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Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 54: Organic Molecules on Inorganic Substrates III: Magnetism, Doping and Interfaces

O 54.9: Vortrag

Mittwoch, 3. April 2019, 12:30–12:45, H24

Critical Interplay of Atomic and Electronic Structure of Strong Electron Acceptors on Semiconductor Surfaces — •Haiyuan Wang1, Thorsten Schultz2, Sergey Levchenko1, Norbert Koch2, Matthias Scheffler1, and Mariana Rossi11Fritz Haber Insitute, Berlin, Germany — 2Humboldt University, Berlin, Germany

In organic-inorganic interfaces, it is necessary to understand how the atomic and electronic degrees of freedom cooperate or compete to yield the desired functional properties. Here, we address this issue first for strong electron acceptors (F4-TCNQ and F6-TCNNQ) adsorbed on H-Si(111). We perform systematic structure searches using density-functional theory with the HSE06 functional augmented by many-body van-der-Waals corrections. The results show that despite their similar composition, F4-TCNQ and F6-TCNNQ adsorb with significantly different geometries and show island formation propensities consistent with Volmer-Weber and Stranski-Krastanov growth modes, respectively. These densely-packed geometries induce a large interface-charge rearrangement, corresponding to a work-function (WF) increase of 1.11 eV for F4-TCNQ and 1.76 eV for F6-TCNNQ. Interestingly, vibrational fluctuations at room temperature produce a wide distribution of WF values, well modelled by a normal distribution with σ=0.17 eV [1]. Afterwards, we compare these results to the behavior of F6-TCNNQ on MoS2, where the origin of temperature-dependences in the charge transfer is discussed. This work is supported by the SFB-951 project. [1] H. Wang, et al., arXiv:1811.00037 (2018)

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