Molecular-scale transistors based on self-assembled monolayers

The 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. However, most of the previous work has been focused on two-terminal devices. In contrast to that, three-terminal devices, i.e. transistors, could offer several advantages for logic operations, the most important being ´gain´. Recently, we demonstrated the possibility to modulate the conductance through a single molecular layer (∼10-20 Å) and even single active molecules by a third gate electrode (J.H. Schon et al., Adv. Mater. vol. 14, p. 232, 2002). Moreover, significant gain can be achieved in such devices at room temperature and has been achieved for approximately 15 molecules. In order to identify the switching mechanism we studied the charge transport through single benzene-1,4-dithiolate molecules embedded in an inert matrix of insulating alkanethiol molecules in a vertical three-terminal device structure.