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Fully Atomistic Understanding of the Electronic and Optical Properties of a Prototypical Doped Charge-Transfer Interface

DOI: 10.1021/acsnano.7b05828 DOI Help

Authors: Anu Baby (Institute of Solid State Physics, NAWI Graz, Graz University of Technology; University of Milano-Bicocca) , Marco Gruenewald (Friedrich Schiller University Jena) , Christian Zwick (Institute of Solid State Physics, Friedrich Schiller University Jena) , Felix Otto (Institute of Solid State Physics, Friedrich Schiller University Jena) , Roman Forker (Institute of Solid State Physics, Friedrich Schiller University Jena) , Gerben Van Straaten (Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich; Jülich Aachen Research Alliance (JARA)−Fundamentals of Future Information Technology) , Markus Franke (Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich; Jülich Aachen Research Alliance (JARA)−Fundamentals of Future Information Technology) , Benjamin Stadtmueller (University of Kaiserslautern; Graduate School of Excellence Materials Science in Mainz) , Christian Kumpf (Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich; Jülich Aachen Research Alliance (JARA)−Fundamentals of Future Information Technology) , Gian Paolo Brivio (University of Milano-Bicocca) , Guido Fratesi (University of Milano-Bicocca) , Torsten Fritz (Institute of Solid State Physics, Friedrich Schiller University Jena) , Egbert Zojer (Institute of Solid State Physics, NAWI Graz, Graz University of Technology)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Nano , VOL 11 , PAGES 10945-10508

State: Published (Approved)
Published: September 2017
Diamond Proposal Number(s): 10370

Abstract: The current study generates profound atomistic insights into doping-induced changes of the optical and electronic properties of the prototypical PTCDA/Ag(111) interface. For doping K atoms are used, as KxPTCDA/Ag(111) has the distinct advantage of forming well-defined stoichiometric phases. To arrive at a conclusive, unambiguous, and fully atomistic understanding of the interface properties, we combine state-of-the-art density-functional theory calculations with optical differential reflectance data, photoelectron spectra, and X-ray standing wave measurements. In combination with the full structural characterization of the KxPTCDA/Ag(111) interface by low-energy electron diffraction and scanning tunneling microscopy experiments (ACS Nano 2016, 10, 2365–2374), the present comprehensive study provides access to a fully characterized reference system for a well-defined metal–organic interface in the presence of dopant atoms, which can serve as an ideal benchmark for future research and applications. The combination of the employed complementary techniques allows us to understand the peculiarities of the optical spectra of K2PTCDA/Ag(111) and their counterintuitive similarity to those of neutral PTCDA layers. They also clearly describe the transition from a metallic character of the (pristine) adsorbed PTCDA layer on Ag(111) to a semiconducting state upon doping, which is the opposite of the effect (degenerate) doping usually has on semiconducting materials. All experimental and theoretical efforts also unanimously reveal a reduced electronic coupling between the adsorbate and the substrate, which goes hand in hand with an increasing adsorption distance of the PTCDA molecules caused by a bending of their carboxylic oxygens away from the substrate and toward the potassium atoms.

Journal Keywords: density-functional theory calculations; differential reflectance spectroscopy; doping; electronic structure; metal−organic interface; optical properties; X-ray standing wave

Subject Areas: Materials, Chemistry


Instruments: I09-Surface and Interface Structural Analysis