Browsing by Author "Lederman, David"

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    Hydrogen absorption absorption by metallic thin films detected by optical transmittance measurements
    (PERGAMON-ELSEVIER SCIENCE LTD, 2010) Cabrera, A. L.; Avila, J. I.; Lederman, David
    The hydrogen absorption by bilayers of Pd/Nb and Pd/Ti, grown on glass substrates, was studied by measuring changes in optical transmittance and reflectance in the visible range (wavelengths between 400 nm and 1000 nm) of the films at hydrogen pressures between 3.99 x 10(2) and 4.65 x 10(4) Pa. The electrical resistance of the films was also measured during absorption to correlate with the optical data. All the films were grown by a controlled sputtering technique in high vacuum. Pd films ranging in thickness between 4 nm and 45 nm were also characterized when the films were exposed to a hydrogen pressure. The resistance and transmittance of all the Pd samples increased with the uptake of hydrogen until saturation occurred. For Pd/Ti bilayers, fast uptake of hydrogen was deduced from a transmittance increase, indicating hydrogen absorption in the Ti layer. In the case of the Pd/Nb bilayer, a decrease in transmittance was observed, indicating that hydrogen was not absorbed in the Nb layer. The transmittance decrease could be explained by a reduction of Nb native oxide by the hydrogen at the surface. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.
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    Hydrogen absorption by metallic thin films detected by optical transmittance measurements
    (2010) Cabrera, Alejandro Leopoldo; Ávila Osses, Jonathan Israel; Lederman, David
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    Monte Carlo simulations of exchange bias of ferromagnetic thin films on FeF2(110)
    (2004) Lederman, David; Ramírez Leiva, Ricardo; Kiwi Tichauer, Miguel Germán
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    Structural and magnetic properties of epitaxial delafossite CuFeO2 thin films grown by pulsed laser deposition
    (2015) Joshi, Toyanath; Senty, Tess R.; Trappen, Robbyn; Zhou, Jinling; Chen, Song; Ferrari, Piero; Borisov, Pavel; Song, Xueyan; Holcomb, Mikel B.; Bristow, Alan D.; Cabrera, Alejandro L.; Lederman, David
    Growth of pure phase delafossite CuFeO2 thin films on Al2O3 (00.1) substrates by pulsed laser deposition was systematically investigated as a function of growth temperature and oxygen pressure. X-ray diffraction, transmission electron microscopy, Raman scattering, and x-ray absorption spectroscopy confirmed the existence of the delafossite phase. Infrared reflectivity spectra determined a band edge at 1.15 eV, in agreement with the bulk delafossite data. Magnetization measurements on CuFeO2 films demonstrated a phase transition at T-C approximate to 15 +/- 1K, which agrees with the first antiferromagnetic transition at 14K in the bulk CuFeO2. Low temperature magnetic phase is best described by commensurate, weak ferromagnetic spin ordering along the c-axis. (C) 2015 AIP Publishing LLC.