Thermal annealing effects on morphology and electrical response in ultrathin film organic transistors

Ultra-thin organic film transistors were annealed in vacuum at constant temperature and for different time intervals. This treatment eliminates unintentional doping and reduces hysteresis in I/V curves, both for pentacene and alpha-sexithienyl, without substantially improving the charge mobility. Devices that originally exhibited high and non-ohmic contact resistance never matched the characteristics of devices with well grown electrode/semiconductor interfaces, even after annealing. Prolonging the annealing time resulted in film rupture due to either re-crystallization or molecular desorption. This process started before healing of molecular disorder at the relevant interfaces could take place. (C) 2004 Elsevier B.V. All rights reserved.