Organic Electronic Devices - Fundamentals, Applications, and Novel Concepts

This work addresses two substantial problems of organic electronic devices: the controllability and adjustability of performance, and the integration using scalable, high resolution patterning techniques for planar thin-film transistors and novel vertical transistor devices. Both problems are of particular importance for the success of transparent and flexible organic electronics in the future. To begin with, the static behavior in molecular doped organic pin-diodes is investigated. This allows to deduce important diode parameters such as the depletion capacitance, the number of active dopant states, and the breakdown field. Applying this knowledge, organic pin-diodes are designed for ultra-high-frequency applications and a cut-off-frequency of up to 1GHz can be achieved using optimized parameters for device geometry, layer thickness, and dopant concentration. The second part of this work is devoted to organic thin-film transistors, high resolution patterning techniques, as well as novel vertical transistor concepts. In particular, fluorine based photo-lithography, a high resolution patterning technique compatible to organic semiconductors, is introduced fielding the integration of organic thin-film transistors under ambient conditions. However, as it will be shown, horizontal organic thin-film transistors are substantially limited in their performance by charge carrier injection. Hence, down-scaling is inappropriate to enlarge the transconductance of such transistors. To overcome this drawback, a novel vertical thin-film transistor concept with a vertical channel length of ∼50nm is realized using fluorine based photo-lithography. These vertical devices can surpass the performance of planar transistors and hence are prospective candidates for future integration in complex electronic circuits

Cerebral differences in explicit and implicit emotional processing - An fMRI study

The processing of emotional facial expression is a major part of social communication and understanding. In addition to explicit processing, facial expressions are also processed rapidly and automatically in the absence of explicit awareness. We investigated 12 healthy subjects by presenting them with an implicit and explicit emotional paradigm. The subjects reacted significantly faster in implicit than in explicit trials but did not differ in their error ratio. For the implicit condition increased signals were observed in particular in the thalami, the hippocampi, the frontal inferior gyri and the right middle temporal region. The analysis of the explicit condition showed increased blood-oxygen-level-dependent signals especially in the caudate nucleus, the cingulum and the right prefrontal cortex. The direct comparison of these 2 different processes revealed increased activity for explicit trials in the inferior, superior and middle frontal gyri, the middle cingulum and left parietal regions. Additional signal increases were detected in occipital regions, the cerebellum, and the right angular and lingual gyrus. Our data partially confirm the hypothesis of different neural substrates for the processing of implicit and explicit emotional stimuli. Copyright (c) 2007 S. Karger AG, Basel

Orthopedic surgery increases atherosclerotic lesions and necrotic core area in ApoE-/- mice

Background and aims Observational studies show a peak incidence of cardiovascular events after major surgery. For example, the risk of myocardial infarction increases 25-fold early after hip replacement. The acuteness of this increased risk suggests abrupt enhancement in plaque vulnerability, which may be related to intra-plaque inflammation, thinner fibrous cap and/or necrotic core expansion. We hypothesized that acute systemic inflammation following major orthopedic surgery induces such changes. Methods ApoE−/− mice were fed a western diet for 10 weeks. Thereafter, half the mice underwent mid-shaft femur osteotomy followed by realignment with an intramedullary K-wire, to mimic major orthopedic surgery. Mice were sacrificed 5 or 15 days post-surgery (n = 22) or post-saline injection (n = 13). Serum amyloid A (SAA) was measured as a marker of systemic inflammation. Paraffin embedded slides of the aortic root were stained to measure total plaque area and to quantify fibrosis, calcification, necrotic core, and inflammatory cells. Results Surgery mice showed a pronounced elevation of serum amyloid A (SAA) and developed increased plaque and necrotic core area already at 5 days, which reached significance at 15 days (p = 0.019; p = 0.004 for plaque and necrotic core, respectively). Macrophage and lymphocyte density significantly decreased in the surgery group compared to the control group at 15 days (p = 0.037; p = 0.024, respectively). The density of neutrophils and mast cells remained unchanged. Conclusions Major orthopedic surgery in ApoE−/− mice triggers a systemic inflammatory response. Atherosclerotic plaque area is enlarged after surgery mainly due to an increase of the necrotic core. The role of intra-plaque inflammation in this response to surgical injury remains to be fully elucidated. © 2016 Elsevier Ireland Lt

Vertical organic permeable dual-base transistors for logic circuits

The main advantage of organic transistors with dual gates/bases is that the threshold voltages can be set as a function of the applied second gate/base bias, which is crucial for the application in logic gates and integrated circuits. However, incorporating a dual gate/base structure into an ultra-short channel vertical architecture represents a substantial challenge. Here, we realize a device concept of vertical organic permeable dual-base transistors, where the dual base electrodes can be used to tune the threshold voltages and change the on-currents. The detailed operation mechanisms are investigated by calibrated TCAD simulations. Finally, power-efficient logic circuits, e.g. inverter, NAND/AND computation functions are demonstrated with one single device operating at supply voltages of <2.0 V. We believe that this work offers a compact and technologically simple hardware platform with excellent application potential for vertical-channel organic transistors in complex logic circuits

Highly efficient modulation doping: A path toward superior organic thermoelectric devices

We investigate the charge and thermoelectric transport in modulation-doped large-area rubrene thin-film crystals with different crystal phases. We show that modulation doping allows achieving superior doping efficiencies even for high doping densities, when conventional bulk doping runs into the reserve regime. Modulation-doped orthorhombic rubrene achieves much improved thermoelectric power factors, exceeding 20 μW m−1 K−2 at 80°C. Theoretical studies give insight into the energy landscape of the heterostructures and its influence on qualitative trends of the Seebeck coefficient. Our results show that modulation doping together with high-mobility crystalline organic semiconductor films is a previosly unexplored strategy for achieving high-performance organic thermoelectrics

Politikszenarien für den Klimaschutz Band 3: Methodik-Leitfaden für die Wirkungsabschätzung von Maßnahmen zur Emissionsminderung

Die Bundesregierung hat sich im Jahr 1990 das Ziel gesetzt, den Ausstoß von Kohlendioxid in Deutschland bis zum Jahr 2005 gegenüber 1990 um 25 % zu reduzieren, und dieses Ziel mehrfach bekräftig. In den vergangenen Jahren sind bereits zahlreiche politische Maßnahmen zum Klimaschutz ergriffen worden und weitere Maßnahmen sind in der Planung oder werden derzeit noch diskutiert. Zur Bewertung der nationalen klimaschutzpolitischen Anstrengungen im Hinblick auf die Zielerreichung ist es erforderlich, daß die Wirkungen von bisherigen und weiteren Maßnahmen möglichst verläßlich quantifiziert werden können. Wirkungsanalysen von politischen Maßnahmen zum Klimaschutz sind auch Bestandteil der nationalen Berichtspflicht im Rahmen der Klimarahmenkonvention. Die entsprechenden Guidelines der FCCC "Policies and Measures" (Geneva, 17 July 1996) enthalten allgemeine Vorgaben zur Beschreibung der Maßnalunen und deren Wirkungen, die sektoral differenziert darzustellen sind. Die zugrunde liegenden Begriffe zur Kategorisierung von Maßnahmen und Wirkungen sind allerdings zum Teil nicht eindeutig definiert. Offen bleibt hierbei auch die Frage, mit welchen methodischen Verfahren die Wirkungen der Politik hinreichend genau geschätzt und einzelnen Maßnahmen zugerechnet werden können. Vor diesem Hintergrund hat das Umweltbundesamt (UBA) im Rahmen seines Umweltforschungsplanes das Forschungszentrum Jülich mit der Durchfuhrung eines Vorhabens "Politikszenarien für den Klimaschutz" beauftragt. Dabei sollten auch die Erkenntnisse und Instrumente aus dem vom BMBF geförderten IKARUS-Projekt$^{1}$ für die Berichterstattung der Bundesregierung und für Strategieüberlegungen im Rahmen der Klimarahmenkonvention nutzbar gemacht werden. Unter administrativer Koordination durch die Programmgruppe "Technikfolgenforschung" des Forschungszentrums Jülich (TFF) ist das Gesamtvorhaben vom Deutschen Institut für Wirtschaftsforschung (DIW), vom Fraunhofer-Institut für Systemtechnik und Innovationsforschung (ISI), von der Programmgruppe "Systemforschung und [...