Site-dependent charge transfer at the Pt(111)-ZnPc interface and the effect of iodine

• Published in: arXiv.org 2014-04
• Main Authors: Ahmadi, S, Agnarsson, B, Bidermane, I, Wojek, B M, Noël, Q, Sun, C H, Göthelid, M
• Format: Article
• Language: English
• Subjects: Attraction; Charge distribution; Charge transfer; Electronic structure; Iodine; Monolayers; Photoelectric emission; Photoelectrons; Platinum; Spectrum analysis; Substrates; Thick films; Thickness; X ray absorption; X ray photoelectron spectroscopy; Zinc
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1404.7832

The electronic structure of ZnPc, from sub-monolayers to thick films, on bare and iodated Pt(111) is studied by means of X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and scanning tunneling microscopy (STM). Our results suggest that at low coverage ZnPc lies almost parallel to the Pt(111) substrate, in a non-planar configuration induced by Zn-Pt attraction, leading to an inhomogeneous charge distribution within the molecule and charge transfer to the molecule. ZnPc does not form a complete monolayer on the Pt surface, due to a surface-mediated intermolecular repulsion. At higher coverage ZnPc adopts a tilted geometry, due to a reduced molecule-substrate interaction. Our photoemission results illustrate that ZnPc is practically decoupled from Pt, already from the second layer. Pre-deposition of iodine on Pt hinders the Zn-Pt attraction, leading to a non-distorted first layer ZnPc in contact with Pt(111)-I \(\left(\sqrt{3}\times\sqrt{3}\right)\) or Pt(111)-I \(\left(\sqrt{7}\times\sqrt{7}\right)\), and a more homogeneous charge distribution and charge transfer at the interface. On increased ZnPc thickness iodine is dissolved in the organic film where it acts as an electron acceptor dopant.