Self-Assembled Monolayer Organic Field-Effect Transistors

The use of individual molecules as functional electronic devices was proposed in 1974 and advances in the field of nanotechnology have led to various measurements of electrical properties on the molecular scale for both single molecule devices and devices based on a monolayer of an array of molecules. While single molecule devices are interesting, devices based on an array of molecules are easier to fabricate and could potentially be more reliable. However, most of this (the previous) work has been focusing on two-terminal devices, for example negative differential resistance, rectifiers, and re-configurable switching1. It has also been proposed that diode switches containing only a few two-terminal molecules could be used to implement simple molecular electronic computer logic circuits. However, three- terminal devices, i.e. transistors, could offer several advantages for logic operations compared to two-terminal switches, the most important of which being ‘gain'. Here, we demonstrate the possibility to modulate the conductance through a single molecular layer (~10-20 Å) by a third gate electrode. Our experiments with field-effect transistors based on self-assembled monolayers reveal a conductance modulation by more than five orders of magnitude. In addition, inverter circuits have been prepared showing a gain as high as six. The fabrication of monolayer transistors and inverters might represent an important step towards molecular scale electronics.