Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 17: Metal substrates: Adsorption of organic / bio molecules III

O 17.6: Talk

Monday, March 14, 2011, 18:30–18:45, TRE Phy

Modification of the electronic properties of Au/molecule/Pd junctions by adsorbed hydrogen: a DFT study — •Jan Kučera and Axel Groß — Institut für Theoretische Chemie, Universität Ulm, D-89069 Ulm, Germany

Metal-molecule-metal contacts assembled from a Pd monolayer deposited on a Au-supported self-assembled monolayer (SAM) of 4-mercaptopyridine or 4-aminothiophenol were recently achieved by means of an electrochemical approach [1]. Subsequent photoelectron spectroscopy showed a strongly reduced Pd density of states (DOS) at the Fermi energy [2]. This phenomenon is still not fully comprehended, however, its understanding is crucial for the use of the sandwich design as a platform for future nanoelectronics.

Periodic density functional theory (DFT) calculation revealed that the dehydrogenation of the amino group and the subsequent strong bonding of the remaining nitrogen atom to the Pd layer could explain the observed modification of the DOS [3]. We have now extended this study in order to clarify the role of hydrogen atoms for the electronic properties of the Pd layers. In equilibrium, these layers should always show a considerable hydrogen coverage in an aqueous environment. Our calculations demonstrate that indeed the adsorbed hydrogen atoms significantly modify the electronic structure of the Pd layers.

[1] F. Eberle et. al., Angew. Chem. Int. Ed. 49, 341-345 (2010)

[2] H.-G. Boyen et. al., Nature Materials 5, 394 (2006)

[3] J. Kučera and A. Groß, Phys. Chem. Chem. Phys. 12, 4423 (2010)