Abstract:

Manufacturing organic field effect transistors (OFETs) from single crystals requires complex procedures for preparation of single crystals and their alignment at the exact right position. This is in contrast to the ease of fabrication of organic thin film transistors (OTFTs) through either spin coating, printing, or various evaporation methods. There have been a great deal of research in single crystal transistors as it offers high mobility and better device performance and stability due to less defects and grain boundaries than the thin films. Here we demonstrate a new type of transistor which can be prepared with similar ease as thin films but is based on collective use of single crystals. The fabrication is carried out with the aid of stencils mask pattern to yield a device structure we call Organic single crystallites Statistical Field Effect Transistor (OSFET). The concept of the statistical FET (SFET) structure is to first grow many crystallites on gate dielectric such that they form a discontinuous poly crystalline layer of sizes smaller than the channel length and hence deposition of source-drain contacts shows no current. Through one additive step that deposits conducting round disks, over the entire area, the crystallites become inter-connected. In fact, the new device is now being composed of many transistors interconnected in series and in parallel. The odds that a given crystallite is being contacted on both sides and the number of crystallites connecting two conducting circles are a statistical issue and hence the name of this structure: statistical field-effect transistor (SFET).

Our results suggest that unlike single crystal transistors, OSFETs do not require tedious fabrication process, can be easily prepared with the aid of a single additive step.