Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Organic-Inorganic Hybrid Systems and Organic Films

O 45.25: Poster

Dienstag, 21. März 2017, 18:30–20:30, P1A

Dielectric properties of carbon nanomembranes prepared from aromatic self-assembled monolayers investigated by impedance spectroscopy — Paul Penner, Emanuel Marschewski, •Xianghui Zhang, and Armin Gölzhäuser — Faculty of Physics, University of Bielefeld, 33615 Bielefeld

Carbon nanomembranes (CNMs) are two-dimensional materials that are made by cross-linking self-assembled monolayers (SAMs) of aromatic molecules via low energy electron irradiation. Here we investigate the dielectric properties of pristine SAMs and CNMs with an EGaIn top electrode by impedance spectroscopy. Analysis and comparison of the tunneling resistance and capacitance density of pristine and cross-linked SAMs revealed a thickness dependent capacitance associated with the monolayer as well as a thickness independent capacitance. The latter could be attributed to the appearance of a new interface due to the decoupling of molecules from the underlying gold surface upon electron irradiation. We adopted an equivalent circuit to take into account the interfacial capacitance as well as the oxide layer of the EGaIn top electrode. An interfacial capacitance of about 5 fF/µm² was obtained for CNM-based molecular junctions. The tunneling decay constant β remains unaffected after electron irradiation, which exhibits a value of about 0.5 Å⁻¹ for both systems. Determination of dielectric constants of SAMs and CNMs from the impedance spectra will also be analyzed and discussed.