Berlin 2008 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 93: Surface Chemical Reactions

O 93.11: Vortrag

Freitag, 29. Februar 2008, 12:45–13:00, MA 043

STM-induced Switching of Hydrogen on a Silicon(100) Surface: An Open-System Density Matrix Study — •Karl Zenichowski, Tillmann Klamroth, and Peter Saalfrank — Theoretical Chemistry, Institute of Chemistry, University of Potsdam, Germany

STM (scanning tunneling microscope) techniques offer the possibility to reversibly switch a hydrogen atom between two stable conformations on a silicon(100) surface dimer at room temperature [1].

We study the switching dynamics of a hydrogen atom, using an open-system density matrix formalism. The Liouville-von Neumann equation in Lindblad form [2] is solved. Vibrational upward rates are calculated within the framework of first order perturbation theory, including expressions for resonant scattering and dipole coupling with tunneling electrons [3,4]. Vibrational deexcitation is treated by applying harmonic selection rules and scaling laws. Temperature is included via the principle of detailed balance.

The switching process in the high current regime is found to be governed by vibrational ”ladder climbing” and subsequent tunneling in the electronic ground state. The influence of current, bias voltage, isotope mass, electric field, and dissipation strength is examined [5].

[1] U.J.  Quaade et al., Surf. Sci. 415, L1037 (1998). [2] G.  Lindblad, Commun. Math. Phys. 48, 119 (1976). [3] B.N.J.  Persson, J.E.  Demuth, Solid State Commun. 57, 769 (1986). [4] B.N.J.  Persson, A.  Baratoff, Phys. Rev. Lett. 59, 339 (1987). [5] K.  Zenichowski, T.  Klamroth, P.  Saalfrank, in preparation.