Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 5: Organic Thin Films

DS 5.2: Talk

Monday, February 25, 2008, 18:00–18:15, H 2013

Electronic properties of self-assembled organic monolayers on Ge surfaces — •Ian Sharp, Sebastian Schoell, Marco Hoeb, Martin S. Brandt, and Martin Stutzmann — Walter Schottky Institut, Technische Universität München, 85748 Garching, Germany

Ge surfaces and interfaces are commonly characterized by high densities of electrically active defect centers which severely limit the performance of Ge-based devices. Here, we investigate the electrical properties of metal-insulator-semiconductor (MIS) structures consisting of self-assembled alkyl monolayer-based insulating layers. Alkylation of the surface is achieved via thermal hydrogermylation of hydrogen terminated n-type (100) and (111) Ge with 1-octadecene, which is analogous to the well-known hydrosilylation reaction on Si. Chemical and structural characterization by thermal desorption spectroscopy (TDS), water contact angle measurements, and x-ray photoelectron spectroscopy (XPS) is performed and reveals covalently bound and tightly packed organic monolayers. Current-voltage (IV) measurements show strong rectifying behavior, although relatively large reverse bias saturation currents were observed. Capacitance-voltage (CV) measurements on both highly and nominally n-doped samples reveal Fermi-level pinning of functionalized surfaces at 0.2 eV below the conduction band edge. However, no slow-state charge trapping is observed and saturation capacitance behaviors are indicative of high quality insulating layers.