MOLECULAR ELECTRONICS
SEEING IS BELIEVING STM technique lets single-molecule junction be prepared and
imaged
MITCH
JACOBY
If a picture is worth a
thousand words, then scientists' grasp of molecular electronics has
just been expanded by a grand quantity. Researchers at the
University of California, Irvine, have recorded the first direct
image of a small molecule confined between two metal contacts and
have probed its electronic structure systematically, revealing much
information about the microscopic junction.
The potential of extremely fast and ultradense
electronics based on single molecules as circuit components has
motivated many research groups to study the electronic properties of
individual molecules. Several teams have created tiny structures
that hold a single molecule in a nanometer-sized gap between
electrical leads and probed the trapped molecule's electronic
conductivity.
But typically, such studies cannot answer
unambiguously various questions about the structure and nature of
the junction. For example, how does the molecule bond to the metal
contacts? Is it attached to both leads? What is its orientation? And
what effect does the metal have on the molecule's
properties?
UC Irvine physics and chemistry professor Wilson
Ho and coworkers have now used a scanning tunneling microscope
to position a copper phthalocyanine molecule in the gap between two
gold contacts that they constructed one atom at a time. They then
recorded high-resolution images of the junction
[Science, published online Sept. 4, http://www.sciencemag.org/cgi/content/abstract/1088971v1].
In addition, by altering the length of the gold
leads on an atomic scale, the Irvine team was able to study the
effect of the metal on the system's electronic density of
states.
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PICTURE THIS With
atomic-scale dexterity, UC Irvine scientists have used a
scanning tunneling microscope to place a copper
phthalocyanine molecule between tiny gold leads and to
image the
bridge. | |