Regensburg 2022 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 40: Organic Molecules at Surfaces 4: Chemistry on Surfaces
O 40.5: Vortrag
Mittwoch, 7. September 2022, 11:30–11:45, S051
Control of overlayer-substrate coupling via alkali doping in two-dimensional metal-organic networks — •Billal Sohail1, Phil J. Blowey2, Tien-Lin Lee3, Paul T. P. Ryan3, David A. Duncan3, Giovanni Constantini1, D. Phil Woodruff1, and Reinhard J. Maurer1 — 1University of Warwick — 2University of Leeds — 3Diamond Light Source
We characterise a two-dimensional donor-acceptor network formed by coadsorption of alkali atoms and the prototypical acceptor molecule TCNQ (7,7,8,8-tetracyanoquinodimethane) at different orientations of Ag surfaces. We characterise the adsorption structure with a combi- nation of normal incidence x-ray standing wave (NIXSW) measure- ments, Scanning Tunnelling Microscopy, and dispersion-inclusive Den- sity Functional Theory, which we find to be in excellent agreement with experiment. The adsorption structure sensitively depends on an inter- play of molecule-metal charge transfer and long-range dispersion forces, which are influenced by the co-adsorption ratio between alkali atoms and TCNQ. In general, alkali atom co-adsorption reduces the molecule-substrate interaction strength, yet is energetically favoured compared to TCNQ co-adsorption with Ag adatoms. We show that the donor-acceptor ratio in the network is able to control the overlayer-substrate interaction, which strongly affects electronic properties such as the work function and the level alignment at the interface. Therefore, the concentration of alkali donor atoms can be used to tune electronic properties of the interface.