Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 20: Organische Dünnschichten II
O 20.8: Vortrag
Samstag, 5. März 2005, 12:30–12:45, TU EB202
Transport in capped organic thin film transistors at elevated temperatures — •S. Meyer1, J. Wrachtrup1, J. Pflaum1, S. Sellner2, G. Ulbricht2, A. Gerlach3, F. Schreiber3, M. Fischer4, and B. Gompf4 — 1III. Physikalisches Institut, Universität Stuttgart — 2Max-Planck-Institut für Metallforschung, Stuttgart — 3Physical and Theoretical Chemistry Laboratory, Oxford University, UK — 4I. Physikalisches Institut, Universität Stuttgart
The thermal stability of the organic semiconducting layer is of crucial importance for the device performance in organic electronics. To address this problem we have performed comparative studies on organic thin film transistors (OTFTs) utilizing pentacene thin films with and without capping layer. The latter is realized by a 50nm thick sputter layer of aluminum oxide. On pentacene TFTs a field-effect is demonstrated up to temperatures of 2501exoC which is about 1701exoC above the desorption point of uncapped pentacene films on SiO2. From the TFTs characteristics a complex behavior of the temperature dependent hole mobility and threshold voltage can be deduced, indicating that the device operation at these elevated temperatures is predominantly limited by the transistor structure, i.e. metal-diffusion at the contacts, and not by the organic material. Detailed studies by thermal desorption spectroscopy and X-ray diffraction on capped pentacene and diindenoperylene thin films show that the organic layer remains crystalline far above the breakdown temperature of the TFTs as a function of heating rate, thickness and stoichiometry of the AlOx. capping layer [1].
[1] Sellner et al., Adv. Mat. 16 (2004) 1750