Charge transport in thin layers of organic crystals

Abstract

Recently, the organic thin layers have been studied widely due to their good properties for application in field-effect transistors. In this paper we survey recent studies on carrier transport properties in such molecular layers which are promising for applying in transistors. First we present the main electronic properties of organic molecules forming layers or crystals and the relation of this properties on specific features of band structure of organic crystals. The layers of pentacene are studied particularly as an example. The crystal structure of this material is presented. The experimental methods of carrier mobility measurements in high resistivty layers studied are described. The experimental results are in agreement with Visenberg model of charge transport in non-ordered materials. We discuss the charge transport properties measured for single crystal transistors. The mobility in these crystals is significantly greater in comparison with layers particularly at low temperatures and shows an interesting anisotropy in respect to crystallographic directions.