron sputtering deposition. The microresonator has been filled with an ethanol solution of Nile-Blue dye. Infrared laser emission has been measured with a pump threshold as low as 0.12 MW/cm2 and an external energy conversion efficiency of 41%. The application of the device as a temperature and a chemical sensor is demonstrated. Small temperature variations as well as small amount of water concentrations in the liquid laser medium are detected as a shift of the resonant laser modes.España Mineco MAT2013-40852-R MAT2013-46649-C4-4-PMALTA CSD2007-0045FUNCOAT MAT2015-69035-REDCEU-FEDER P12- FQM-2265 P10-FQM-690

On the microstructure of thin films grown by an isotropically directed deposition flux

The influence of isotropically directed deposition flux on the formation of the thin film microstructure at low temperatures is studied. For this purpose we have deposited TiO2 thin films by two different deposition techniques: reactive magnetron sputtering, in two different experimental configurations, and plasma enhanced chemical vapor deposition. The obtained results indicate that films grown under conditions where deposition particles do not possess a clear directionality, and in the absence of a relevant plasma/film interaction, present similar refractive indices no matter the deposition technique employed. The film morphology is also similar and consists of a granular surface topography and a columnarlike structure in the bulk whose diameter increases almost linearly with the film thickness. The deposition has been simulated by means of a Monte Carlo model, taking into account the main processes during growth. The agreement between simulations and experimental results indicates that the obtained microstructures are a consequence of the incorporation of low-energy, isotropically directed, deposition particles.Ministerio de Ciencia e Innovación MAT 2007- 65764, 2010-CSD2008-00023, PIE 200960I132Junta de Andalucía TEP2275, P07-FQM-0329

Chemistry and Electrocatalytic Activity of Nanostructured Nickel Electrodes for Water Electrolysis

Herein we have developed nanostructured nickel-based electrode films for anion exchange membrane water electrolysis (AEMWE). The electrodes were prepared by magnetron sputtering (MS) in an oblique angle configuration and under various conditions aimed at preparing metallic, oxide, or oxyhydroxide films. Their electrochemical analysis has been complemented with a thorough physicochemical characterization to determine the effect of microstructure, chemical state, bilayer structure, and film thickness on the oxygen evolution reaction (OER). The maximum electrocatalytic activity was found for the metallic electrode, where analysis by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) demonstrated that the active catalytic phase at the surface after its electrochemical conditioning is a kind of oxidized nickel oxide/hydroxide layer with the thickness of a few nanometers. Electrochemical impedance spectroscopy analysis of these steady-state working electrodes supports that the enhanced performance of the metallic nickel anode vs other chemical states resides in the easier electron transfer through the electrode films and the various interlayers built up during their fabrication and activation. The long-term steady-state operation of the anodes and their efficiency for water splitting was proved in a full-cell AEMWE setup incorporating magnetron-sputtered metallic nickel as the cathode. This work proves that MS is a suitable technique to prepare active, stable, and low-cost electrodes for AEMWE and the capacity of this technique to control the chemical state of the electrocatalytically active layers involved in the OER.En este documento, hemos desarrollado películas de electrodos nanoestructuradas a base de níquel para electrólisis de agua con membrana de intercambio aniónico (AEMWE). Los electrodos se prepararon por pulverización catódica con magnetrón (MS) en una configuración de ángulo oblicuo y en diversas condiciones destinadas a preparar películas metálicas, de óxido u oxihidróxido. Su análisis electroquímico se ha complementado con una caracterización fisicoquímica exhaustiva para determinar el efecto de la microestructura, el estado químico, la estructura bicapa y el espesor de la película en la reacción de evolución de oxígeno (OER). La máxima actividad electrocatalítica se encontró para el electrodo metálico, donde el análisis por espectroscopía de fotoelectrones de rayos X (XPS) y espectroscopía de absorción de rayos X (XAS) demostró que la fase catalítica activa en la superficie después de su acondicionamiento electroquímico es una especie de capa de óxido/hidróxido de níquel oxidado con un espesor de unos pocos nanómetros . El análisis de espectroscopía de impedancia electroquímica de estos electrodos de trabajo en estado estacionario respalda que el rendimiento mejorado del ánodo de níquel metálico frente a otros estados químicos reside en la transferencia de electrones más fácil a través de las películas de electrodos y las diversas capas intermedias acumuladas durante su fabricación y activación. La operación de estado estacionario a largo plazo de los ánodos y su eficiencia para dividir el agua se demostró en una configuración AEMWE de celda completa que incorporaba níquel metálico pulverizado con magnetrón como cátodo

CuxCo3-xO4 ultra-thin film as efficient anodic catalysts for anion exchange membrane water electrolysers

CuxCo3-xO4 ultra-thin films, deposited by magnetron sputtering at oblique angles have been used as anodic catalysts in anion exchange membrane water electrolysers. It has been demonstrated that the used deposition procedure provides porous and amorphous samples with a strict control of the total catalyst load and Co/Cu ratio. Electrocatalytic tests showed a maximum performance for the oxygen evolution reaction at Co/Cu atomic ratio around 1.8. The optimized anodic catalyst presented a long-term stability confirmed by accelerated lifetime tests together with the chemical surface analysis of the used samples. The effect of the crystallization of a single layer CuxCo3-xO4 and a multilayer (CuO/Co3O4)n anodic catalyst samples was also investigated. The observed loss of catalytic performance found in both cases may prove that a particular local chemical environment around the Co and Cu sites acts as an efficient catalytic site for the oxygen evolution reaction. A catalyst film with the optimum Co/Cu atomic ratio was incorporated into a Membrane Electrode Assembly, using a sputtered Ni film as cathode. Current density values up to 100 mA cm−2 at 2.0 V were obtained in 1.0 M KOH electrolyte. Upon normalization by the amount of catalyst, this performance is one of the highest reported in literature.Las películas ultrafinas de Cu x Co 3-x O 4 , depositadas por pulverización catódica con magnetrón en ángulos oblicuos, se han utilizado como catalizadores anódicos en electrolizadores de agua con membranas de intercambio aniónico . Se ha demostrado que el procedimiento de deposición utilizado proporciona muestras porosas y amorfas con un estricto control de la carga total de catalizador y la relación Co/Cu. Las pruebas electrocatalíticas mostraron un rendimiento máximo para la reacción de evolución de oxígeno.a una relación atómica Co/Cu alrededor de 1,8. El catalizador anódico optimizado presentó una estabilidad a largo plazo confirmada por pruebas aceleradas de vida útil junto con el análisis químico de superficie de las muestras utilizadas. También se investigó el efecto de la cristalización de una sola capa de Cu x Co 3-x O 4 y una multicapa (CuO/Co 3 O 4 ) en muestras de catalizador anódico . La pérdida observada de rendimiento catalítico encontrada en ambos casos puede probar que un entorno químico local particular alrededor de los sitios de Co y Cu actúa como un sitio catalítico eficiente para la reacción de evolución de oxígeno. Se incorporó una película de catalizador con la relación atómica Co/Cu óptima en un conjunto de electrodos de membrana, usando una película de Ni pulverizada como cátodo. Se obtuvieron valores de densidad de corriente de hasta 100 mA cm - 2 a 2,0 V en electrolito KOH 1,0 M. Tras la normalización por la cantidad de catalizador, este rendimiento es uno de los más altos informados en la literatura

Influence of plasma-generated negative oxygen ion impingement on magnetron sputtered amorphous SiO2 thin films during growth at low temperatures

Growth of amorphous SiO2 thin films deposited by reactive magnetron sputtering at low temperatures has been studied under different oxygen partial pressure conditions. Film microstructures varied from coalescent vertical column-like to homogeneous compact microstructures, possessing all similar refractive indexes. A discussion on the process responsible for the different microstructures is carried out focusing on the influence of (i) the surface shadowing mechanism, (ii) the positive ion impingement on the film, and (iii) the negative ion impingement. We conclude that only the trend followed by the latter and, in particular, the impingement of O- ions with kinetic energies between 20 and 200 eV, agrees with the resulting microstructural changes. Overall, it is also demonstrated that there are two main microstructuring regimes in the growth of amorphous SiO2 thin films by magnetron sputtering at low temperatures, controlled by the amount of O2 in the deposition reactor, which stem from the competition between surface shadowing and ion-induced adatom surface mobilityMinisterio de Innovación español-MAT 2007-65764Ministerio de Innovación español (CONSOLIDER INGENIO 2010)-CSD2008-00023Junta de Andalucía-TEP2275, TEP5283, P07-FQM-03298 y P10-FQM-690

Low refractive index SiOF thin films prepared by reactive magnetron sputtering

We have studied low refractive index fluorine doped silica thin films prepared by reactive magnetron sputtering. Two experimental parameters were varied to increase the porosity of the films, the geometry of the deposition process (i.e., the use of glancing angle deposition) and the presence of chemical etching agents (fluorine species) at the plasma discharge during silica film growth. The microstructure, chemistry, optical properties, and porosity of the films have been characterized by scanning electron and atomic force microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV-Vis, and spectroscopic ellipsometry. It is found that either the deposition at glancing angles or the incorporation of CFx species in the plasma discharge during film growth produces a decrease in the refractive index of the deposited silica films. The combined effect of the two experimental approaches further enhances the porosity of the silica films. Finally, the films prepared in a glancing geometry exhibit negative uniaxial birefringence

Anisotropic Resistivity Surfaces Produced in ITO Films by Laser‐Induced Nanoscale Self‐organization

Highly anisotropic resistivity surfaces are produced in indium tin oxide (ITO) films by nanoscale self‐organization upon irradiation with a fs‐laser beam operating at 1030 nm. Anisotropy is caused by the formation of laser‐induced periodic surface structures (LIPSS) extended over cm‐sized regions. Two types of optimized structures are observed. At high fluence, nearly complete ablation at the valleys of the LIPSS and strong ablation at their ridges lead to an insulating structure in the direction transverse to the LIPSS and conductive in the longitudinal one. A strong diminution of In content in the remaining material is then observed, leading to a longitudinal resistivity ρL ≈ 1.0 Ω·cm. At a lower fluence, the material at the LIPSS ridges remains essentially unmodified while partial ablation is observed at the valleys. The structures show a longitudinal conductivity two times higher than the transverse one, and a resistivity similar to that of the pristine ITO film (ρ ≈ 5 × 10−4 Ω·cm). A thorough characterization of these transparent structures is presented and discussed. The compositional changes induced as laser pulses accumulate, condition the LIPSS evolution and thus the result of the structuring process. Strategies to further improve the achieved anisotropic resistivity results are also provided.This research was funded by the Spanish Ministry of Science, Innovation and Universities, the Spanish Research Agency (AEI, Ministry of Research and Innovation), and the European Regional Development Fund (ERDF) (grant numbers TEC2017-82464-R, PID2019-109603RA-I00, and PID2019-110430GB-C21), the “Consejería de Economía y Conocimiento de la Junta de Andalucía” (PAIDI-2020 projects P18-RT-3480 and -6079). The authors also acknowledge the Consejo Superior de Investigaciones Científicas for the “Intramural Project” (201850E057). C.L.-S. acknowledges the funding of the University of Seville through the “VI Plan Propio de Investigación y Transferencia de la US” (VI PPIT-US). M.M.-M. acknowledges the postdoctoral Juan de la Cierva Incorporación grant (IJCI-2017-33317)) of the same ministry. C.F. thanks the support from the European Commission through the Marie Curie Global Fellowship grant number 844977. V.L.-F. thanks the support from European Commission/Junta de Andalucía Talent-Hub Program

Ionomer-Free Nickel-Iron bimetallic electrodes for efficient anion exchange membrane water electrolysis

A bottleneck for the deployment of the Anion Exchange Membrane Water Electrolysis (AEMWE) is the manufacturing of efficient and long lasting anodes and cathodes for the cells. Highly performant bimetallic Ni/Fe catalyst films with various atomic ratios have been prepared by magnetron sputtering in an oblique angle configuration (MS-OAD) and used as anodes for AEMWE. Electrocatalytic experiments in a small three-electrode cell and a thorough analysis of the electrode properties with various physico-chemical characterization techniques have been used to select the nanostructured anode catalyst which, depicting an optimized Ni/Fe ratio, presents the maximum activity for the oxygen evolution reaction. These anode layers are then scale-up for their integration in an AEMWE cell where the influence of assembly conditions and the effect of adding an ionomer to the anodes have been studied. The obtained results have demonstrated the outstanding properties of the fabricated bimetallic films in terms of activity, stability, and operation under ionomer-free conditions. Current density values around 400 and 600 mA cm−2 at 40 °C and 60 °C (2.0 V), respectively, much higher than those obtained with pure Ni, were obtained with an optimized membrane electrode assembly. The high yield obtained with these electrodes gains further relevance when considering that the current yield per unit mass of the anodic active phase catalyst (i.e., 1086 mA mg−1 at 2.0 V and 40 °C) is the highest among equivalent values reported in literature. The possibilities and prospects of the use of bimetallic catalyst films prepared by MS-OAD for AEMWE are discussed.Un cuello de botella para el despliegue de la electrólisis de agua con membrana de intercambio aniónico (AEMWE) es la fabricación de ánodos y cátodos eficientes y duraderos para las celdas. Se prepararon películas catalíticas bimetálicas de Ni/Fe de alto rendimiento con diversas proporciones atómicas mediante pulverización catódica de magnetrón en una configuración de ángulo oblicuo (MS-OAD) y se usaron como ánodos para AEMWE. Se han utilizado experimentos electrocatalíticos en una pequeña celda de tres electrodos y un análisis exhaustivo de las propiedades del electrodo con varias técnicas de caracterización físico-químicas para seleccionar el catalizador de ánodo nanoestructurado que, con una relación Ni/Fe optimizada, presenta la máxima actividad para el oxígeno. reacción de evolución. Estas capas de ánodos luego se escalan para su integración en una celda AEMWE donde se ha estudiado la influencia de las condiciones de ensamblaje y el efecto de agregar un ionómero a los ánodos. Los resultados obtenidos han demostrado las excelentes propiedades de las películas bimetálicas fabricadas en términos de actividad, estabilidad y funcionamiento en condiciones libres de ionómeros. Valores de densidad de corriente en torno a 400 y 600 mA·cm−2 a 40 °C y 60 °C (2,0 V), respectivamente, muy superiores a los obtenidos con Ni puro, se obtuvieron con un conjunto de electrodo de membrana optimizado. El alto rendimiento obtenido con estos electrodos adquiere mayor relevancia si se considera que el rendimiento de corriente por unidad de masa del catalizador de fase activa anódica (es decir, 1086 mA mg −1 a 2,0 V y 40 °C) es el más alto entre los valores equivalentes reportados en la literatura. . Se discuten las posibilidades y perspectivas del uso de películas catalíticas bimetálicas preparadas por MS-OAD para AEMWE