title: Impact of Electrode Density of States on Transport through Pyridine-Linked Single Molecule Junctions.
abstract: We study the impact of electrode band structure on transport through single-molecule junctions by measuring the conductance of pyridine-based molecules using Ag and Au electrodes. Our experiments are carried out using the scanning tunneling microscope based break-junction technique and are supported by density functional theory based calculations. We find from both experiments and calculations that the coupling of the dominant transport orbital to the metal is stronger for Au-based junctions when compared with Ag-based junctions. We attribute this difference to relativistic effects, which result in an enhanced density of d-states at the Fermi energy for Au compared with Ag. We further show that the alignment of the conducting orbital relative to the Fermi level does not follow the work function difference between two metals and is different for conjugated and saturated systems. We thus demonstrate that the details of the molecular level alignment and electronic coupling in metal-organic interfaces do not follow simple rules but are rather the consequence of subtle local interactions.
authors.affiliation: †Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States.
authors.forename: Olgun
authors.initials: O
authors.lastname: Adak
authors.affiliation: ‡Institute of Nanotechnology, Karlsruhe Institute of Technology, 76344 Karlsruhe, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Korytár
authors.affiliation: †Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States.
authors.forename: Andrew Y
authors.initials: AY
authors.lastname: Joe
authors.affiliation: §Institute of Theoretical Physics, University of Regensburg, D-93040 Regensburg, Germany.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Evers
authors.affiliation: †Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States.
authors.forename: Latha
authors.initials: L
authors.lastname: Venkataraman
keywords: Single-molecule junctions; density functional theory; density of states; electronic coupling; level alignment; second harmonic generation