Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 63: Semiconductor substrates: Adsorption
O 63.5: Vortrag
Freitag, 27. März 2009, 12:15–12:30, SCH A118
Site-selective reactivity of ethylene on hydrogen pre-covered Si(001) — •Gerson Mette1, Michael Dürr1,2, and Ulrich Höfer1 — 1Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, D-35032 Marburg — 2Fakultät Angewandte Naturwissenschaften, Hochschule Esslingen, D-73728 Esslingen
The reactivity of a semiconductor surface is expected to correlate not only with the concentration of dangling bonds but also with the local electronic properties of the dangling-bond states. For H2 dissociation on Si(001), a strongly activated process, site-selective reactivity at locally distorted configurations was demonstrated, e.g. by pre-adsorption of atomic hydrogen [1]. In this study, site-selective adsorption of ethylene on Si(001) has been investigated by means of STM. Two ethylene adsorption geometries were found on clean Si(001) with ethylene adsorbed on one and two dimers, respectively. Distortion of the electronic configuration by pre-adsorption of atomic hydrogen is found to increase the reactivity of the two-dimer adsorption site by a factor of 50. Thus, locally distorted dangling-bond configurations show site-selective reactivity also in the case of barrierless, non-dissociative adsorption of an organic molecule. The results are discussed with respect to a precursor mediated adsorption pathway and the control of the adsorption barrier between precursor and chemisorbed state.
[1] M. Dürr and U. Höfer, Surf. Sci. Rep. 61, 465 (2006)