Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session C45: Oxide Surfaces and Defects |
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Sponsoring Units: DCMP Chair: Christopher Homes, Brookhaven National Laboratory Room: BCEC 211 |
Monday, March 4, 2019 2:30PM - 2:42PM |
C45.00001: Surface reaction kinetics of dimethyl methylphosphonate (DMMP) on zirconium hydroxide using attenuated total reflection infrared (ATR-FTIR) spectroscopy Seokmin Jeon, Robert B Balow, Grant C Daniels, Jesse S Ko, Pehr E. Pehrsson Amorphous zirconium hydroxide (ZH) attracts growing attention due to its high activity for decomposing toxic chemicals, especially chemical warfare agents (CWA). We synthesize zirconium hydroxide films using cathodic electrodeposition and investigate their surface chemistry to a CWA simulant, dimethyl methylphosphonate (DMMP), using attenuated total reflection infrared spectroscopy (ATR). |
(Author Not Attending)
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C45.00002: Microscopic investigation on surface structures and intrinsic defects of Cu2O(111) Ly Trinh, Taehun Lee, Ganbat Duvjir, Sanghwa Kim, Aloysius Soon, Se Young Jeong, Jungdae Kim Copper (I) oxide or cuprous oxide (Cu2O) is known to be a p-type semiconductor with direct band gap of ~ 2.1 eV. Since most binary oxides exhibit n-type behavior originating from the donor nature of oxygen vacancies, Cu2O has been considered as a p-type counterpart for oxide-based electronics. Although some theoretical studies reported about the origin of p-type nature in Cu2O, atomistic experimental study on this issue has not been conducted yet. In this work, we investigate the surface structures and intrinsic defects of Cu2O(111) via home-built low temperature scanning tunneling microscopy (STM). Thin Cu2O(111) layer is prepared on top of Cu(111) film by ambient oxidation, and the surface of Cu2O(111) is cleaned by Ar sputtering and annealing for STM experiments. STM topography reveals the stoichiometric oxygen-terminated surfaces of Cu2O(111). We also directly observed two types of intrinsic defects which show different contrast in topography depending on bias polarity. These defects are identified by comparison with density functional theory (DFT) simulations. The electronic property of defects will be discussed during the presentation. |
Monday, March 4, 2019 2:54PM - 3:06PM |
C45.00003: Cu2O island growth during Cu oxidation revealed by correlated in situ ETEM and multiscale simulations Meng Li, Matt Curnan, Xinyu Li, Graeme Henkelman, Wissam Saidi, Judith Yang Fundamental understanding of the surface oxidation process is essential for controlling and predicting oxide growth for catalysts and electronic devices applications. Despite numerous studies on the bulk oxidation process, the initial oxide growth process is still less explored, especially at the atomic scale. In this work, by combining in situ Environmental TEM (ETEM) with multiscale atomistic simulation, the dynamic process of initial Cu2O nano island growth was explored. Our ETEM result shows during Cu(100) oxidation, Cu2O nano islands grow through a layer-by-layer adatom growth mechanism along Cu2O(110) surface. Our simulation results show that comparing with Cu2O(100), Cu2O(110) has lower surface energy, lower Cu diffusion energy and more favorable Cu adsorption energy, leading to easier Cu2O monolayer formation along Cu2O(110) that ultimately caused the observed layer-by-layer oxide growth. These results will enhance the understanding of surface oxidation and will also provide insights into understanding initial oxide growth mechanisms of other metal/alloy systems. |
Monday, March 4, 2019 3:06PM - 3:18PM |
C45.00004: First-principles study of Iridium oxide desorption from iridium low-index surfaces at high temperature Insung Seo, Shunsuke Yokota, Yousuke Imai, Yoshihiro Gohda Iridium is one of the noble metals. Although iridium has good chemical inertness and mechanical properties especially at high temperature, iridium has a problem to use, due to the desorption problem[1]. It is known that desorption occurs mainly the form of IrO3 molecule below 1775K[2]. To investigate about iridium desorption problem, theoretical understanding of iridium surface oxide is needed. |
Monday, March 4, 2019 3:18PM - 3:30PM |
C45.00005: Atomic Structure and Nano-Fracture Mechanics of Semiconductor-Oxide Interfaces Investigated by Transmission Electron Microscopy and Scanning Force Microscopy Dipanwita Dutta, Dariusz Jarzabek, Helmut Schift, Zygmunt Rymuza, Thomas Jung Quantitative Information on interface adhesion and fracture resistance is of importance for electronic and MEMS/NEWS device manufacturing. Here we focus on Scanning Force Microscopy derived methods [1] which reveal the mechanical properties and fracture thresholds of oxide with respect to semiconductor interfaces like SiO2/Si and SiO2/SiC. Load/unload cycles i.e. force vs. distance curves reflect the effect of structural defects on interface strength under the influence of fluids solubilising and modifying surface/ interface layers [2]. Nanomechanic properties can be assessed at different time scales. Interface defects are characterized by complementary Microscopic and Spectroscopic Nanoanalysis using STEM and HR-TEM. |
Monday, March 4, 2019 3:30PM - 3:42PM |
C45.00006: Amorphous Networks at the Atomic-Scale: Comparing Two-Dimensional Silica and Germania Kristen Burson, Adrian Lewandowski, Philomena Schlexer, Christin Buechner, Hannah Burrall, Wolf-Dieter Schneider, Gianfranco Pacchioni, Markus Heyde, H J Freund Recently, new insight into the atomic-scale structure of amorphous networks was established through the development of 2D thin-films of known glass formers using scanning tunneling microscopy (STM) in combination with density functional theory (DFT) [1-3]. Here we present a study of two prominent glass-formers, silica and germania, using high-resolution ultra-high vacuum STM to characterize structure. Both SiOx and GeOx films were grown on Ru(0001) by physical vapor deposition and subsequent annealing in oxygen, yielding either crystalline or amorphous structures. STM images reveal a hexagonal network with domain boundary structures in atomically flat monolayer films for both glass formers, with germania showing a greater variety of structures. Bilayer films provide for the development of amorphous structure and similar ring structures are seen for both materials. A few exceptions to the structural analogy are seen experimentally and described by DFT, which predicts a stronger interaction with the metal support for germania. This work reveals commonalities and species dependency for glassy structures. |
Monday, March 4, 2019 3:42PM - 3:54PM |
C45.00007: A non-invasive SOI gating method of probing pristine chemically-terminated silicon surfaces Luke Robertson, Bruce E Kane Silicon has a variety of surface terminations available to it in which surface states are passivated and where 2D electron inversion layers are possible through electrostatic gating. Here, Si(111) surfaces are terminated with hydrogen using a simple wet chemical treatment, and techniques to probe 2D transport on these passivated surfaces have been established. We are presently developing new techniques to probe pristine hydrogen-terminated Si surfaces using a non-invasive SOI flip-chip gating assembly in which all critical device fabrication is performed on the SOI end. Extremely high mobilities, in excess of 300,000 cm2/Vs, have been demonstrated in our previous generation devices, and further refinement of these novel techniques to preserve the pristine nature of these passivated Si surfaces is expected to yield even higher mobilities. Until now, we have focused exclusively on H-Si(111), but are in process of extending our study to include H-Si(100) surfaces. Further, recent progress in halogen-terminated (Cl, Br, I) Si surfaces has provided new avenues for future investigation using our device platform. Architecture details and ohmic contact tests will be presented as well as ongoing low temperature device characterization measurements. |
Monday, March 4, 2019 3:54PM - 4:06PM |
C45.00008: DFT-MD simulations of reaction mechanisms between tricresy phosphate and Fe3O4 (111) surface Naoki Uemura, Shuji Ogata, Yosuke Harada Tricresyl Phosphate (TCP) used, e.g, as an anti-wear additive reacts to form surface layers on metal and metal oxide under high pressure and high temperature. So far, many experimental and theoretical studies have suggested principal factors that affect the reaction: configurational orientations of P=O group of TCP on the surface, water molecules on the surface, and oxygen atoms of oxidized metal. In a recent DFT study [1], three decomposition mechanisms of TCP on pure iron surfaces was investigated. We here perform DFT-MD simulations of gradually pressurized (~10 GPa) TCP on Fe3O4 (111) surfaces to understand the effects of exposed oxygen atoms of the Fe3O4 surfaces and of TCP orientations initially relaxed on the Fe3O4 surfaces. We thereby find that: (i) the P-O bond that connect to the toluene base of TCP breaks in all cases, (ii) the P-O bond breaking is attributed to the attacking by either oxygen or iron atom of the Fe3O4 surfaces, (iii) the adsorption behavior of TCP varies depending on the initial TCP orientations and the amount of exposed oxygen atoms of the Fe3O4 surfaces. |
Monday, March 4, 2019 4:06PM - 4:18PM |
C45.00009: Exceptional scaling relation exhibited by oxygen reduction reaction intermediates on TiO2 surfaces Yoshiyuki Yamamoto, Shusuke Kasamatsu, Osamu Sugino Enhancing the oxygen reduction reaction (ORR) is a major topic of electrocatalysis, and surfaces have long been designed to realize a full alignment of the adsorption energies of the reaction intermediates, O2*, O*, OH* and OOH*. The alignment is not easy to realize because the adsorption energies often change obeying a linear relationship among them, known as the scaling relation, rather than change independently by modifying the surface. Pristine oxide surfaces tend to show the scaling relation [1], but defective TiO2, attracted attention as the electrocatalyst beyond Pt, may behave exceptionally because of the measured high reactivity. |
Monday, March 4, 2019 4:18PM - 4:30PM |
C45.00010: Structural and electronic coupling at the surface of SrTiO3 (001) Mohammad Saghayezhian, S. M. Rezaei, Jiandi Zhang, E Ward Plummer The surface of SrTiO3 (001) is considered to be weakly polar and in this work, we study the validity of this notion. Using low energy electron diffraction at room temperature, a surface structural distortion was found. Structural analysis shows the presence of strong surface rumpling in the TiO2 terminated surface with the Ti and O atoms move in and outward. Density functional calculations confirm the measured rumpling, and experimental data show the distortion is localized at the surface. Angle-dependent core-level X-ray photoemission spectroscopy (XPS) shows that the surface rumpling strongly impacts the electronic structure of the surface. Density functional theory demonstrates that the valence state of Ti at the surface is reduced while O is enhanced. In addition, we found the Ti-O bonds are more covalent near the surface. Changes in the XPS satellite structures at the surface are consistent with this picture of the change in bonding, indicating that the (001) surface of SrTiO3 is not polar and charge rearrangement is a consequence of surface rumpling. We will also present our latest finding on the effect of cubic-tetragonal transition on the surface structure. |
Monday, March 4, 2019 4:30PM - 4:42PM |
C45.00011: Cryogenic force microscopy of Sketched LaAlO3/SrTiO3 Nanostructures Joseph Albro, Jessica H Montone, Feng Bi, Mengchen Huang, Jung-Woo Lee, Hyungwoo Lee, Chang-Beom Eom, Patrick Irvin, Jeremy Levy
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Monday, March 4, 2019 4:42PM - 4:54PM |
C45.00012: Molecular Beam Epitaxy (MBE) Growth of Model Cathode to Study Interfacial Ion Diffusion Bilash KC, Jake R Jokisaari, Robert Klie High performance lithium transition metal oxide battery cathodes, such as LiMn2O4, remain a highly active research area. Single-crystals provide well-defined orientations, defect concentrations, homogeneity, and surface terminations that allow isolation of specific chemical and structural aspects of intercalation to be examined. These features make single crystals highly desirable for characterization of pristine and cycled cathodes, compared to polycrystals/particles. |
Monday, March 4, 2019 4:54PM - 5:06PM |
C45.00013: Homoepitaxial growth of SrTiO3 by Pulsed Laser Deposition: energetic vs thermal growth Jeffrey Ulbrandt, Xiaozhi Zhang, Rui Liu, Matthew Dawber, Randall Headrick The role of energetic processes in homoepitaxial growth of SrTiO3 (STO) by Pulsed Laser Deposition (PLD) was studied via Real-Time X-ray scattering. Two process were developed, an energetic process and a thermal process. Both processes utilized a background gas of 2 mTorr of O2. The thermal process had an additional 300 mTorr of Helium to act as a buffer gas. Langmuir probe measurements verified the energies of the two process to be between 50-100 electron-volts (eV) and 0.02-0.05 eV respectively. Specular X-ray reflectivity, sensitive to inter-layer transport of material, was the same for both processes. Diffuse scattering, sensitive to the in-plane transport of material, was markedly different. In the thermal process, sharp peaks in the diffuse scattering arise with the growth of each successive layer indicating growth of well correlated islands with a well-defined mean spacing. In the energetic process, diffuse scattering peaks also arise at a similar wavevector, though much weaker and broader. These results suggest an energetic process, such as island breakup, may be responsible for the broadening of the diffuse scattering, in which material from the edges of growing islands is broken off into smaller islands. |
Monday, March 4, 2019 5:06PM - 5:18PM |
C45.00014: Surface Stress in nano-oxides and what it tell us Siu-Wai Chan Surface stress of solid surfaces and interfaces is ubiquitous, but has not often been modeled/calculated. In this short talk, experimental results definitely prove that surface stress exists in nanocrystals and can be modified with adsorbents affecting the material’s basic properties such as stiffness and thermal expansion. It is particularly influential in surface/interface dominated systems such as thin films and nanoparticles. Whether we choose to deal with it, it will often spring surprises on us during processing for advanced architecture in novel device integration. |
Monday, March 4, 2019 5:18PM - 5:30PM |
C45.00015: Adsorption and destruction of nerve agent sarin and its simulant DMMP on zinc oxide Roman Tsyshevskiy, Scott Holdren, Kenan Fears, Jeffrey Owrutsky, Bryan Eichhorn, Michael Zachariah, Maija M Kukla Discovery and design of new filter materials requires an atomistic level understanding of how these materials interact with toxic agents. High toxicity of chemical warfare agents (CWAs) is the main barrier for experimental study of these compounds which hinders the search for improved filter materials. To fill the gaps in the understanding of CWA interactions with existing and potential filter materials, relatively benign simulant compounds are usually used to replace toxic CWAs. Despite structural similarity of the simulants with real chemical agents the questions have been frequently raised about the reliability of the results obtained for CWA simulants and ability to extrapolate these results to real toxins. Here we report results of our joint DRIFTS, FTIR and DFT study of adsorption and destruction of dimethyl methylphosphonate (DMMP) simulant molecule on ZnO nanoparticles. The synergy between theory and experiment enables further DFT modeling of interactions of the nerve agent sarin with pristine and hydroxylated ZnO surfaces. Results of this work provide new important details on mechanisms and kinetics of destruction of these compounds on ZnO. |
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