An essential part of the device functionality in organic thin film transistors based on small molecules is the morphology of the semiconductor determined by the dielectric/semiconductor interface. A deep understanding and an intense control of the deposition parameters during the evaporation process of the active layer are required, where especially the initial stages of film growth determine the whole quality of the device. In this context, a smooth and trap-free dielectric surface with adapted surface energy is inevitable. Structuring processes requiring a lift-off procedure such as nanoimprint lithography (NIL) always result in manifold contamination of the affected interfaces due to chemical residua, physical impacts and increased surface roughness. All these defects prohibit satisfactory structural order of the semiconductor molecules and therefore lead to degradation of all critical device parameters. To optimise the growth and functionality of the active layer in NIL-processed organic thin film transistors, a detailed investigation of the influence of the semiconductor morphology and charge carrier transport mechanisms on the dynamic behaviour of the device is recommended. The interplay between theoretical device simulations and temperature dependent measurements of critical parameters in organic thin films transistors fabricated by NIL should establish the basis for the development of suitable growth priming procedures. Conceivable processes for adapting the interface properties are the deposition of compatible self-assembled monolayers as well as surface treatments of channel and contact regions of the thin film transistor.
|Tatsächlicher Beginn/ -es Ende||1/04/08 → 31/03/11|