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O: Fachverband Oberflächenphysik
O 102: Heterogeneous Catalysis on Metals
O 102.5: Vortrag
Donnerstag, 19. März 2020, 11:45–12:00, TRE Phy
Chemical bond formation showing a transition from physisorption to chemisorption — Ferdinand Huber1, •Julian Berwanger1, Svitlana Polesya2, Sergiy Mankovsky2, Hubert Ebert2, and Franz J. Giessibl1 — 1University of Regensburg, 93040 Regensburg, Germany — 2LMU Munich, 81377 Munich, Germany
Surface molecules can transition from physisorption through weak van der Waals forces to a strongly bound chemisorption state by overcoming an energy barrier [1,2]. We show that a carbon monoxide (CO) molecule adsorbed to the tip of an atomic force microscope (AFM) [3] enables a controlled observation of bond formation, including its potential transition from physisorption to chemisorption. During imaging of copper (Cu) and iron (Fe) adatoms on a Cu(111) surface, the CO was not chemically inert but transited through a physisorbed local energy minimum into a chemisorbed global minimum, and an energy barrier was seen for the Fe adatom. Density functional theory reveals that the transition occurs through a hybridization of the electronic states of the CO molecule mainly with s-, pz-, and dz2-type states of the Fe and Cu adatoms, leading to chemical bonding. The absence of hybridization 200 pm off-center the individual Fe and Cu adatoms results in the appearance as repulsive tori [4] in the AFM’s image [5].
[1] A. Zangwill, Physics at Surfaces, Cambridge Univ. Press (1988)
[2] H. Ibach, Physics at Surfaces and Interfaces, Springer (2006)
[3] L. Gross et al. Science 325, 1110 (2009)
[4] M. Emmrich et al. Science 348, 6232 (2015)
[5] F. Huber et al. Science 366, 235 (2019)