Bulletin of the American Physical Society
Joint Spring 2016 Meeting of the Texas Sections of APS, AAPT, and Zone 13 of the SPS
Volume 61, Number 3
Thursday–Saturday, March 31–April 2 2016; Beaumont, Texas
Session B2: APS Session -Condensed Matter, Material and Surface Science |
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Chair: Cengiz Sen, Lamar University Room: 210 |
Friday, April 1, 2016 10:30AM - 11:06AM |
B2.00001: Active Conducting Oxide Plasmonics and Metasurfaces Invited Speaker: Howard Ho Wai Lee Plasmonic and metasurface structures have been extensively investigated in the last decade, the electromagnetic responses of those structures are usually fixed at the time of fabrication. In addition, current plasmonic and metasurface systems encounter high optical loss due to the electronic transition absorption of metal. In this talk, I will discuss the use of alternative plasmonic materials, i.e., transparent conducting oxides, to actively electrical control the optical properties of plasmonic and metasurface structures for studying new optical physics and advanced applications. This approach combines the advantages of i) the large optical tunability of conducting oxide materials, ii) the field-effect dynamics of MOS transistor, and iii) the high field confinement to achieve tunable plasmonics and metasurfaces. I will present an experimental demonstration of an ultracompact PlasMOStor, a plasmon slot waveguide field-effect modulator based on a conducting oxide active region that can modulate plasmonic signal with high dynamic range (2.71 dB/$\mu $m) and low waveguide loss ($\sim $0.45 dB/$\mu $m). In addition, I will present our recent results on gate-tunable metasurface that enables dynamic electrical control of the phase and amplitude of the light reflected from the metasurface. A phase shift of $\pi $ and \textasciitilde 30{\%} change in the reflectance are achieved by applying 2.5 V gate bias, a basic requirement for electrically tunable beam-steering phased array metasurfaces. [Preview Abstract] |
Friday, April 1, 2016 11:06AM - 11:18AM |
B2.00002: Charge transfer at adsorbate-covered metal surfaces Bogdana Bahrim, Jamie Stafford, Boris Makarenko Much interest has revolved in recent years around the charge transfer at noble metals covered by adsorbates [1-3]. Why study adsorbate--covered surfaces? Surface adsorbates induce strong local perturbations in the electronic structure and potentials in their surroundings. Even at very low coverage, the charge transfer becomes a complex many-body problem, and is strongly affected by adsorbates. Why study noble metals in particular? Cu, Au, and Ag are interesting because the (111) face presents a band gap that extends below the vacuum level at the gamma point. Such a band gap forbids electrons with certain energies to be transferred into the metal along the surface normal. Therefore, on adsorbate-covered noble metal surfaces the charge transfer is dramatically affected, with consequences on various experimental results such as ion fractions obtained during scattering and sputtering experiments. Our studies investigate the electron dynamics at Na/Cu(111), and provide information about the local effects induced by adsorbates. [1] A.K. Kazansky, A.G. Borisov and J.P. Gauyacq, Surface Science 577, 47 (2005) [2] S. Yu, B. Bahrim, B. Makarenko and J.W. Rabalais, Surface Science 606, 1700 (2012) [3] S. Yu, B. Bahrim, B. Makarenko and J.W. Rabalais, Surface Science 636, 13 (2015) [Preview Abstract] |
Friday, April 1, 2016 11:18AM - 11:30AM |
B2.00003: Surface probe measurements of mix conducto Kuo-Yao Lin, Jason Slinker For the past few decades, the research and industrial application of solid state lighting has been very active. Besides widely-used light emitting diodes (LED) and well-known organic light emitting diodes (OLED), considerable research also focuses on light-emitting electrochemical cells (LEECs) due to their great efficiency, high luminance, and long life time from a simple device architecture. Efficient LEEC devices can be fabricated from a single layer of an ionic transition metal complex (iTMC) between two electrodes, considerably simpler than conventional OLEDs. Ruthenium and iridium complexes are two common iTMC materials used for LEEC devices, with iridium complexes yielding higher efficiency devices. The underlying physics of LEEC devices is not fully understood yet, and researchers have proposed both electrodynamic and electrochemical models to interpret LEEC dynamics. Additional measurements need to be done on LEEC devices to collect enough information to support either model. Scanning Kelvin Probe Microscopy (SKPM) of LEEC devices would reveal the surface potential profile and clarify the physics behind LEECs. Only ruthenium iTMC device surface potential profile measurements have been done before. This talk will focus on SKPM of iridium LEECs to study the physics behind the device [Preview Abstract] |
Friday, April 1, 2016 11:30AM - 11:42AM |
B2.00004: Diffusion of Copper through Ti overlayer Britt Long, A Chourasia The Cu/Ti interface has been characterized by x-ray photoelectron spectroscopy and resistivity measurements. Thin films of copper were deposited on titanium substrates by e-beam method. The thickness of the Ti film was kept at 500 {\AA}. The interface was annealed at temperatures of 100, 200, and 300\textdegree C. The Ti 2p and Cu 2p regions were analyzed by XPS. The diffusivity of copper through titanium has been investigated. [Preview Abstract] |
Friday, April 1, 2016 11:42AM - 11:54AM |
B2.00005: Improve the Optical Properties of Yb/Er: NaGdF$_{\mathrm{4}}$ Nanocrystals Lei Lei, Howard Lee Ln$^{\mathrm{3+}}$-doped NaGdF$_{\mathrm{4}}$ UC nanocrystals (NCs) have been widely investigated as bio-imaging and magnetic resonance imaging agents recently. We provide a facile and straightforward strategy to modify the size and uniformity of NaGdF$_{\mathrm{4}}$ NCs \textit{via} alkaline-earth doping for the first time. By increasing of alkaline-earth doping content, the size of NaGdF$_{\mathrm{4}}$ NCs increases gradually, while the size-uniformity is still retained. Importantly, adopting the Ca$^{\mathrm{2+}}$-doped Yb/Er: NaGdF$_{\mathrm{4}}$ NCs as cores, the complete Ca/Yb/Er: NaGdF$_{\mathrm{4}}$@NaYF$_{\mathrm{4}}$ core-shell particles with excellent size-uniformity can be easily achieved. As a result, UC emission intensity of the complete core-shell NCs increases for about 30 times in comparison with that of the cores, owing to the effective surfaces passivation of the Ca$^{\mathrm{2+}}$-doped cores and therefore protection of Er$^{\mathrm{3+}}$ in the cores from the non-radiative decay. To further enhance the upconversion efficiency, we are combining the core-shell NCs and gold NCs into nano-structured optical fiber that provide an unique and novel platform for studying NC UC effects. [Preview Abstract] |
Friday, April 1, 2016 11:54AM - 12:06PM |
B2.00006: Using DNA Devices to Track Anticancer Drug Activity$\backslash $ Dimithree Kahanda, Jason D. Slinker, Marc A. Mcwilliams, Gaurab Chakrabarti, David A. Boothman h $-abstract-$\backslash $pard It is beneficial to develop systems that represent significant complexity of biological systems, while maintaining control over specific factors involved in a particular process. We have established a chip-based electrochemical platform for following the repair of DNA damage produced by a redox-cycling anticancer drug, beta-lapachone ($\beta $-lap). These chips, which possess key features to reproduce the cellular environment, drug cofactors, and base-excision repair (BER) enzymes tracked DNA damage repair activity with redox probe-modified DNA monolayers on gold. The concentration dependence of {\ss}-lap revealed significant square wave signal changes at levels of high clinical significance as well as sensitivity to sub-lethal levels of {\ss}-lap. We also demonstrate high correlation of this change with the specific drug cycle through rational controls. Thus, this chip-based platform enabled tracking of drug-induced damage repair processes when biological criteria were met, providing a unique synthetic platform for uncovering activity normally confined to inside cells.$\backslash $pard-/abstract-$\backslash $\tex [Preview Abstract] |
Friday, April 1, 2016 12:06PM - 12:18PM |
B2.00007: A theoretical study on the pure-phase stability of complex solar absorber materials Muhammad N. Huda, Cedric L. Mayfield, Pranab Sarker To make solar energy competitive with fossil fuels, sustainable and cost effective solar absorber materials are needed. In this regards, we are particularly interested in multi-cation oxide/sulfide materials as they present flexible pathways to tune their electronic and optical properties. Once a material is selected, the primary challenge is to predict whether the material or the material with preferred doping can be synthesized as pure-phase in thermodynamic equilibrium conditions. We will present density functional theory (DFT) studies on two such examples for solar absorber materials: (i) Cu$_{\mathrm{2}}$ZnSnS(Se) (CZTS) and (ii) Bi$_{\mathrm{2}}$Ti$_{\mathrm{2}}$O$_{\mathrm{7}}$ (BTO).$_{\mathrm{\thinspace }}$We'll fist show from the chemical potential landscape analysis that the formation of stoichiometric CZTS is practically impossible under thermodynamic equilibrium condition. Our study justifies the experimental growth conditions of CZTS (Zn rich and Cu-poor) for higher solar-to-current conversion efficiency. Growth condition for p-type CZTS and suitable reaction pathways will be presented. In the second example, a resent experiment showed that a transition metal such as Fe inclusion can enhanced photo-current of bismuth titanate (Bi$_{\mathrm{2}}$Ti$_{\mathrm{2}}$O$_{\mathrm{7}})$ up to an impurity concentration of \textasciitilde 1{\%}. Beyond this impurity concentration the photocurrent decreased due to the formation of Fe$_{\mathrm{2}}$O$_{\mathrm{3}}$ phase. Our theoretical study predicted the doping configurations and suitable chemical potential ranges to avoid formation of the Fe$_{\mathrm{2}}$O$_{\mathrm{3}}$ phase in Fe- doped BTO in order to increase the photo-current. [Preview Abstract] |
Friday, April 1, 2016 12:18PM - 12:30PM |
B2.00008: High Magnetic Field calculations of Molecular Hydrogen Dissociation Jonathan Jerke, Samina Masood, Chris Tymczak The dissociation curves of molecular Hydrogen in a 1 and 10 milli au magnetic field are calculated in a Generalized Hartree Fock theory, GHF.~~In GHF, the electrons are allowed to spin in any direction at each point in space, i.e. torsional spin waves.~~Torsional spin wave magnitude on the atomic cores, as well as the transition from a covalent bond to two doublets, is observed.~~~The vibrational spectra of the ground state is also reported.~~By comparison, based on absolute accuracy of matrix elements and zero field calculations, these calculations of electronic structure achieve 3-4 significant digits on absolute energy in a generalized Hartree Fock calculation. [Preview Abstract] |
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