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The molecule-metal bond of alternant versus nonalternant aromatic systems on coinage metal surfaces: naphthalene versus azulene on Ag(111) and Cu(111)

DOI: 10.1021/acs.jpcc.9b08824 DOI Help

Authors: Benedikt P. Klein (Philipps-Universität Marburg) , Juliana M. Morbec (Universität Duisburg-Essen) , Markus Franke (Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich; Jülich Aachen Research Alliance (JARA) – Fundamentals of Future Information Technology) , Katharina K. Greulich (Philipps-Universität Marburg) , Malte Sachs (Philipps-Universität Marburg) , Shayan Parhizkar (Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich; Jülich Aachen Research Alliance (JARA) – Fundamentals of Future Information Technology) , Francois C. Bocquet (Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich; Jülich Aachen Research Alliance (JARA) – Fundamentals of Future Information Technology) , Martin Schmid (Philipps-Universität Marburg) , Samuel J. Hall (University of Warwick) , Reinhard J. Maurer (University of Warwick) , Bernd Meyer (Friedrich-Alexander-Universität Erlangen-Nürnberg) , Ralf Tonner (Philipps-Universität Marburg) , Christian Kumpf (Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich; Jülich Aachen Research Alliance (JARA) – Fundamentals of Future Information Technology) , Peter Kratzer (Universität Duisburg-Essen) , J. Michael Gottfried (Philipps-Universität Marburg)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: The Journal Of Physical Chemistry C

State: Published (Approved)
Published: November 2019
Diamond Proposal Number(s): 16259

Abstract: Interfaces between polycyclic π-electron systems and metals play prominent roles in organic or graphene-based (opto)electronic devices, in which performance-related parameters depend critically on the properties of metal/semiconductor contacts. Here, we explore how the topology of the π-electron system influences the bonding and the electronic properties of the interface. We use azulene as a model for nonalternant pentagon-heptagon (5-7) ring pairs and compare it to its isomer naphthalene, which represents the alternant 6-6 ring pair. Their coverage-dependent interaction with Ag(111) and Cu(111) surfaces was studied with the normal-incidence X-ray standing wave (NIXSW) technique, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, UV and X-ray photoelectron spectroscopy (UPS, XPS), and density functional theory (DFT). Coverage-dependent adsorption heights and spectroscopic data reveal that azulene forms shorter interfacial bonds than naphthalene and engages in stronger electronic interactions with both surfaces. These differences are more pronounced on Cu. Increasing coverages lead to larger adsorption heights, indicating bond weakening by intermolecular repulsion. The extensive DFT calculations include dispersive interactions using: (1) the DFT-D3 scheme, (2) the vdWsurf correction based on DFT-TS, (3) a Many-Body Dispersion (MBD) correction scheme, and (4) the D3surf scheme. All methods predict the adsorption heights reasonably well with an average error below 0.1 Å. The stronger bond of azulene is attributed to its nonalternant topology, which results in a reduced HOMO-LUMO gap and brings the LUMO energetically close to the Fermi energy of the metal, causing stronger hybridization with electronic states of the metal surfaces.

Subject Areas: Chemistry, Materials


Instruments: I09-Surface and Interface Structural Analysis