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Studies from Columbia University Yield New Information about General Science (Charge transport and rectification in molecular junctions formed with...

September 5, 2014



Studies from Columbia University Yield New Information about General Science (Charge transport and rectification in molecular junctions formed with carbon-based electrodes)

By a News Reporter-Staff News Editor at Science Letter -- Researchers detail new data in Science. According to news reporting out of New York City, New York, by NewsRx editors, research stated, "Molecular junctions formed using the scanning-tunneling-microscope-based break-junction technique (STM-BJ) have provided unique insight into charge transport at the nanoscale. In most prior work, the same metal, typically Au, Pt, or Ag, is used for both tip and substrate."

Our news journalists obtained a quote from the research from Columbia University, "For such noble metal electrodes, the density of electronic states is approximately constant within a narrow energy window relevant to charge transport. Here, we form molecular junctions using the STM-BJ technique, with an Au metal tip and a microfabricated graphite substrate, and measure the conductance of a series of graphite/amine-terminated oligophenyl/Au molecular junctions. The remarkable mechanical strength of graphite and the single-crystal properties of our substrates allow measurements over few thousand junctions without any change in the surface properties. We show that conductance decays exponentially with molecular backbone length with a decay constant that is essentially the same as that for measurements with two Au electrodes. More importantly, despite the inherent symmetry of the oligophenylamines, we observe rectification in these junctions. State-of-art ab initio conductance calculations are in good agreement with experiment, and explain the rectification. We show that the highly energy-dependent graphite density of states contributes variations in transmission that, when coupled with an asymmetric voltage drop across the junction, leads to the observed rectification."

According to the news editors, the research concluded: "Together, our measurements and calculations show how functionality may emerge from hybrid molecular-scale devices purposefully designed with different electrodes beyond the so-called 'wide band limit,' opening up the possibility of assembling molecular junctions with dissimilar electrodes using layered 2D materials."

For more information on this research see: Charge transport and rectification in molecular junctions formed with carbon-based electrodes. Proceedings of the National Academy of Sciences of the United States of America, 2014;111(30):10928-10932. Proceedings of the National Academy of Sciences of the United States of America can be contacted at: Natl Acad Sciences, 2101 Constitution Ave NW, Washington, DC 20418, USA. (National Academy of Sciences - www.nasonline.org/; Proceedings of the National Academy of Sciences of the United States of America - www.nasonline.org/publications/pnas/)

Our news journalists report that additional information may be obtained by contacting T. Kim, Columbia University, Dept. of Phys, New York, NY 10027, United States. Additional authors for this research include Z.F. Liu, C. Lee, J.B. Neaton and L. Venkataraman (see also Science).

Keywords for this news article include: Science, New York City, United States, North and Central America

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


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Source: Science Letter


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