Article ID Journal Published Year Pages File Type
5424299 Surface Science 2009 7 Pages PDF
Abstract

Density functional theory calculations have been performed to determine the adsorption site of carbon at the Si(1 1 1):As and Si(1 1 1):H surfaces at different coverages. The As- and H-passivated surfaces were simulated by replacing the topmost Si layer by As or by saturating the Si dangling bonds with hydrogen atoms, respectively. Different high symmetry sites were considered. Carbon was placed successively in the fourfold (T4) or threefold coordinated (H3), the ontop (T1) sites or substituted for a Si atom in the S5 position located underneath the Si adatom in the T4 site. We found that the preferred carbon adsorption site depends on the coverage of the passivated surfaces. At low coverages i.e. at 1/16 ML and 1/3 ML, it prefers a distorted T4 position whereas at 1 ML, it occupies an H3 site. This contrasts with the clean surface where the most energetically favored site is the S5 at all coverages. Carbon adsorption induces a significant change in the structural geometry of the surface atoms, leading to a charge re-arrangement in the surface layers.

Related Topics
Physical Sciences and Engineering Chemistry Physical and Theoretical Chemistry
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