Unimolecular electronics

Appropriately chosen molecules (electron donors or acceptors) could replace doped inorganic semiconductors to form active electronic components. Ultimately, small electronic devices (<3 nm in all directions) may be the fastest possible electronic components, whose excited states would decay by photons, while comparably sized Si-based components must decay by phonons, and require huge heat dissipation. While the present and almost inexorable technological drive to make ever small circuits (Moore's “law”) may approach the 3 nm limit within ten years, molecules may present a very viable alternative to Si at that limit. The field of unimolecular or molecule-based electronics, conceived in 1973, has made huge progress towards unimolecular resistors, switches, rectifiers, negative differential resistance devices, and gain-less single-electron transistors. The challenge is to make reliable electrical contacts between inorganic electrodes and single molecules, and to improve calculations of intramolecular conductivity. Making an all-organic computer is the ultimate, if distant, goal.