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Abukawa, T., Wei C. M., Yoshimura K., & Kono S. (2000).  Direct method of surface structure determination by Patterson analysis of correlated thermal diffuse scattering for Si(001)2X1. Physical Review B. 62, 16069-16073., Dec, Number 23 AbstractWebsite

A simple oscillatory intensity variation in medium-energy electron diffraction found recently [Abukawa ei al., Phys. Rev. Lett. 82, 335 (1999)] was termed correlated thermal diffuse scattering (CTDS). The potential of CTDS as a direct surface structural tool has been fully explored for the Si(001)2 X 1 surface at 300 K in a very-grazing-incidence condition. Nearly 2 pi solid-angle, three-dimensional (3D) CTDS patterns were measured for an energy range of 500-2000 eV. The 3D Patterson functions obtained by Fourier inversion of the measured CTDS patterns clearly revealed the building blocks of the Si(001)2 X 1 surface, i.e., the bond orientations and lengths of the buckled Si dimers, within an accuracy of 1 degrees and 0.1 Angstrom, respectively.

Abukawa, T., Wei C. M., Hanano T., & Kono S. (1999).  Correlated thermal diffuse scattering in low to medium energy electron diffraction: A new structural tool. Physical Review Letters. 82, 335-338., Jan, Number 2 AbstractWebsite

We 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.

Ahn, H., Wu C. L., Gwo S., Wei C. M., & Chou Y. C. (2001).  Structure determination of the Si3N4/Si(111)-(8 x 8) surface: A combined study of Kikuchi electron holography, scanning tunneling microscopy, and ab initio calculations. Physical Review Letters. 86, 2818-2821., Mar, Number 13 AbstractWebsite

A comprehensive atomic model for the reconstructed surface of Si3N4 thin layer grown on Si(lll) is presented. Kikuchi electron holography images clearly show the existence of adatoms on the Si3N4(0001)/Si(111)-(8 x 8) surface. Compared with the nb initio calculations, more than 30 symmetry-inequivalent atomic pairs in the outmost layers are successfully identified. Scanning tunneling microscopy (STM) images show diamond-shaped unit cells and nine adatoms in each cell. High-resolution STM images reveal extra features and are in good agreement with the partial charge density distribution obtained from total-energy calculations.