Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 5: Organic-Inorganic Hybrid Systems and Organic Films I

O 5.1: Vortrag

Montag, 20. März 2017, 10:30–10:45, WIL A317

The Impact of Doping on the Interface Structure and Level Alignment of ZnO/F6TCNNQ Interfaces from First Principles — •Simon Erker and Oliver T. Hofmann — Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Austria

In inorganic/organic heterostructures the interface decisively determines the performance of a device. However, in particular for materials such as ZnO, which is commonly employed in organic electronics, the surface composition is often not well known. Indeed, experimentally the polar (000-1) surface shows a wide variety of different structures, even under notionally similar conditions. Recent work indicates that doping, that is often not systematically controlled, may be responsible for the observed diversity. However, so far a theoretical verification was impeded by the lack of a computational first-principles approach that allows dealing with long-ranged band bending and charged surfaces. We present an extension of the recently introduced charged-reservoir electronic sheet technique (CREST) [PRB 91, 075311 (2015)] to incorporate band-bending effects directly into our calculations. Using DFT in combination with ab-initio thermodynamics we determine a doping dependent surface phase diagram of O-terminated ZnO. We find that the surface preferably adsorbs hydrogen to achieve a stable surface, but that its coverage becomes smaller with increasing doping concentration. We proceed to show how the different surface terminations and the corresponding band-bending affects the level alignment and the adsorption energy for the deposition of the strong electron acceptor F6TCNNQ.