Resumenes de las Charlas Invitadas
Theoretical study of the dimer dynamics on the Si(001) surface: role of surface defects
Chu-Chun Fu+,*,
Mariana Weissman+,
and Andrés Saúl*
+Departamento de Física, Comisión Nacional de Energía Atómica,
Avda. del Libertador 8250, 1429 Buenos Aires, Argentina.
*Centre de Recherche sur les Mécanismes de la Croissance Cristalline,
CNRS, Campus de Luminy, Case 913, 13288 Marseille Cedex 9, FRANCE.
Abstract
The Si(001) surface reconstructs forming buckled dimer rows in order to reduce the surface energy.
These dimer rows are stable up to 1463K, close to the temperature at which the surface becomes
rough. Therefore the surface dimers are considered as building units on Si(001). In a clean area of
the surface, far from defects, the principal movement of surface dimers consists of a flipping or
vibration between two equivalent buckling angles. The dimers that are close to a surface defect
usually present three possible local minima, two of them buckled, with positive and negative
buckling angles, and the third, symmetric.
According to previous high temperature molecular dynamics studies surface dimers participate
strongly in ad-atom and ad-dimer diffusion on Si(001), through concerted motions and atom
exchanges. Therefore the dimer dynamics and its modification at different local environments could
strongly affect the surface diffusion, and consequently the epitaxial growth. Motivated by the
above mentioned importance of surface dynamics, and also by recent experimental STM results which
show large differences in the flipping energy barriers (of about 0.1 eV) depending on the local
environment, we have performed a detailed study of the dimer dynamics at finite temperature near
surface defects.
We have found Some similarities in the dynamics between dimers close to single dimer vacancies
(SDV), steps, and steps with kinks. First neighbors of a SDV, upper step B edge dimers, and dimers
close to kinks in step A have similar local environment. Therefore all tend to flip faster, and
spend most of the time symmetric. On the other hand, second neighbors of a SDV, upper step A edge
dimers, and dimers close to kinks in step B tend to flip slower.
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