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Title: Theory of low-energy electron diffraction for detailed structural determination of nanomaterials: Ordered structures

Abstract

To enable the determination of detailed structures of nanomaterials, we extend the theory of low-energy electron diffraction (LEED) to become more efficient for complex and disordered systems. Our new cluster approach speeds up the computation to scale as n log n, rather than the current n{sup 3} or n{sup 2}, with n the number of atoms, for example, making nanostructures accessible. Experimental methods to measure LEED data already exist or have been proposed. Potential application to ordered nanoparticles are illustrated here for C{sub 60} molecules adsorbed on a Cu(111) surface, with and without coadsorbed metal atoms, as well as for adsorbed carbon nanotubes. These demonstrate sensitivity to important structural features such as size and deformation of the nanostructures.

Authors:
; ;  [1];  [1];  [2];  [3];  [4]
  1. Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China)
  2. (China)
  3. Department of Electrical Engineering, University of Washington, Seattle, Washington 98195 (United States)
  4. Department of Electronic Engineering, City University of Hong Kong, Hong Kong (China)
Publication Date:
OSTI Identifier:
20976635
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevB.75.014114; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ATOMS; CALCULATION METHODS; COPPER; DEFORMATION; ELECTRON DIFFRACTION; FULLERENES; LAYERS; MOLECULES; NANOTUBES; PARTICLES; SURFACES

Citation Formats

Gavaza, G. M., Tong, S. Y., Van Hove, M. A., Yu, Z. X., Department of Physics, Zhongshan University, Guangzhou, Tsang, L., and Chan, C. H. Theory of low-energy electron diffraction for detailed structural determination of nanomaterials: Ordered structures. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.014114.
Gavaza, G. M., Tong, S. Y., Van Hove, M. A., Yu, Z. X., Department of Physics, Zhongshan University, Guangzhou, Tsang, L., & Chan, C. H. Theory of low-energy electron diffraction for detailed structural determination of nanomaterials: Ordered structures. United States. doi:10.1103/PHYSREVB.75.014114.
Gavaza, G. M., Tong, S. Y., Van Hove, M. A., Yu, Z. X., Department of Physics, Zhongshan University, Guangzhou, Tsang, L., and Chan, C. H. Mon . "Theory of low-energy electron diffraction for detailed structural determination of nanomaterials: Ordered structures". United States. doi:10.1103/PHYSREVB.75.014114.
@article{osti_20976635,
title = {Theory of low-energy electron diffraction for detailed structural determination of nanomaterials: Ordered structures},
author = {Gavaza, G. M. and Tong, S. Y. and Van Hove, M. A. and Yu, Z. X. and Department of Physics, Zhongshan University, Guangzhou and Tsang, L. and Chan, C. H.},
abstractNote = {To enable the determination of detailed structures of nanomaterials, we extend the theory of low-energy electron diffraction (LEED) to become more efficient for complex and disordered systems. Our new cluster approach speeds up the computation to scale as n log n, rather than the current n{sup 3} or n{sup 2}, with n the number of atoms, for example, making nanostructures accessible. Experimental methods to measure LEED data already exist or have been proposed. Potential application to ordered nanoparticles are illustrated here for C{sub 60} molecules adsorbed on a Cu(111) surface, with and without coadsorbed metal atoms, as well as for adsorbed carbon nanotubes. These demonstrate sensitivity to important structural features such as size and deformation of the nanostructures.},
doi = {10.1103/PHYSREVB.75.014114},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 1,
volume = 75,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • We describe how a recent efficient theory of low-energy electron diffraction (LEED) enables the determination of finite-size and disordered nanostructures. Our cluster approach, called NANOLEED, speeds up the computation to scale as n log n, rather than the usual n{sup 3} or n{sup 2}, with n the number of atoms, for example, thereby making nanostructures accessible. To illustrate this method's capability to determine nanoscale structure, we apply it to calculate LEED intensities for Si nanowires of various lengths and thicknesses as well as for various deviations of these nanowires from the ideal Si bulk structure.
  • Geometric structures of (1[times]1) and (1[times]2) Pt thin films on Pd(110) have been determined by dynamical low-energy electron-diffraction analysis. The (1[times]1) structure is found to exhibit relaxations in the first two interlayer spacings of [Delta][ital d][sub 12]=[minus]11.0% and [Delta][ital d][sub 23]=6.6% at a Pt coverage of one monolayer, and relaxations of [Delta][ital d][sub 12]=[minus]6.6% and [Delta][ital d][sub 23]=4.4% at two monolayers. As for the (1[times]2) structure, the top three layers are found to be Pt. The topmost layer is of the missing-row type, the second layer is slightly row paired (0.06 A), and the third layer is significantly rumpled (0.23more » A). Relaxations in the first four interlayer spacings are found to be [Delta][ital d][sub 12]=[minus]9.5%, [Delta][ital d][sub 23]=[minus]8.0%, [Delta][ital d][sub 34]=[minus]7.3%, and [Delta][ital d][sub 45]=2.2%. Except for a significantly less contracted first interlayer spacing, the (1[times]2) structure of the Pt film mimics the (1[times]2) structure of bulk Pt(110).« less
  • We demonstrate that two-dimensionally resolved diffuse low-energy electron diffraction intensities can be measured with sufficient accuracy and at multiple energies to allow direct inversion for a low coverage (5%) disordered K/Ni(100) surface. The data inversion reveals three-dimensional coordinates of atoms with atom images whose full width at half maximum is less that 1 A in all spatial directions. By varying the angle of incidence, first layer and second layer near-neighbor Ni atoms are separately imaged. This is the first demonstration of multiple-energy internal-source electron holography using measured elastically backscattered electrons.
  • The geometric structure of a NiO(111) film on Ni(100) has been determined by dynamical low-energy electron-diffraction analysis. The oxide film is sufficiently thick and uniform to carry out the analysis in the bulk crystal limit. Four orientational domains of NiO(111) are present. We consider four possible terminations of the oxide film (oxygen or nickel, fcc or hcp sites). Our results indicate that the oxide film terminates with a topmost layer of oxygen in fcc sites, and exhibits a 14.8% contraction in the first interlayer spacing relative to the bulk'' interlayer spacing of the film. The bulk'' lattice parameters of themore » oxide film are found to be uniformly compressed by 2.6% relative to bulk NiO(111). Comparison with other work suggests that oxygen termination, a strong contraction in the first interlayer spacing, and retention of cubic symmetry in deeper layers may be general characteristics of unreconstructed rocksalt(111) surfaces of metal oxide films.« less
  • The surface structure and composition of the (001)- and (111)-oriented surfaces of the ordered Pt{sub 3}Sn alloy were determined by low-energy-electron-diffraction intensity analysis. For both orientations the surface structure corresponds to a bulk truncation model. For the (001) surface, the mixed PtSn'' plane forms the outermost surface layer. Sn atoms in the outermost plane are also significantly upwardly displaced (by about 0.2 A) for both the (001) and the (111) surfaces.