Berlin 2005 – scientific programme

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SYOO: Organic Optoelectronics and Photonics

SYOO 6: Poster

SYOO 6.36: Poster

Monday, March 7, 2005, 18:00–20:00, Poster TU A

Surface Potential profiling on operating full organic thin film transistors by Kelvin probe force microscopy — •Markus Geuß, Klaus Müller, Ioanna Paloumpa, and Dieter Schmeißer — BTU Cottbus, Lehrstuhl Angewandte Physik II/Sensorik, Universitätsplatz 3-4, 03044 Cottbus

Kelvin-AFM is employed to study all polymer organic thin film transistors which are promising candidates for low cost - low performance applications like active matrix displays, sensors or single-serving devices. We use bottom contact source-drain- electrode structures of different organic materials like carbon-black or graphite plotted on a printing foil. Semiconducting regioregular Poly(3-Hexylthiophene-2,5-diyl) (P3HT) was subsequently deposited by spin coating. Surface potential profiles across the transistor channel were measured by Kelvin-AFM for various source-drain potential differences and signs. We found that contact resistances cause characteristic steps in the surface potential near the channel edges which vary with the electrode material. Furthermore, nonlinearities appear in the potential gradient which possibly give evidence for lateral inhomogeneities of the carrier mobilities. In summary, surface potential imaging with high lateral resolution ( approx. 100 nm) is introduced as a powerful tool for the characterisation of the transistor performance and the selection of suitable low cost electrode materials.