Electrical characterization of single grain and single grain boundary of pentacene thin film by nano-scale electrode array

Organic thin film transistors (O-TFTs) are attracting attentions recently for their possible application to flexible field effect transistor (FET) devices and even for candidate devices in post-silicon information systems. However, the organic thin films usually grow in a polycrystalline state, and the electrical properties are very difficult to set at an appropriate value because orientation and size of the polycrystalline grains are almost uncontrollable. Thus, it should be necessary to clarify the conduction characteristics within the single grain and between the grains through grain boundaries in order to precisely control the electrical properties of the organic thin films. This paper reports on a nano-scale electrode array, which provides a method to characterize single organic semiconductor grain, as well as to determine the single grain boundary effect on the electrical conduction. The fabrication method of the nano-scale electrode array and evaluation results are described. Single grain and single grain boundary in MBE grown pentacene thin film were detected and were measured for the first time using FET structures. The resistance of single grain was estimated to be around 10 M Ohms while that of single grain boundary to be about 100 M Ohms. This is the first experimental verification of the resistance of single grain pentacene thin film and single pentacene grain boundary.