Self-assembled monolayer organic field-effect transistors

Abstract

The use of individual molecules as functional electronic devices was proposed in 1974 (ref. 1). Since then, advances in the field of nanotechnology have led to the fabrication of various molecule devices and devices based on monolayer arrays of molecules. Single molecule devices are expected to have interesting electronic properties, but devices based on an array of molecules are easier to fabricate and could potentially be more reliable. However, most of the previous work on array-based devices focused on two-terminal structures: demonstrating, for example, negative differential resistance, rectifiers, and re-configurable switching. 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, that is, transistors, could offer several advantages for logic operations compared to two-terminal switches, the most important of which is 'gain'-the ability to modulate the conductance. Here, we demonstrate gain for electronic transport perpendicular to a single molecular layer ( approximately 10-20 A) by using a third gate electrode. Our experiments with field-effect transistors based on self-assembled monolayers demonstrate conductance modulation of more than five orders of magnitude. In addition, inverter circuits have been prepared that show a gain as high as six. The fabrication of monolayer transistors and inverters might represent an important step towards molecular-scale electronics.

Transport in molecular transistors: Symmetry effects and nonlinearities

“…1 Some molecules can operate as diodes, 2 Coulomb blockade structures, 3 or switching devices with high negative differential resistance at room temperature. 4,5 Transistorlike behavior in molecular three-terminal devices ͑molecular transistors͒ has been demonstrated in a single C 60 fullerene connected to gold electrodes, 6 in organic self-assembled monolayers, 7 and in single-and multiwalled carbon nanotubes. 8,9 The source-drain current in these systems ͑three-terminal devices͒ is controlled by a gate voltage.…”

Charge transfer in molecular conductors—oxidation or reduction?

“…This is an issue that clearly needs a lot more attention, since the precise location of E F depends on the model for the contacts, as well as the method of calculating the molecular Hamiltonian. A third terminal (gate) [8] can help resolve some of these issues. One of the consequences of a self-consistent evaluation of energy levels is that as we raise the fermi energy, the levels float up by an amount equal to the charging energy (for a solid, this is roughly given by the capacitance of a sphere of radius equal to the size of the electronic wave function).…”

Combinatorial optimization problems in self-assembly

“…Lopinski et al [11] have demonstrated the self-assembly of molecular silicon structures. And, most recently, Bell Labs has announced the construction, by selfassembly, of the world's first molecular-thickness transistor [19].…”