Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 13: Semiconductor substrates: Adsorption
O 13.10: Vortrag
Montag, 22. März 2010, 17:15–17:30, H34
First-principles study of H diffusion on Si(001) — •Jürgen Wieferink1,2, Peter Krüger1, and Johannes Pollmann1 — 1Institut für Festkörpertheorie, Universität Münster — 2Fritz-Haber-Institut, Berlin
Hydrogen diffusion on the Si(001)-(2×1) surface is crucial for an understanding of molecular H2 desorption. On flat Si(001) terraces, only diffusion along the dimer rows is found for moderate temperatures and low H coverage. On the other hand, the occurrence of vacancy interrow transitions on a monohydride surface has been demonstrated by a recent study combining pulsed laser heating and scanning tunneling microscopy (STM) [1].
After a general introduction of the experimental findings we will present the results of our ab initio study on activation energies and diffusion rates as function of H coverage. The barrier energies depend strongly on the distance between the Si atoms in the transition state. As the monohydride surface is more rigid than the clean surface, isolated vacancies are less mobile than isolated H atoms. Interestingly, two adjacent vacancies may transfer charge from one to another prior to a vacancy transition, which significantly lowers the barrier.
[1] C. H. Schwalb, M. Dürr, U. Höfer, Phys. Rev. B 80,
085317 (2009).