Regensburg 2007 – wissenschaftliches Programm
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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices
SYOE 4: Organic Transistors
SYOE 4.5: Vortrag
Dienstag, 27. März 2007, 11:00–11:15, H1
Reduced contact and sheet resistance in bottom-contact pentacene field-effect transistors using palladium electrodes — •D. V. Pham1, G. Deck1, C. Bock1, U. Kunze1, D. Käfer2, G. Witte2, and Ch. Wöll2 — 1Lehrstuhl für Werkstoffe und und Nanoelektronik, Ruhr-Universität Bochum, D-44780 — 2Lehrstuhl für Physikalische Chemie I, Ruhr-Universität Bochum, D-44780
The influence of the source and drain contact metals (Au, Pd, and Pt) on the morphology and on the OFET performance was investigated. The devices consisted of metal source and drain electrodes contacting a 110-nm-thick pentacene film thermally deposited on SiO2 dielectrics (d = 40 nm) with an n+-doped Si substrate serving as the gate electrode. Transistors with channel lengths from L = 3 µ m to 100 µ m at a constant channel width w = 2 mm are prepared in order to separate the sheet resistance from the parasitic resistance of the contacts and leads. The contact resistance of transistors with Pd electrodes is four times smaller and the sheet resistance is eight times smaller than those of transistors with Pt or Au electrodes. The reduced sheet resistance is also reflected by a reduced trap density. Although Pt has a higher work function than Au and Pd the transistors with Au and Pt electrodes have similarly electrical characteristics. This can be explained by the film morphology. In order to study the nucleation of the pentacene on the OFET substrate further samples are prepared with an 8-nm-thick pentacene film. While the growth on the Au and Pt electrodes is completely different to the film morphology on silicon dioxide the growth on Pd is smiliarly to that on the insulator.