The interplay of adsorption geometry and interface dipoles of the transition-metal complex Ir(ppy)3 on Cu(111) was studied using low-temperature scanning probe microscopy and density-functional-theory calculations. We find that the orientation of the molecule's intrinsic dipole moment with respect to the surface has a strong influence on the total energy of the different configurations, where the most stable one has the molecular dipole moment pointing out of the surface plane along the surface normal. Adsorption-induced redistribution of charges results in an additional dipole moment that also points out of the surface plane for all configurations. Submolecularly resolved maps of the resulting local contact potential difference suggest that any in-plane dipole moment is very effectively screened.

Department of Physics Engineering Physics and Astronomy Queen's University Kingston ON CanadaK7L3N6

Department of Physics University of Regensburg 93053 Regensburg Germany

Institute of Physics Academy of Sciences of the Czech Republic Cukrovarnická 10 CZ 162000 Prague Czech Republic

Institute of Physics Academy of Sciences of the Czech Republic Cukrovarnická 10 CZ 162000 Prague Czech Republic and Department of Applied Physics Aalto University P O Box 11000 FI 00076 Aalto Finland

Institute of Physics Academy of Sciences of the Czech Republic Cukrovarnická 10 CZ 162000 Prague Czech Republic and Regional Centre of Advanced Technologies and Materials Palacký University ŝlechtitelů 27 78371 Olomouc Czech Republic

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