The pick-up stick transistor

We demonstrate an alternative path for achieving high transconductance organic transistors in spite of relatively large source to drain distances. The method is based on creating sub-percolating conducting networks either as a single layer composite or a bi-layer assembly. In the single layer composite, individual single wall carbon nanotubes (SWNT) and narrow ropes are dispersed in a soluble organic semiconducting host. The improvement of the electronic characteristic of such a scheme is equivalent to a 60-fold increase in mobility of the underlying organic semiconductor without reduction of the on/off ratio. In the semiconducting bi-layers pentacene is evaporated onto arrays of carbon nanotubes (SWNT) of varying connectivity. These field-induced sub-percolating networks allow an effective 10x reduction in source to drain distance that concurrent with a significant lowering in the pentacene crystallinity yields to a modest 2-5x increase in mobility without reduction in the on/off ratio. In both geometries, the majority of current paths between source and drain follow the metallic nanotubes but require a short, switchable serniconducting link to complete the circuit. (C) 2005 Elsevier Ltd. All rights reserved.