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J Phys Condens Matter ; 28(43): 435001, 2016 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-27603175


The atomic geometry, stability and electronic properties of self-organized Au induced nanowires on a Ge(0 0 1) surface are investigated based on the density-functional theory in the generalized gradient approximation and the stoichiometry of Au. According to the formation energy and the simulated STM image, the Ge atoms substituted by the Au atoms have been confirmed as occurring at a Au coverage lower than 0.25 Ml. The STM image with single and double dimer vacancies looks like the Au atoms have penetrated the subsurface. The energetically favorable dimer-row arrayed structures at 0.50 Ml and 0.75 Ml Au coverages have a 4 × 1, 4 × 2 or c(8 × 2) transition symmetry, which comprise a flat Au-Au homodimer row and an alternating various buckling phase Ge-Ge or Au-Ge dimer row. The c(8 × 2) zigzag-shaped protruding chains of shallow-groove STM images are highly consistent with the observations, but a long-range order dimer-row arrayed structure formation requires sufficient mobile energy to complete mass transport of the substituted Ge atoms in order to avoid the re-adsorption of these atoms; otherwise a deep-groove structure reconstruction is sequentially formed. A quasi-1D electron-like energy trough aligns in the direction perpendicular to the nanowire of the dimer-row arrayed structure in the c(8 × 2) phase on a 0.75 Ml Au/Ge(0 0 1) surface, which is contributed by the Au-Ge dimer rows and the subsurface Ge atoms below them. The bottom energy of the energy trough is consistent with angle-resolved photo-emission spectroscopy studies (Schäfer et al 2008 Phys. Rev. Lett. 101 236802, Meyer et al 2011 Phys. Rev. B 83 121411(R)).

J Chem Phys ; 132(3): 034502, 2010 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-20095743


In terms of an interatomic pair potential, which well characterizes the dynamic properties of liquid Ga, we investigate again the origin of the well known high-q shoulder in the static structure factor of the liquid. Similar to the results of Gong's simulation at high temperature, dimers with extremely short bond lengths are indeed found in our model just above the melting point, but our results indicate that it is unlikely for the high-q shoulder to be produced by these dimers. Instead, based on our model, the high-q shoulder is resulted from some medium-range order, which is related to the structures beyond the first shell of the radial distribution function, caused by Friedel oscillations within a nanoscale range.

J Chem Phys ; 127(3): 034708, 2007 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-17655456


The Cl abstraction by gas-phase H atoms from a Cl-terminated Si(100) surface was investigated by scanning tunneling microscopy (STM), high-resolution core level photoemission spectroscopy, and computer simulation. The core level measurements indicate that some additional reactions occur besides the removal of Cl. The STM images show that the Cl-extracted sites disperse randomly in the initial phase of the reaction, but form small clusters as more Cl is removed, indicating a correlation between Cl-extracted sites. These results suggest that the hot-atom process may occur during the atom-adatom collision.