Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 54: Joint Session: Organic Semiconductors IV: Excitations and Charges
HL 54.8: Vortrag
Mittwoch, 16. März 2011, 16:15–16:30, ZEU 222
Investigation of single grains in nanoscale P3HT OFETs — •Dileep Dhakal, Steve Pittner, Torsten Balster, and Veit Wagner — School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen
Regio-regular poly(3-hexylthiophene) (P3HT) has a chain length in the range of several nm up to more than 100 nm, depending on the molecular weight. In addition, the lateral correlation length of 50 nm thick spin-coated P3HT-layers was found to be 150 nm [1] corresponding to the range of structural order within the film. Therefore, the reduction of the channel length L in organic field effect transistors towards the sub-100 nm range will open up the possibility for channels formed by single grains or individual P3HT chains. For this investigation transistor templates on oxidized silicon substrates are prepared by 2 approaches i) by electron beam lithography (EBL) and ii) by metal deposition under defined tilt angle at a preexisting contact edge. The resulting channel length between the source and drain electrode is in the range from 1 µm to 100 nm for EBL and reaches even lower channel sizes using the second approach. At L = 1 µm a mobility of 10−2 cm2/Vs is typically extracted from transfer curve measurements. Without optimization of the gold/P3HT-interface we find a decrease of mobility by more than one order of magnitude for 100 nm devices, which is attributed to an increased influence of the contact resistance. The ratio can be clearly improved by optimizing the interface. [1] B. Gburek and V. Wagner, Org. Electronics 11 (2010) 814.