Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session Z24: Oxides and other Insulators |
Hide Abstracts |
Sponsoring Units: DCMP Chair: Rickard Armiento, Massachusetts Institute of Technology Room: D133-D134 |
Friday, March 19, 2010 11:15AM - 11:27AM |
Z24.00001: A Synchrotron Investigation Of The Electronic Structure Of Lanthanide Zirconates Richard Clements, Brendan Kennedy, Christopher Ling, Anton P.J. Stampfl abstract- The lanthanide zirconates are of interest for use in inert matrix fuels and nuclear wasteforms. For use in these applications, the material's structure must be resistant to radiation damage and its thermal, thermodynamic and mechanical properties must be known. The rare earth zirconates are interesting model systems to explore such problems. In such materials the f-electrons may play a localized valence decisive role in determining their thermo-mechanical properties. We have undertaken a synthesis of the full range of the lanthanide zirconate series using solid state techniques. We have performed X-ray photoemission spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES) with synchrotron radiation on a selection of the series, in conjunction with a density functional theory (DFT) determination of the electronic structure. - [Preview Abstract] |
Friday, March 19, 2010 11:27AM - 11:39AM |
Z24.00002: A General Mechanism for Negative Capacitance Phenomena Jason Shulman, Yu-Yi Xue, Stephen Tsui, Feng Chen, C.W. Chu Negative capacitance (NC) is a relatively unknown, yet common, phenomenon that is found in a wide variety of materials and devices spanning the major branches of science. The microscopic mechanisms governing NC in these systems are, naturally, as varied as the materials themselves. However, they do share several common features. NC arises in the presence of a \textit{dc} bias, while the materials themselves are nonlinear and possess strong dispersion. The current study focuses on NC in an electrorheological fluid composed of urea coated Ba$_{0.8}$(Rb)$_{0.4}$TiO(C$_{2}$O$_{4})_{2}$ nanoparticles dispersed in silicone oil. The NC of the fluid is plasma-like in nature and related to the nonlinearity of the fluid's conductivity. A general mechanism, describing the NC of the fluid as well as other materials, has been developed by exploiting the common features associated with NC. The mechanism demonstrates that NC arises from \textit{dc}/\textit{ac} signal mixing across a nonlinear conductor. [Preview Abstract] |
Friday, March 19, 2010 11:39AM - 11:51AM |
Z24.00003: Electronic structure and linear response properties of the crystal KIO$_3$: A first-principle density-functional theory study Yiming Mi, Xinxin Zhao, Shuichi Iwata The electronic band structure and both the partial and total density of states of the ABO$_3$ type crystal KIO$_3$ are investigated based on the first principles pseudopotential plane wave approach within density functional theory formalism. The structural optimization was performed in terms of generalized gradient approximation. And the optical properties and the imaginary parts of the frequency-dependent dielectric function of the material are also calculated. The acquired calculational results of the material are in good agreement with available experimental data. [Preview Abstract] |
Friday, March 19, 2010 11:51AM - 12:03PM |
Z24.00004: Experimental Demonstration of Memory Capacitance and Memory Resistance in VO$_{2}$ devices Tom Driscoll, Dimitri Basov, Massimiliano Di Ventra, Hyun-Tak Kim, Byung-Gyu Chae, Nan Jokerst, Sabarni Palit, David Smith Memristors are a special case of non-linear resistors which store information about the history of applied voltage in their instantaneous resistance value. These memory-resistors have attracted considerable attention for their possible uses in information storage and neuromorphic circuits. The same circuit principles behind memory-resistance have been extended to postulate that memory-capacitance and memory-inductance phenomena are also likely to exist$^{1}$. In this talk, we discuss experimental results from a Vanadium-Dioxide device which exhibits memory-capacitance$^{2}$. The nanoscale phase-separation phenomena which underlie this memory-capacitance suggest similar effects may exist in a variety of materials.\\[4pt] [1]. M. Di Ventra et.al. Proc. IEEE 97, 1717 (2009) \newline [2]. T.Driscoll et.al. Science. 325, 1518 (2009) [Preview Abstract] |
Friday, March 19, 2010 12:03PM - 12:15PM |
Z24.00005: First Principles Study on Ta$_{25 }$ Low- and High-Temperature Phases Yu-Ning Wu, Lan Li, Hai-Ping Cheng Low- and high-temperature phases of Tantalum pentoxide (Ta$_{2}$O$_{5})$ have been studied by density functional method. Our calculations have been carried out using the projector-augmented wave method and a plane wave basis set. Tantalum pen-oxide, Ta$_{2}$O$_{5}$ is considered as a potential alternative to SiO$_{2}$ because of its high breakdown voltage, its high dielectric constant, and its excellent step coverage characteristics. It is also a dielectric material for optical coating application that is important to high precision instrumentation. We have studied structure, electronic properties, and phonon spectra, as well as elastic modulii, including bulk modulus, Young's modulus and Poisson's ratio. Four different isomorphs will be presented. Furthermore, SiO$_{2}$-doped Ta$_{2}$O$_{5}$, which is used as mirror coatings in current interferometric gravitational wave detectors, has also been investigated. Our results help to understand the properties of this material in different phases. [Preview Abstract] |
Friday, March 19, 2010 12:15PM - 12:27PM |
Z24.00006: Electronic structure of PbTiO3-based ferroelectric materials determined from LDA+U study Gaoyang Gou, Hiroyuki Takenaka, Joseph Bennett, Andrew Rappe We perform a systematic theoretical study of the electronic structure of PbTiO$_3$ and related ferroelectric materials, using LDA+$U$ calculations. The effective on-site correlation terms $U$ for the localized electronic states of PbTiO$_3$ are determined with a linear-response method. Compared to the DFT- LDA method (where the band gap values are greatly underestimated), band gap values for PbTiO$_3$ obtained by LDA+$U$ calculations are much closer to the experimental results. Special focus has been paid to solid-state solutions formed by doping PbTiO$_3$ with a $d^8$ cation (Ni, Pd, Pt) and accompanying O vacancy, which have recently been proposed. We re-examine the dopant states of these materials, and also recalculate their electronic structures using the LDA+$U$ method. The improvement achieved with the LDA+$U$ method and comparison with experimental results will be presented. [Preview Abstract] |
Friday, March 19, 2010 12:27PM - 12:39PM |
Z24.00007: Ferroelectric-Ceramic Nanoparticle Composite Materials Synthisized via Physical Vapor Deposition Andrew Pierce This study documents an inquiry into the preparation of ferroelectric polymer-ceramic nanoparticle composite films via physical vapor deposition. The combination of these types of materials has developed an interest in the material science community due to their incredible potential as a dielectric material for capacitor applications. Through the course of this particular investigation, polyvinylidene fluoride (PVDF) containing nanoparticles of titanium dioxide (TiO$_{2}$) were synthesized inside a vacuum. In this study, various parameters of physical vapor deposition were investigated so as to better manipulate the composition of the PVDF/TiO$_{2}$. The resultant composition and distribution of the films were analyzed using x-ray photoelectron spectroscopy (XPS), scanning force microscopy (SFM), and energy dispersive x-ray analysis (EDX). [Preview Abstract] |
Friday, March 19, 2010 12:39PM - 12:51PM |
Z24.00008: Structural and dielectric properties of monodisperse TiO$_{2}$-paraffin core-shell nanoparticles Balasubramanian Balamurugan, Kristin Kraemer, Ralph Skomski, Stephen Ducharme, David Sellmyer Core-shell nanoparticles made of oxides having high dielectric constant and organic materials with large breakdown field are attractive candidates for higher-energy-density capacitors. In the present study, monodispersed TiO$_{2 }$nanoparticles were produced using a cluster-deposition method and subsequently coated with uniform paraffin nanoshells using an \textit{in-situ} thermal evaporation to form core-shell structure. The thickness of the paraffin nanoshells was varied by controlling the evaporation temperature of paraffin. The dielectric properties of TiO$_{2}$-paraffin core-shell nanoparticles show an enhanced effective dielectric constant with a decrease in the thickness of the nanoshells and also, reveal a minimum dielectric dispersion and low dielectric losses in the frequency range of 100 Hz -- 1MHz, which are highly desirable for potential device applications. [Preview Abstract] |
Friday, March 19, 2010 12:51PM - 1:03PM |
Z24.00009: Solid-liquid phase coexistence of alkali nitrates from molecular dynamics simulations Saivenkataraman Jayaraman, Edward Maginn, Anatole Lilienfeld, Aidan Thompson Alkali nitrate eutectic mixtures are finding application as industrial heat transfer fluids in concentrated solar power generation systems. An important property for such applications is the melting point, or phase coexistence temperature. We have computed melting points for lithium, sodium and potassium nitrate from molecular dynamics simulations using a recently developed method [1-3], which uses thermodynamic integration to compute the free energy difference between the solid and liquid phases. The computed melting point for NaNO3 was within 15K of its experimental value, while for LiNO3 and KNO3, the computed melting points were within 100K of the experimental values [4]. We are currently extending the approach to calculate melting temperatures for binary mixtures of lithium and sodium nitrate.\\[4pt] [1] D. M. Eike, J. F. Brennecke, and E. J. Maginn, J. Chem. Phys. 122, 014115 (2005).\\[0pt] [2] D. M. Eike and E. J. Maginn, J. Chem. Phys. 124, 164503 (2006).\\[0pt] [3] S. Jayaraman and E. J. Maginn, J. Chem. Phys. 127, 214504 (2007).\\[0pt] [4] S. Jayaraman, A. P. Thompson, O. A. von Lilienfeld, and E. J. Maginn, I\&EC Res., Accepted (2009). [Preview Abstract] |
Friday, March 19, 2010 1:03PM - 1:15PM |
Z24.00010: Measuring Strain field of Multi-Component Material Systems Using X-Ray Bragg- Surface Diffraction Chia-Hung Chu, Yi-Wei Tsai, Li-Jen Chou, Mau-Tsu Tang, Yuriy P. Stetsko, Shih-Lin Chang We investigated the strain field of the $\beta $-FeSi$_{2}$ semiconductor on a Si(001) substrate, where FeSi in a grain form coexists with $\beta$-FeSi$_{2}$ during the growth of $\beta $-FeSi$_{2}$. The lattice-parameter variations of silicon, $\beta $-FeSi$_{2}$, FeSi and the grain boundary were detected using x-ray Bragg-Surface Diffraction (BSD). With the penetration depth calculated by the dynamical theory of x-ray diffraction, the strain field versus depth of Si-substrate near the interface is determined with the resolution of 0.002 {\AA}. The largest strain detected is about 0.4{\%} up to 8$\sim$12 {\AA} below the interfaces. [Preview Abstract] |
Friday, March 19, 2010 1:15PM - 1:27PM |
Z24.00011: Negative Thermal Expansion and Other Elastic properties of a Class of Solids Yan He, Vladimir Cvetkovic , Chandra Varma We consider the thermal expansion, change of sound velocity with pressure, and the Poisson ratio of lattices which have rigid units (with very large stiffness to change in bond-length and to bond-angle variations) connected to other such units with springs with largestiffness for bond-stretching compared to that required for bond-angle variation at the rigid unit-spring connection. The hierarchy of force constants leads to a negative thermal expansion coefficient over a large range of temperature as well as allows calculation of elastic properties, in particular the Gruneisen constant and the Poisson ratio. We find, consistent with experiments, that crystals with negative thermal expansion coefficients also have sound-velocities which go down with temperature. We also find a very weakly negative Poisson ratio for such solids. [Preview Abstract] |
Friday, March 19, 2010 1:27PM - 1:39PM |
Z24.00012: Bi-Stable Thermal Actuators Julia Aebersold, Brian Goessling, Evgeniya Moiseeva, Cindy Harnett Conventionally, most MEMS devices are constructed and remain within the plane of the wafer. Presented here are devices that have been released from a silicon wafer and generate a profile that can be electrically manipulated above the wafer surface. The advantage of this profile is that the devices can be employed in a gaseous or liquid flow parallel to the wafer surface to capture trace elements or gaseous vapor of interest for either liquid or gas analysis. Additionally, the selection of particular thin films and their thicknesses can benefit from differing thin film stresses to control the shape and profile of the released structures. Electrical manipulation of the devices by varying voltage application can alter the shape of the devices due to thermal heating and differences in the thermal coefficients of expansion of the selected materials. Actuation of the devices can enable possibilities of motion of the device (i.e. walking) or transfer of items from device to device. Presented herein is the fabrication process, the relationship of the shape of the devices based upon the fabricated pattern, thin film metal selection, film thicknesses, with SEM images of the electrically manipulated devices. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700