Bulletin of the American Physical Society
2008 APS March Meeting
Volume 53, Number 2
Monday–Friday, March 10–14, 2008; New Orleans, Louisiana
Session J20: Focus Session: Electronic and Lattice Properties of Surfaces and Thin Films |
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Sponsoring Units: DCMP Chair: Saw-Wai Hla, Ohio University Room: Morial Convention Center 212 |
Tuesday, March 11, 2008 11:15AM - 11:27AM |
J20.00001: Atomic and Electronic structure of Fe$_2$O$_3$ films on MgO(111) K. Pande, A. Celik-Aktas, M. Gajdardziska-Josifovska, M. Weinert Polar oxide surfaces have interesting properties due to the strong ionic character of the metal-oxygen bonds and the layering of metal and oxygen planes parallel to the surface. In this first-principles study we investigate the effect of MgO(111) surface polarity on the structure of iron oxide films. The calculated energetics of different surface terminations on the unreconstructed MgO(111) surface suggest that the interface has a Mg-O-Fe stacking with no intermixing of O and Fe atoms at the interface. The magnetic ordering of Fe atoms both within the layers and between neighboring (bi)layers will be described. The calculated structural and electronic properties will be compared to the results of high-resolution transmission electron microscopy (HRTEM) and selective area diffraction (SAD) experiments of Fe$_2$O$_3$ films on MgO(111) surface. [Preview Abstract] |
Tuesday, March 11, 2008 11:27AM - 11:39AM |
J20.00002: ABSTRACT WITHDRAWN |
Tuesday, March 11, 2008 11:39AM - 11:51AM |
J20.00003: The semiconducting surface of In$_{4}$Se$_{3 }$ M. Klinke, E. Cai, I. Rodriguez, Jiandi Zhang, R. Matzdorf, Y. Losovyi, J. Lui, P.A. Dowben, L. Makinistian, E.A. Albanesi, A. Petukov, Ya. Fiyala, P. Galiy The layered crystal In$_{4}$Se$_{3}$ is of growing interest because of its natural two dimensional structure and anomalies concerning transport properties. We have studied both the lattice and electronic band structures of cleaved (001) surface of In$_{4}$Se$_{3}$. Both LEED and STM reveal a $p$(1$\times $1) surface structure with quasi-one dimensional atomic chains. ARPES data also confirm such quasi-one dimensional character with a very anisotropic band structure. The surface electronic density of states measured by tunneling spectroscopy is compared with theoretical calculations. [Preview Abstract] |
Tuesday, March 11, 2008 11:51AM - 12:03PM |
J20.00004: Theoretical Study of Tip-Induced Band Bending and Local Tunneling Barrier Height on H-Terminated Si(100) Surface Hideomi Totsuka, Satoshi Watanabe In scanning tunneling microscopy (STM) measurements on semiconductor surfaces, tip-induced band bending (TIBB) occurs due to the applied high bias voltage, and influences the local electronic structures of the surface detected by STM and scanning tunneling spectroscopy (STS). Recently, Yoshida et al. have reported the effect of the TIBB on local tunneling barrier height (LBH) on Si(100) surfaces by light-modulated STS [1]. However, theoretical studies on the TIBB and LBH have not been performed yet on semiconductor surfaces. In this study, we have analyzed the TIBB and LBH on an H-terminated Si(100) surface theoretically using the boundary-matching scattering-state density functional method [2], which can calculate the electron states under applied bias voltages self-consistently. In particular, we focus on the bias voltage dependences of the TIBB and LBH, and show that measured LBHs can be basically understood as the sum of TIBB and intrinsic barrier height. [1] S. Yoshida, et al., e-J. Surf. Sci. Nanotech. 4, 192 (2006). [2] Y. Gohda et al., Phys. Rev. Lett. 85, 1750 (2000). [3] M. McEllisterm, et al., Phys. Rev. Lett. 70, 2471 (1993). [Preview Abstract] |
Tuesday, March 11, 2008 12:03PM - 12:15PM |
J20.00005: Studies of the oxidized Cu(100) surface using positron annihilation induced Auger electron spectroscopy W. Maddox, N. G. Fazleev, M. P. Nadesalingam, A. H. Weiss We discuss recent progress in studies of an oxidized Cu(100) single crystal subjected to vacuum annealing over a temperature range from 293K to 1073K using positron annihilation induced Auger electron spectroscopy (PAES). The PAES measurements show a large monotonic increase in the intensity of the positron annihilation induced Cu M2,3 VV Auger peak as the sample is subjected to a series of isochronal anneals in vacuum up to annealing temperature 573 K. The intensity then decreases monotonically as the annealing temperature is increased to 873 K. Experimental PAES results are analyzed by performing calculations of positron surface states and annihilation probabilities of surface-trapped positrons with relevant core electrons taking into account the charge redistribution at the surface, surface reconstructions, and electron-positron correlations effects. The effects of oxygen adsorption and surface reconstruction on localization of positron surface state wave functions and annihilation characteristics are analyzed. Possible explanations are provided for the observed behavior of the intensity of positron annihilation induced Cu M2,3VV Auger peak with changes of the annealing temperature. [Preview Abstract] |
Tuesday, March 11, 2008 12:15PM - 12:27PM |
J20.00006: Visualization of 2D subband states formed in Si(111)-$\beta -\surd $3x$\surd $3-Bi surface by STM Katsumi Nagaoka, Shin Yaginuma, Tadaaki Nagao, Tomonobu Nakayama We have investigated electronic subbands formed underneath of Si(111)-$\beta -\surd $3x$\surd $3-Bi ($\beta -\surd $3-Bi) surface by using STM. The $\beta -\surd $3-Bi surface is semiconducting, and the band gap is larger than that of bulk Si. In the dI/dV images, standing waves are found around defects, and the obtained energy dispersion is in good agreement with the free-electron-like model. Apparently, formation of a 2D electronic state is suggested. However, this standing wave is observed only on p-type, but not on n-type Si substrates, and consequently the 2D state is attributed to the subband formed in the depletion layer just below the $\beta -\surd $3-Bi surface. The subband formation is also consistent with the calculation of electronic states inside a potential-well caused by interfacial band bending. [Preview Abstract] |
Tuesday, March 11, 2008 12:27PM - 12:39PM |
J20.00007: One-Dimensional Electronic Bands of Monatomic Cu Chains Pingheng Zhou, Paolo Moras, Luisia Ferrari, Gustav Bihlmayer, Stefan Bl\"ugel, Carlo Carbone The electronic structure of an array of monatomic Cu chains grown on the Pt(997) surface has been examined by angle-resolved photoemission. The monatomic wires exhibit properties associated to 3d electron confinement in one-dimension. Along the wire direction the 3d bands states display a dispersive character, with periodicity in reciprocal space defined by the wire array geometry. These observations are compared and analyzed with ab initio calculations based the full potential linearized augmented plane wave method. [Preview Abstract] |
Tuesday, March 11, 2008 12:39PM - 12:51PM |
J20.00008: Calculating work functions with density functional theory: the effect of finite temperature, surface alloying, and oxidation Thomas R. Mattsson, Dwight R. Jennison The work functions for W, Cu, and Al are calculated using density functional theory (DFT). We go beyond the perfect lattice at zero Kelvin by employing molecular dynamics techniques. Effects of surface alloying and -oxidation are also investigated. The effect of alloying and oxidation is, as expected, found to be significant, while the temperature dependence, although clearly seen, is in comparison weak. In addition, the exchange-correlation density functional AM05 is compared to the results of LDA and PBE. The calculated work functions compare well to available experimental results. This work was supported by the LDRD office and the simulations were performed at the High Performance Computing facilities at Sandia National Laboratories, NM. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
Tuesday, March 11, 2008 12:51PM - 1:03PM |
J20.00009: Longitudinal Phonon Resonance of the Cu(111) Surface Vasse Chis, Bo Hellsing, Marco Bernasconi, Giorgio Benedek, J. Peter Toennies A density functional perturbation theory investigation of Cu(111) surface dynamics proves that the surface longitudinal acoustic resonance is not an artifact of the inelastic He atom scattering mechanism but a genuine dynamical feature of metal surfaces, and suggests the ability of He atoms to probe the atomic displacements in the second layer through the surface charge modulation they produce. The present results solve the long-standing Bortolani-Mills paradox and reconcile many early apparently divergent interpretations, based on semi-empirical as well as ab-initio methods, of the ubiquitous longitudinal acoustic resonance and clarifies its intrinsic nature. [Preview Abstract] |
Tuesday, March 11, 2008 1:03PM - 1:15PM |
J20.00010: Rashba-type spin-orbit splitting in ultrathin Bi films G. Bihlmayer, Yu. M. Koroteev, E.V. Chulkov, S. Bl\"ugel Due to their electronic similarity with graphene sheets, surfaces and thin films of the semimetal bismuth have recently received considerable interest. A systematic study of thin ($1-6$ bilayers) films in (111) and (110) orientation is presented, employing density functional theory calculations. Due to the different coordination of the surface atoms in these two cases, a large variation of the conducting properties of the films is found. The evolution of surface states is studied as a function of the film thickness and by comparison to thicker films and simulations of the semiinfinite crystals. Interesting features arise from the strong spin-orbit effects in Bi and the resulting Rashba-type spin-splitting of the surface states. The spin-polarization of these states changes as these states transform into quantum well states at the Brillouin zone boundary. The results are compared with recent experimental results on Bi films on Si substrates. [Preview Abstract] |
Tuesday, March 11, 2008 1:15PM - 1:27PM |
J20.00011: Lattice Dynamics of RuO$_{2}$: Bulk and (110) Surface Klaus-Peter Bohnen, Rolf Heid, Omar de la Pena Seaman Although RuO$_2$ has been studied as a prototype catalyst for CO oxidation no careful study of the lattice dynamics for this material has been presented so far. Using modern ab-initio methods we obtain the phonon dispersion and the generalized density of states (GDOS). Inelastic neutron-scattering experiments allow for an experimental determination of the GDOS. In contrast to what is known from structural studies, we find that the local-density approximation gives a much better description of the phonon spectrum than the generalized gradient corrected form. This is also consistent with Raman measurements. Besides the bulk we have also studied the lattice dynamics for the (110) surface. Our calculations indicate an instability over a large range of the BZ. Unfortunately, no complete experimental phonon study of this surface has been carried out so far. Consequences for the structure of the (110) surface will be discussed. [Preview Abstract] |
Tuesday, March 11, 2008 1:27PM - 1:39PM |
J20.00012: Simulation of four-probe measurement based on density-functional tight-binding method Asako Terasawa, Tomofumi Tada, Satoshi Watanabe Four-probe measurements are powerful tools to investigate electric properties of materials precisely. Recently, the minimum probe spacing has reached to the order of 10 nm using nanotube probe tips [1]. However, it is not clear if the procedure used in macroscopic measurements can eliminate the effects of contact resistance even in such microscopic measurements. Keeping this in minds, we have developed a multi- probe transport simulator on the basis of Green's function method combined with the density-functional tight-binding method [2]. So far, we have succeeded in self-consistent calculations at the limit of zero bias voltage for four-probe models consist of more than 1000 atoms, such as an infinite graphite ribbon with two or four semi-infinite nanotube tips. The calculation results indicate that the effects of the contact are not fully eliminated by the usual procedure. \newline [1] S. Yoshimoto, et al., Nano Lett. 7, 956 (2007) \newline [2] T. Frauenheim, et al., Phys. Stat. Sol. 217, 41 (2000) [Preview Abstract] |
Tuesday, March 11, 2008 1:39PM - 1:51PM |
J20.00013: Quantum Blockades and Loop Currents in Graphene with Topological Defects Yan-Yang Zhang, Jiang-Ping Hu, B.A. Bernevig, Xiangrong Wang, Xin-Cheng Xie, Wu-Ming Liu We investigate the effect of topological defects on the transport properties of a narrow ballistic ribbon of graphene with zigzag edges. Our results show that the longitudinal conductance vanishes at several discrete Fermi energies where the system develops loop orbital electric currents with certain chirality. The chirality depends on the direction of the applied bias voltage and the sign of the local curvature created by the topological defects. This novel quantum blockade phenomenon provides a new way to generate a magnetic moment by an external electric field, which can prove useful in carbon electronics. [Preview Abstract] |
Tuesday, March 11, 2008 1:51PM - 2:03PM |
J20.00014: Orbital Order in (LaMnO$_3$)$_m$(SrMnO$_3$)$_n$ Superlattice Chungwei Lin, Claude Ederer, Andrew Millis A realistic model for (LaMnO$_3$)$_m$ (SrMnO$_3$)$_n$ is constructed and solved by the semiclassical approximation. The model includes electron-electron, electron-lattice, and lattice-lattice interactions. Technically, we generalize the semiclassical approximation to the multi-orbital system and include the cooperative Jahn-Teller effect in the impurity problem. Within this framework, we present the orbital order in the superlattice. [Preview Abstract] |
Tuesday, March 11, 2008 2:03PM - 2:15PM |
J20.00015: Direct measurement of core-level relaxation dynamics on a surface- adsorbate system Jing Yin, Luis Miaja-Avila, Guido Saathoff, Chan La-o-vorakiat, Margaret Murnane, Henry Kapteyn, Stefan Mathias, Martin Aeschlimann, Michael Bauer Electronic coupling between an adsorbate and the surface on which it resides is fundamental to the understanding of many surface interactions. However, the interaction of \textit{highly-excited} adsorbate states is an area that has been explored only indirectly to-date. In this work, we present the first direct time-resolved observations of the lifetime of core-excited states of an atom adsorbed onto a surface. By implementing laser-assisted Auger decay on an adsorbate/surface system, we directly measure the lifetime of the 4d$^{-1}$ core level of Xenon on Pt(111) to be 7.1 $\pm$ 1.1 fs. This result opens up time domain measurements of highly-excited state dynamics in materials systems where, because of complex interactions, energy-resolved measurements provide incomplete information. [Preview Abstract] |
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