Berlin 2005 – wissenschaftliches Programm
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SYOO: Organic Optoelectronics and Photonics
SYOO 6: Poster
SYOO 6.40: Poster
Montag, 7. März 2005, 18:00–20:00, Poster TU A
Correlation of the OFET mobility and the morphology of pentacene films grown on alumina films — •Michael Voigt and Moritz Sokolowski — Institut für Physikalische und Theoretische Chemie, Universität Bonn, Wegelerstrasse 12, 53115 Bonn
Organic field effect transistors (OFETs) were fabricated by evaporation of pentacene (Pc) onto alumina insulator films. The alumina films were prepared on ITO covered glass (gate) by rf magnetron sputtering. Source and drain contacts (Au; channel length L = 30 - 80 µm) were made by shadow mask technique on top of the Pc films. The Pc films have been deposited at various evaporation rates (r = 1 - 10 nm/min) at several substrate temperatures (T = -17 - 90∘C). Investigations by AFM and polarization light (video) microscopy reveal that the morphology of the Pc films depends strongly on T and r. In the kinetic regime (low T, high r) the films are closed whereas in the thermodynamic regime (high T, low r) isolated crystallites are observed. The shape of the crystallites is either dendritic (for low T) or granular (for high T). The closed films show hole mobilities µ of 0.007 - 0.18 cm2/Vs (highest µ for T = 23∘C) whereas for isolated crystallites no µ could be measured. This work is supported by the DFG through the priority program "Organic Field Effect Transistors".