Browsing by Author "Callahan, Daniel L."
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Item Electrostatic adhesion tester for thin film conductors(1999-12-14) Griffin, Alfred J., Jr.; Brotzen, Franz R.; Callahan, Daniel L.; Yang, Haining S.; Rice University; United States Patent and Trademark OfficeA electrostatic adhesion tester for thin film conductors. In one embodiment, a device is provided for testing the adhesion strength of a thin film conductor that has been formed upon a substrate. The device includes an adhesion tester that is primarily comprised of a conducting portion. The conducting portion is applied to the thin film conductor so that it does not physically contact the thin film conductor, but leaves a small space there between. A power supply may further be provided for coupling to either the adhesion tester, the thin film conductor, or both in order to create a potential difference between the conducting portion and the thin film conductor. The potential difference creates an electric field between the conducting portion and the thin film conductor that induces stress in the thin film conductor. A measuring device may also be provided for coupling to the adhesion tester and the thin film conductor in order to measure an electrical parameter of the electric field, which is indicative of the adhesion strength.Item Growth of ferroelectric thin films through metallo-organic decomposition(1992) Balaraman, Suresh; Callahan, Daniel L.The objective of this investigation is to grow films with good electrical and optical properties through the process of metallo-organic decomposition (MOD) and compare them with those made with other processes such as sputtering. Thin lithium niobate and lead zirconium titanate (PZT) films were made. Films were grown on Si(100), Si(111) and sapphire(012). Thin films made via MOD yielded crystalline films with the absence of other phases other than LiNbO$\sb3$. The films were polycrystalline and often randomly oriented. Grain orientation along (104) was observed on Si(100). An attenuation of 2.8 dB/cm was observed on performing optical waveguiding on films grown on sapphire. Capacitance-voltage measurements yielded dielectric constants of about 28-32 for LiNbO$\sb3$ films on Si. The resistivity as measured from current-voltage tests was 10$\sp{12}$ to 10$\sp{13}$. The PZT films were crystalline and no particular grain orientation was found for films grown on silicon. MOD technique was found to yield films with good stoichiometry. (Abstract shortened with permission of author.)Item Photoluminescence of nitrogen-doped zinc selenide by photo-assisted MOCVD(1993) Gillespie, Paul Matthew; Callahan, Daniel L.Zinc selenide is a wide band-gap (2.67 eV) II-VI compound semiconductor with potential use as a blue electro-optic device material. Problems with obtaining suitable p-type conductivity have limited device development. Zinc selenide epitaxial films, doped with nitrogen from NH$\sb3,$ have been grown on gallium arsenide substrates by laser-assisted metal organic chemical vapor deposition (MOCVD). The effect of nitrogen doping was investigated with and without direct surface irradiation incident on the surface from a broad-band light source. Low temperature (8 K) photoluminescence spectroscopy has confirmed the incorporation of nitrogen as a shallow acceptor by the presence of acceptor-bound-excitons and associated donor-acceptor-pair recombination emissions. The MOCVD growth parameters have been optimized based on the presence of characteristic features in the photoluminescence spectra. Growth rate mechanisms have been proposed for both laser-assisted MOCVD and direct-irradiation MOCVD. Simultaneous interaction of the two photo-assisted techniques show that direct irradiation of the surface does not enhance the growth rate under the laser-assisted condition. This confirms that direct surface irradiation growth mechanisms involve the interaction of photo-generated carriers with alkyl groups from the precursors.