Understanding the adsorption of CuPc and ZnPc on noble metal surfaces by combining quantum-mechanical modelling and photoelectron spectroscopy

Yu Li Huang, Elisabeth Wruss, David A. Egger, Satoshi Kera, Nobuo Ueno, Wissam A. Saidi, Tomas Bucko, Andrew T.S. Wee, Egbert Zojer

Research output: Contribution to journalArticlepeer-review

70 Scopus citations

Abstract

Phthalocyanines are an important class of organic semiconductors and, thus, their interfaces with metals are both of fundamental and practical relevance. In the present contribution we provide a combined theoretical and experimental study, in which we show that state-of-the-art quantum-mechanical simulations are nowadays capable of treating most properties of such interfaces in a quantitatively reliable manner. This is shown for Cu-phthalocyanine (CuPc) and Zn-phthalocyanine (ZnPc) on Au(111) and Ag(111) surfaces. Using a recently developed approach for efficiently treating van der Waals (vdW) interactions at metal/organic interfaces, we calculate adsorption geometries in excellent agreement with experiments. With these geometries available, we are then able to accurately describe the interfacial electronic structure arising from molecular adsorption. We find that bonding is dominated by vdW forces for all studied interfaces. Concomitantly, charge rearrangements on Au(111) are exclusively due to Pauli pushback. On Ag(111), we additionally observe charge transfer from the metal to one of the spin-channels associated with the lowest unoccupied p-states of the molecules. Comparing the interfacial density of states with our ultraviolet photoelectron spectroscopy (UPS) experiments, we find that the use of a hybrid functionals is necessary to obtain the correct order of the electronic states.

Original languageEnglish
Pages (from-to)2969-2992
Number of pages24
JournalMolecules
Volume19
Issue number3
DOIs
StatePublished - Mar 2014
Externally publishedYes

Keywords

  • Band-Structure
  • Hybrid Functional
  • Metal/Organic Interface
  • Phthalocyanine
  • Quantum-Mechanical Simulation
  • Ultraviolet Photoelectron Spectroscopy
  • Van Der Waals Interaction

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