Morphology and Performance in Pentacene

Organic semiconductors for use in thin film insulated gate field effect transistors are discussed. The general structure and properties of this class of materials are presented, along with specific examples for the high performing organic semiconductor material pentacene. Several experiments attempting to correlate the morphology, performance, and effective trap density of pentacene with the deposition conditions were performed. Conditions varied were thickness, substrate temperature, and the placement of the electrodes. No correlation was found between any parameters and thickness or substrate temperature. The electrode placement correlated strongly with morphology and performance. In particular, the placement of electrodes onto the substrate before the pentacene halved the effective mobility and encouraged the formation of small grains in the channel. Finally, the use of high dielectric constant insulators for reducing the threshold voltage and improving the effective mobility at these small voltages was explored. A device produced using a room temperature process on a polycarbonate structure with a mobility of 0.27 cm 2/(Vs) at 5V was constructed. Thesis Supervisor: Akintunde I. Akinwande Title: Associate Professor of Electrical Engineering, MIT

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