Self-assembled monolayer organic field-effect transistors

The use of individual molecules as functional electronic devices was propos ed in 1974 (ref. 1). Since then, advances in the field of nanotechnology ha ve led to the fabrication of various molecule devices and devices based on monolayer arrays of molecules(2-11). Single molecule devices are expected t o have interesting electronic properties, but devices based on an array of molecules are easier to fabricate and could potentially be more reliable. H owever, most of the previous work on array-based devices focused on two-ter minal structures: demonstrating, for example, negative differential resista nce(8), rectifiers(9), and re-configurable switching(10,11). It has also be en proposed that diode switches containing only a few two-terminal molecule s could be used to implement simple molecular electronic computer logic cir cuits(12). However, three-terminal devices, that is, transistors, could off er several advantages for logic operations compared to two-terminal switche s, the most important of which is 'gain'-the ability to modulate the conduc tance. Here, we demonstrate gain for electronic transport perpendicular to a single molecular layer (similar to 10-20 Angstrom) by using a third gate electrode. Our experiments with field-effect transistors based on self-asse mbled monolayers demonstrate conductance modulation of more than five order s of magnitude. In addition, inverter circuits have been prepared that show a gain as high as six. The fabrication of monolayer transistors and invert ers might represent an important step towards molecular-scale electronics.