24 research outputs found
Computation of the expansion parameters of femto-waveguides using a two dimensional micro-Raman map and guided modes
No full textThe expansion parameters of a numerical elastic model that simulates femtosecond laser-material interactions are computed. To achieve this, two dimensional micro-Raman mapping, an elastic-optic finite element model,and the experimental intensity profile of the guided modes were used. To complement this data, the Raman deformation potential constants of the lithium niobate A1(TO4) phonon were obtained and compared with those reported in previous works.Fil: Tejerina, Matías Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigaciones Opticas (i); ArgentinaFil: Torchia, Gustavo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Centro de Investigaciones Opticas (i); Argentin
A low-cost mechatronic system for sol-gel spraypyrolysis technique
No full textThis work presents a design of a low-cost spray pyrolysis automatized system which allows to manufacture high quality thin films. In particular, the thermal component of this instrument is modelled in different operation conditions, analyzed, and controlled. Also, different configurations for the whole instrument are analyzed.Fil: Oviedo, Martin. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; ArgentinaFil: Alvira, Fernando Carlos. Universidad Nacional de Quilmes. Departamento de Ciencia y Tecnología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Apaolaza, Agustin. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; ArgentinaFil: Martiarena, Juan Francisco. Universidad Nacional de La Plata. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Tejerina, Matías Rubén. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentin
Hydrostatic-pressure dependence of Raman-active optical phonons in Nd:Mg:LiNbO3
No full textIn this work, we report the frequency variation of Raman phonon modes of a doped Nd:Mg:LiNbO3 crystal under high hydrostatic pressure up to 6.5 GPa. Whereas most of the phonon modes are not affected by doping, showing the same pressure dependence of their frequency as for undoped LiNbO3, there are three exceptions: The A1(TO)2, the A1(TO)3 and the E(TO)4 phonons. These modes exhibit a considerably different pressure coefficient, which is mainly attributed to the influence of Mg ions occupying Nb-sites in the lithium niobate matrix.Fil: Tejerina, Matías Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigaciones Opticas (i); ArgentinaFil: Pereira Da Silva, K.. Universidade Estadual Do Ceara; Brasil. Institut de Ciència de Materials de Barcelona; EspañaFil: Goñi, A. R.. Institut de Ciència de Materials de Barcelona; España. Institució Catalana de Recerca i Estudis Avancats; EspañaFil: Torchia, Gustavo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigaciones Opticas (i); Argentin
Efeitos do solventes na deposição de filmes finos de ZnO por pulverização pirolítica sol-gel
No full textIn this work we analyze the characteristics of the ZnO film made by sol-gel pyrolytic nebulization, in terms of the variation of solvent composition. For this purpose, we present and discuss a characterization using macroscopic images of the films, X-ray diffraction (XRD) and UV-VIS-NIR transmittance spectroscopy. Among the relevant results, increase in the water/ethanol ratio was found to be related to an increase in film thickness. Furthermore, the thickness, coverage area and transparency of the film were also found to be dependent on the solvent composition of the starting solution. This study contributes to the understanding of the relationship between a major growth parameter such as the composition of the starting solution, and the desired characteristics of ZnO films that are relevant for technological applications.En este trabajo, se analizaron las características de películas de ZnO fabricadas con nebulización pirolítica sol-gel, en términos de la variación de la composición del solvente. Para este propósito, se muestra y discute una caracterización usando imágenes macroscópicas de las películas, difracción de rayos X (XRD) y espectroscopía de transmitancia UV-VIS-NIR. Entre los resultados relevantes se obtuvo que el aumento de la relación agua/etanol está relacionado con un aumento en el espesor de los films. Además, se encontró que el espesor, el área de cobertura y la transparencia de las películas también dependían de la composición del solvente de la solución de partida. Este estudio ayuda a comprender la relación entre un parámetro de crecimiento importante, como lo es la composición de la solución de partida y las características deseadas de las películas de ZnO que son importantes para las aplicaciones tecnológicas.Neste trabalho foram analisadas as características do filme de ZnO fabricadas por nebulização pirolítica sol-gel, em termos da variação da composição do solvente. Para tanto, é mostrada e discutida uma caracterização utilizando imagens macroscópicas dos filmes, difração de raios X (XRD) e espectroscopia de transmitância UV-VIS-NIR. Dentre os resultados relevantes, obteve-se que o aumento da relação água/etanol está relacionado ao aumento da espessura dos filmes. Além disso, verificou-se que a espessura, a área de cobertura e a transparência do filme também dependiam da composição do solvente da solução inicial. Este estudo ajuda a compreender a relação entre um importante parâmetro de crescimento, como a composição da solução inicial, e as características desejadas dos filmes de ZnO que são importantes para aplicações tecnológicas
μ-Raman spectroscopy characterization of LiNbO3 femtosecond laser written waveguides
No full textThe following article appeared in Journal of Applied Physics 112.12 (2012): 123108 and may be found at http://scitation.aip.org/content/aip/journal/jap/112/12/10.1063/1.4769869In this paper, we present an iterative method which merges experimental μ-Raman measurements and numerical simulations to describe femtosecond written waveguides in LiNbO3 crystals. This method is based on the deformation potential theory, and uses the finite element method to analyze elastic deformations after femtosecond laser micro-explosions in x-cut Mg:LiNbO3 crystals. The resultant strain and refractive index field after laser interaction were estimated and yielded similar values to those obtained in other works. The LiNbO3 Raman deformation potential constants were also estimated in this work.This work was partially supported by Agencia Nacional de Promoción Científica y Tecnológica (Argentina) under project PICT-2010-2575 and CONICET (Argentina) under project PIP 0394
Nickel-doped zinc oxide thin films made by spray pyrolysis: experimental characterization and theoretical analyses
No full textAbstract A study of ZnO-based ceramic films prepared by the spray-pyrolysis technique is presented. Pure and Ni-doped thin film samples were deposited as a coating on a glass substrate and experimentally characterized using scanning electron and atomic force microscopies, X-ray diffraction, and UV-vis-NIR spectroscopy. The morphologic, crystallographic, and optical properties were analyzed. Structural and electronic properties were compared to predictions obtained from computational calculations based on the density functional theory plus U approach (DFT+U). All these simulations provided additional data that could be used as a reference for material modeling and a better understanding of the experimental results. It was found that spray pyrolysis can be used to produce thin film ceramic samples (~300 nm) with low amounts (<5%) of Ni impurities substitutionally located at the cationic sites of the ZnO wurtzite host structure. The results of this investigation showed that an experimental and theoretical study aided in a better characterization of the thin films, and helped to outline a more robust model of the samples
Fabrication parameters of ZnO jet nebulizer sprayed films: an analysis of morphological, optical and crystalline properties
No full textAbstract This study examines the influence of fabrication parameters on the morphological, optical, and structural characteristics of zinc oxide (ZnO) films prepared using the jet nebulizer spray pyrolysis technique. Specifically, we analyze the impact of the application distance (ranging from 2 to 8 cm), substrate temperature (ranging from 325 to 425 °C), carrier air pressure (ranging from 5 to 15 psi), and the molar percentage of deionized water/ethanol in the precursor solution (ranging from 0 to 25%). Scanning electron microscopy, X-ray diffraction, and optical transmittance spectroscopy are employed for characterization. Under the employed conditions, film thicknesses ranging between 100 and 680 nm, predominantly strong orientation along the 002 crystalline plane, and visible transparency between 70 and 90% are obtained. Additionally, various morphologies are identified and inspected. Particularly, films produced at longer distances, higher temperatures, and using low or moderate water/ethanol ratios exhibit higher visible transparency (90%), a homogeneous morphology devoid of grain overgrowth, and thicknesses up to 200 nm. These features are desirable for photonic and optoelectronic applications, thus motivating further investigations using the employed technique to obtain wider thicknesses while maintaining these target properties. In summary, this work evaluates the feasibility and tunability of producing transparent and homogeneous ZnO films using the low-cost jet nebulizer spray pyrolysis and contributes to the understanding of this growth process
Welfare Programs and Labor Supply in Developing Countries. Experimental Evidence from Latin America
No full textThis paper studies the effect of welfare programs on work incentives and the labor supply of adults in developing countries. The document builds on the experimental evaluations of three programs implemented in rural areas: Mexico’s PROGRESA, Nicaragua’s Red de Protección Social (RPS) and Honduras’ Programa de Asignación Familiar (PRAF). The impact of welfare on labor supply has been widely studied in developed countries, where most recent initiatives attempt to mitigate negative effects on work incentives. The programs under study are conditional cash transfers (CCT), which combine monetary benefits with incentives for curbing child labor and fostering the accumulation of human capital. Unlike their counterparts in developed economies, however, they do not account for potential impacts on the labor supply of adults, and there is little systematic evidence on this aspect despite a wealth of empirical studies on their intended outcomes. Comparable results for the three countries indicate mostly negative but small and non-significant effects of the programs on the employment of adults, no reallocation of labor between agricultural and other sectors, and a reduction in hours worked by adults in eligible households in RPS. Moreover, PROGRESA had a positive effect on beneficiaries’ wages. The programs did not imply major disincentives to work, despite substantial transfers, but they had some effects on local labor markets. This mechanism is related to recent findings on the indirect impact of CCTs on ineligible households, and implies that future evaluation studies and designs should account for the equilibrium effects of the interventions.welfare programs, income support, labor supply, adult work incentives, conditional cash transfers, randomized control trials, developing countries.
