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A FIRST-PRINCIPLES STUDY OF LI-METAL ADSORPTION ON A SI(100) SURFACE
No full textWe present the results of self-consistent ab initio pseudopotential calculations for the equilibrium structure of Li adsorbed Si(100) surfaces. The stable adsorption sites ale determined for a wide range of Li coverage (Theta=1/2-2). At half-monolayer coverage, the 2x2 structure with Li atoms occupied at the interdimer bridge sites is found to be most stable, while at one-monolayer coverage Li atoms are adsorbed at both the pedestal and cave sites, exhibiting a 2x1 structure where the Si dimers are symmetric. At Theta=2, we find the most stable phase to be the 1x1 structure, which is formed by breaking all the Si dimers of the substrate. From the calculated formation energies, we suggest that the saturation coverage is Theta=2
Ge adatom adsorption, diffusion, and exchange on surfactant-covered Si(111) surfaces
No full textWe investigate the effects of various surfactants on the Ge adsorption, diffusion, and exchange on Si(111) surfaces through first-principles pseudopotential total-energy calculations. For surfactant-covered surfaces such as Si(111):Ga-1 x 1, Si(111):As-1 x 1,and Si(111):Sb-(root 3 x root 3)R30 degrees, Ge adatoms are generally incorporated into the surfactant layer. On the Ga-covered surface, we find-strong interactions between the Ge and Ga atoms, which result in large activation energies for both Ge surface diffusion and exchange with an underlying Ga atom. In the case of As surfactants, the activation energies for adatom diffusion and exchange are much reduced because of the weak couplings between the Ge and As atoms. Similarly, on the Sb-covered surface, the exchange between the adatoms and surfactants takes place easily; however, the surface diffusion is severely suppressed due to a relatively large energy gain by the exchange process. [S0163-1829(99)00128-9]
An ab initio Study of Ge Adatom Diffusion and Exchange on Surfactant-terminated Si(111) Surfaces
No full text
An ab initio Study of the Atomic and Electronic Structure of Li Adsorbed Si(100) Surfaces
No full textAb initio Study of Ge Adatom Adsorption Diffusion and Exchange on Surfactant-covered Si(111) Surfaces
No full textAtomic and electronic structure of Li-adsorbed Si(100) surfaces
No full textWe investigate the atomic and electronic structure of Li-adsorbed Si(100) surfaces through first-principles pseudopotential calculations. We find that Li adatoms interact mainly with the dangling-bond orbitals of Si dimers, however, no hydrogenlike directional bonds exist between the Li and substrate Si atoms, based on calculated scanning tunneling microscopy images. The analysis of charge densities demonstrates a large charge transfer from the Li adatom to a dangling-bond orbital of a Si dimer, which is responsible for a large decrease of work function at submonolayer coverages. The Li atoms form linear chains either by occupying the interdimer bridge sites along the dimer row direction or the dimer bridge and cave sites perpendicular to the dimer row. As Li coverage (Theta) increases, repulsive interactions between the adatoms in the chains are also found to increase. Thus, at 1-ML Li coverage, the stable adsorptions sites are changed to either the cave and pedestal sites or the valley-bridge and pedestal sites, with all the Si dimers symmetric, resulting in a 2x1 structure. From the calculated formation energies, we find a 1x1 phase to be thermodynamically stable at Theta=2, in contrast to other alkali-metal adsorptions.
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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