Tuesday, May 01, 2012

Chemical Wiring and Soldering toward All-Molecule Electronic Circuitry

Chemical Wiring and Soldering toward All-Molecule Electronic Circuitry
By: Omar Gómez Rojas ID:139236

Now, Yuji Okawa of the National Institute for Materials Science in Tsukuba, Japan, and colleagues have developed a method to wire and bond single molecules. Okawa's group starts with a monomolecular film of a diacetylene on a graphite substrate. The researchers then deposit a small amount of phthalocyanine, which forms nanoclusters on the surface. Finally, the researchers bring the tip of a scanning tunnelling microscope to one of the phthalocyanine molecules and, applying a pulsed voltage across the tip and surface, initiate chain polymerisation of the diacetylene. This forms a polymer nanowire that bonds to the phthalocyanine molecule.

Key to single-molecule electronics is connecting functional molecules to each other using conductive nanowires. This involves two issues: how to create conductive nanowires at designated positions, and how to ensure chemical bonding between the nanowires and functional molecules. Here, we present a novel method that solves both issues. Relevant functional molecules are placed on a self-assembled monolayer of diacetylene compound. A probe tip of a scanning tunneling microscope is then positioned on the molecular row of the diacetylene compound to which the functional molecule is adsorbed, and a conductive polydiacetylene nanowire is fabricated by initiating chain polymerization by stimulation with the tip. Since the front edge of chain polymerization necessarily has a reactive chemical species, the created polymer nanowire forms chemical bonding with an encountered molecular element. We name this spontaneous reaction “chemical soldering”. First-principles theoretical calculations are used to investigate the structures and electronic properties of the connection. We demonstrate that two conductive polymer nanowires are connected to a single phthalocyanine molecule. A resonant tunneling diode formed by this method is discussed.

Chemical Wiring and Soldering toward All-Molecule Electronic Circuitry
Yuji Okawa, Swapan K. Mandal, Chunping Hu, Yoshitaka Tateyama, Stefan Goedecker, Shigeru Tsukamoto, Tsuyoshi Hasegawa, James K. Gimzewski, and Masakazu Aono
J. Am. Chem. Soc., 2011, 133 (21), pp 8227–8233
DOI: 10.1021/ja111673x

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