Chang, CY, Lin ZC, Chou YC, Wei CM.
1999.
Direct three-dimensional Patterson inversion of low-energy electron diffraction I(E) curves, Sep. Physical Review Letters. 83:2580-2583., Number 13
AbstractA Patterson-like scheme is proposed for direct inversion of the conventional low-energy electron diffraction (LEED) intensity versus energy I(E) curves, which is in contrast with the previously suggested holographic scheme. Using the Si(111)-(7 X 7) and Si(113)-(3 X 2) surfaces as examples, high quality three-dimensional images, with a resolution better than 0.5 Angstrom, of both surface atoms and bulk atoms are obtained from the direct Patterson inversion of LEED-I(E) curves with the integral-energy phase-summing method.
Chang, CS, Su WB, Wei CM, Tsong TT.
1999.
Large Fermi density waves on the reconstructed Pt(100) surface, Sep. Physical Review Letters. 83:2604-2607., Number 13
AbstractSeveral long-range superstructures have been observed with the scanning tunneling microscopy on the reconstructed Pt(100) surface at room temperature. They are present in strained domains and involve both the Fermi electrons and the concomitant lattice distortions. A first-principles calculation shows that the top layer expanded similar to 18% on average and the Fermi surface for a single hexagon layer displays some nesting portions, which can be related to the wave vectors of the observed superstructures. Thus, these superstructures existing in the local domains of the reconstructed surface have the likely origin of incipent charge density waves.
Chang, CM, Wei CM.
1999.
Structure and dynamics of Al trimer on Al(111) surface, Oct. Surface Review and Letters. 6:787-792., Number 5
Abstract{
Trimer is the smallest cluster that can have a one-dimensional or a two-dimensional structure on fee (111) surface. Using first-principles density-functional-theory calculations, the structural and dynamical properties of Al trimer on Al(111) surface have been studied in detail. Al trimer on Al(111) surface has four close-packed (compact) triangular configurations, two linear configurations, and some other noncompact triangular configurations. The close-packed triangular trimers are more stable than the noncompact triangular trimers as well as the linear trimers. For the dynamics of Al trimer on Al(111) surface, the diffusion processes are much more complicated than the adatom and dimer diffusions. There are three different kinds of diffusion mechanisms: concerted translations and rotation of compact triangular trimers (the energy barrier
Abukawa, T, Wei CM, Hanano T, Kono S.
1999.
Correlated thermal diffuse scattering in low to medium energy electron diffraction: A new structural tool, Jan. Physical Review Letters. 82:335-338., Number 2
AbstractWe have observed simple oscillations in three-dimensional (3D) patterns of electron thermal diffuse scattering (separated from electron-electron energy loss) measured on a Si(001) surface. We interpret these oscillations as coherent interference within a small cluster of atoms in which vibrational correlation within the nearest neighbors (NN) is dominant. A 3D Patterson function analysis of the oscillation reveals the atomic structure of the Si(001) surface consisting of NN pairs including dimers. This finding provides a promising new clue to determine the structures of bulk and the surface of solids.
Shen, TS, Chang CY, Chou YC, Wei CM.
1999.
Holographic images of adatoms, dimers and rest atoms on the Si(111)-(7x7) surface, Feb. Surface Review and Letters. 6:97-101., Number 1
AbstractThe adatoms, dimers and rest atoms in the three outermost atomic layers of the Si(111)-(7 x 7) surface are directly imaged with glancing Kikuchi electron holography. The applicability of Kikuchi electron holography to complicated multiple-emitter surfaces is evident. The three-dimensional relative positions of atoms on the Si(111)-(7 x 7) surface are in good accordance with the LEED-optimized DAS model.
Chang, CY, Shen TS, Chou YC, Wei CM.
1999.
Direct observations of the surface atomic structure of the Si(111)-(7x7) reconstructed surface with Kikuchi electron holography, Dec. Surface Review and Letters. 6:967-976., Number 6
AbstractMore than 50 symmetry-inequivalent emitter-scatterer (E-S) pairs were observed for the Si(111)-(7 x 7) surface using Kikchi electron holography (KEH) with various incident/detection configurations. For different configurations, the E-S pairs in the backscattering direction are preferentially enhanced. Thus, one can obtain detailed structural information by changing the incident/detection direction, which will be helpful in sorting out the correct surface structure model.
Chang, CY, Chou YC, Wei CM.
1999.
Atomic structures and phase transitions of Si(113) reconstructed surfaces: Kikuchi electron holography studies, Apr. Physical Review B. 59:10453-10456., Number 16
AbstractAtomic structures of the reconstructed Si(113) surfaces were studied by using Kikuchi electron holography (KEH). Three-dimensional images show clearly the characteristics of the puckering model for both Si(113)(3x2) and (3x1) surfaces. The KEH results support the puckering model. Based on bur studies, the tetramers are puckering alternatively in the (3x2) surface. Whereas in (3X1) structures, there are two domains, within each of them, tetramers buckled uniformly, but the overall directions are opposite. When doped with H atoms on a (3x2) surface, the asymmetric tetramers change into symmetric form. [S0163-1829(99)51116-8].
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