Unimolecular rectifiers: methods and challenges.
ABSTRACT Six unimolecular rectifiers have been studied at the University of Alabama: Langmuir-Blodgett (LB) or Langmuir-Schaefer (LS), or self-assembled monolayers of these molecules show asymmetric electrical conductivity between Au or Al electrodes. These molecules are gamma-hexadecylquinolinium tricyanoquinodimethanide (Fig. 1, 2), 2,6-di[dibutylamino-phenylvinyl]-l-butylpyridinium iodide, 3, dimethylanilino-aza[C60]-fullerene, 4, fullerene-bis-[4-diphenylamino-4''-(N-ethyl-N-2-ethyl)-amino-1,4-diphenyl-1,3 -butadiene] malonate, 5, N-(10-nonadecyl)-N-(2-ferrocenyl-ethyl)-pyrenyl-methyl)pery-lene-3,4,9,10-bis(dicarboxyimide), 6, and 4,5-dipentyl-5'-methyltetrathiaful-valen-4'-methyl-oxy-2,4,5-trinitro-9-dicyanomethylenefluorene-7-(3-sulfonylpropionate), 7. Many ancillary experiments must be performed before unimolecular rectification can be fully understood. This review will focus on the fabrication techniques and the analytical tools that can help understand the asymmetric current-voltage (IV) curves. These tools include molecular orbital calculations, cyclic voltammetry, ultraviolet photoelectron spectroscopy, scanning tunneling microscopy, contact angle goniometry, ultraviolet-visible-near-infrared spectroscopy, grazing-angle Fourier transform infrared spectroscopy, surface plasmon resonance, spectroscopic ellipsometry, grazing-incidence X-ray reflectometry, core-level and valence-band X-ray photoelectron spectroscopy.
Article: Unimolecular electronics[Show abstract] [Hide abstract]
ABSTRACT: 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.Journal of Materials Chemistry 11/2008; 18(37). · 6.63 Impact Factor
- Bulletin of The Chemical Society of Japan - BULL CHEM SOC JPN. 01/2008; 81(7):869-884.
- Bulletin of The Chemical Society of Japan - BULL CHEM SOC JPN. 01/2008; 81(11):1492-1499.