Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 73: Surface dynamics: Reactions, elementary processes and phase transitions II
O 73.2: Vortrag
Mittwoch, 14. März 2018, 17:00–17:15, MA 043
Semiconductor surface chemistry induced by electronic excitation – tip-induced ether cleavage on Si(001) — Gerson Mette1, Alexa Adamkiewicz1, Tamam Bohamud1, Marcel Reutzel1, •Michael Dürr2, and Ulrich Höfer1 — 1Philipps-Universität, 35037 Marburg — 2Justus-Liebig-Universität Giessen, 35392 Giessen
Reactions of organic molecules on silicon typically proceed via an intermediate state and the conversion barrier between intermediate and final state determines the final products. Electronic excitation, e.g., by tunneling electrons from an STM tip, can open additional reaction channels which are not accessible by means of thermal activation.
Here we show that tip-induced cleavage of the datively bonded intermediate of THF on Si(001)[1] leads to covalently bound final configurations which are not observed for the thermally activated reaction. We find one single threshold in the dependence of the conversion rate on applied bias for all final configurations. Below the threshold, the conversion rate depends nonlinearly on the tunneling current, indicating a reaction induced via multiple excitations of vibrational modes. Above the threshold, this dependence is linear, indicating direct excitation by electron transfer into the antibonding C-O orbital of THF. In the latter case, the molecules on the excited PES are not subject to the strong restrictions which control the transition state on the ground state PES, thus leading to the observed larger variety of final products.
[1] G. Mette, et al., ChemPhysChem 15, 3725 (2014).