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Molecular electronics (sometimes called moletronics) is the use of molecules as wires and other components in the construction of electronic circuitry. The concept has been controversial -- initially because the conventional electrical resistance of a wire with a molecular-scale cross-section should be enormous, making electrical conductivity impossible.
Molecular electronics is often used in science fiction to explain why so much usefulness can be packed into so small a space. It is considered as a possible physical limit to Moore's Law as well as a solution to problems with making small-scale conventional silicon integrated circuits even smaller.
History
Study of charge transfer in molecules was advanced in the 1940s by Robert Mulliken and Albert Szent-Gyorgi in discussion of so-called "donor-acceptor" systems and developed the study of charge transfer and energy transfer in molecules.
Perhaps the first theoretical proof of molecular electronics for devices came from a 1974 paper from Mark Ratner and Avi Aviram, illustrating a molecular rectifier. Later, Aviram detailed a single-molecule field-effect transistor in 1988. Further concepts were proposed by Forrest Carter of the Naval Research Laboratory, including single-molecule logic gates.
Recent Breakthroughs
Recent progress in nanotechnology and nanoscience have facilitated both experimental and theoretical study of molecular electronics. In particular, the development of the scanning tunneling microscope (STM) and later the atomic force microscope (AFM) have facilitated manipulation of single-molecule electronics.
A collaboration of researchers at HP and UCLA, led by James Heath, Fraser Stoddart, R. Stanley Williams, and Philip Kuekes, has developed molecular electronics based on rotaxanes and catenanes.
Work is also being done on the use of single-wall carbon nanotubes as field-effect transistors. Most of this work is being done by IBM.
The Aviram-Ratner model for a molecular rectifier, which until recently was entirely theoretical, has been confirmed experimentally and unambiguously in a number of experiments by a group led by Geoffrey J. Ashwell at Cranfield University, UK. Many rectifying molecules have so far been identified, and the number and efficiency of these systems is expanding rapidly.
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