03 Fakultät Chemie
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/4
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Item Open Access Highly ordered LB films of DHAP : a donor acceptor substituted polyene(1993) Schmelzer, Michael; Roth, Siegmar; Niesert, Claus-Peter; Effenberger, Franz; Li, Rui ChengThe donor acceptor substituted polyene 5-(4-dihexadecylaminophenyl)-2-methyl-2,4-pentadienal (DHAP) is - due to its amphiphilic nature - a promising candidate for the Langmuir-Blodgett (LB) technique. The molecule was studied as a monolayer on a pure water surface under argon atmosphere. Monolayers and multilayers were transfered onto solid support. The films showed a high degree of order in the monolayer as well as in thick multilayers. LB films were investigated with polarisation dependent UV/VIS absorption spectroscopy. The film spectra showed additional absorption peaks which were not present in the spectra of the molecules in solution. The relative peak intensities were highly dependent on the orientation of the electric field vector with respect to the substrate normal. To get a detailed picture of the arrangement of the films on the molecular level, we studied the polarisation dependence of the FTIR spectra in different experimental set-ups. The spectra showed a perpendicular orientation of the conjugated system with respect to the substrate, whereas the backbone of the saturated hydrocarbon chains showed a medium tilt angle of 20.0° with respect to the substrate normal. X-ray small angle diffraction measurements were applied to investigate the thickness of the LB layers. From the position of the Bragg peaks, a thickness of 5.45 nm per bilayer can be calculated, in agreement with a bilayer model showing different molecular alignment of the molecules transferred during upstroke and downstroke.Item Open Access Shape control in wafer-based aperiodic 3D nanostructures(2014) Jeong, Hyeon-Ho; Mark, Andrew G.; Gibbs, John G.; Reindl, Thomas; Waizmann, Ulrike; Weis, Jürgen; Fischer, PeerControlled local fabrication of three-dimensional (3D) nanostructures is important to explore and enhance the function of single nanodevices, but is experimentally challenging. We present a scheme based on e-beam lithography (EBL) written seeds, and glancing angle deposition (GLAD) grown structures to create nanoscale objects with defined shapes but in aperiodic arrangements. By using a continuous sacrificial corral surrounding the features of interest we grow isolated 3D nanostructures that have complex cross-sections and sidewall morphology that are surrounded by zones of clean substrate.Item Open Access Optimizing the plasma oxidation of aluminum gate electrodes for ultrathin gate oxides in organic transistors(2021) Geiger, Michael; Hagel, Marion; Reindl, Thomas; Weis, Jürgen; Weitz, R. Thomas; Solodenko, Helena; Schmitz, Guido; Zschieschang, Ute; Klauk, Hagen; Acharya, RachanaA critical requirement for the application of organic thin-film transistors (TFTs) in mobile or wearable applications is low-voltage operation, which can be achieved by employing ultrathin, high-capacitance gate dielectrics. One option is a hybrid dielectric composed of a thin film of aluminum oxide and a molecular self-assembled monolayer in which the aluminum oxide is formed by exposure of the surface of the aluminum gate electrode to a radio-frequency-generated oxygen plasma. This work investigates how the properties of such dielectrics are affected by the plasma power and the duration of the plasma exposure. For various combinations of plasma power and duration, the thickness and the capacitance of the dielectrics, the leakage-current density through the dielectrics, and the current–voltage characteristics of organic TFTs in which these dielectrics serve as the gate insulator have been evaluated. The influence of the plasma parameters on the surface properties of the dielectrics, the thin-film morphology of the vacuum-deposited organic-semiconductor films, and the resulting TFT characteristics has also been investigated.