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Bilayer Formation vs Molecular Exchange in Organic Heterostructures: Strong Impact of Subtle Changes in Molecular Structure

DOI: 10.1021/acs.jpcc.8b01529 DOI Help

Authors: Qi Wang (Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University) , Antoni Franco-cañellas (Universität Tübingen) , Penghui Ji (Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University) , Christoph Buerker (Universität Tübingen) , Rong-bin Wang (Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University; Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin) , Katharina Broch (Institut für Angewandte Physik, Universität Tübingen) , Pardeep Kumar Thakur (Diamond Light Source) , Tien-lin Lee (Diamond Light Source) , Haiming Zhang (Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University) , Alexander Gerlach (Universität Tübingen) , Lifeng Chi (Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University) , Steffen Duhm (Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University) , Frank Schreiber (Institut für Angewandte Physik, Universität Tübingen)
Co-authored by industrial partner: No

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

State: Published (Approved)
Published: April 2018
Diamond Proposal Number(s): 10443

Abstract: Organic heterostructures are a central part of a manifold of (opto)electronic devices and serve a variety of functions. Particularly, molecular monolayers on metal electrodes are of paramount importance for device performance as they allow tuning energy levels in a versatile way. However, this can be hampered by molecular exchange, i.e., by interlayer diffusion of molecules toward the metal surface. We show that the organic–metal interaction strength is the decisive factor for the arrangement in bilayers, which is the most fundamental version of organic–organic heterostructures. The subtle differences in molecular structure of 6,13-pentacenequinone (P2O) and 5,7,12,14-pentacenetetrone (P4O) lead to antithetic adsorption behavior on Ag(111): physisorption of P2O but chemisorption of P4O. This allows providing general indicators for organic–metal coupling based on shifts in photoelectron spectroscopy data and to show that the coupling strength of copper-phthalocyanine (CuPc) with Ag(111) is in between that of P2O and P4O. We find that, indeed, CuPc forms a bilayer when deposited on a monolayer P4O/Ag(111) but molecular exchange takes place with P2O, as shown by a combination of scanning tunneling microscopy and X-ray standing wave experiments.

Subject Areas: Materials, Chemistry, Physics


Instruments: I09-Surface and Interface Structural Analysis