Fabrication and characterization of single-grain organic field-effect transistor of pentacene

A single-grain pentacene field-effect transistor with ordinary top-contact structure is fabricated, and its electrical properties are characterized at various temperatures. The device exhibits field-effect mobility as high as 2 cm(2)/V s at 300 K, although mobility is dependent on gate voltage. This value for field-effect mobility is about one order of magnitude higher than that of a polycrystalline device made from the same pentacene film. The activation energy obtained from an Arrhenius plot of mobility is nearly constant with varying gate voltage, whereas the activation energy of the polycrystalline device decreases as gate voltage increases. Such behavior of the activation energy suggests that intrinsic carrier transport in an organic grain can be described by thermally activated hopping of molecular polarons while extrinsic transport across grain boundaries can be described by the trap model. (C) 2004 American Institute of Physics.