Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 23: POSTER Functional Organic Thin Films
CPP 23.19: Poster
Donnerstag, 30. März 2006, 17:00–19:00, P2
Electrical investigations on nanoscale oligothiophene transistors — •Arne Hoppe, Jörg Seekamp, Tobias Muck, Torsten Balster, and Veit Wagner — International University Bremen, Bremen, Germany
High transfer frequencies demand for nanoscale channel lengths combined with relatively high mobilities. Since contact properties seem to play an important role when downscaling the channel lengths of the device, materials have to be found, which show acceptable mobilities and good contact properties in short channels. Potential candidates are alkyl-substituted oligothiophenes. We showed already for micrometer-sized organic field-effect transistors (OFETs) that with growing number of thiophene rings the mobility increases. Channel lengths of interdigitated electrodes in the range from 40 µ m to below 50 nm, produced by e-beam lithography, were investigated. We used Dihexyl-n-thiophenes (DHnT) with n, the number of thiophene rings, ranging from four to seven as organic semiconductor. Organic molecular beam deposition (OMBD) in ultra-high vacuum was used to deposit the semiconductor onto the substrate at temperatures between 100 ∘C and 190 ∘C. The 40 µ m devices serve as a long channel reference point. Mobility values evaluated within the gradual channel approximation are as high as 0.11 cm2/(Vs) for the 40 µ m reference transistor. Lower mobilities were observed for smaller channel lengths. We found an increase in mobility with a higher number of thiophene rings for nanoscale channels. A model is presented to explain the correlation between mobility values, the length of the π-system and the channel length.