electronics--using molecules in the construction
of electronic circuitry--using molecules in the construction
of electronic circuitry--just took a significant
step closer to reality. Principal investigator Dr.
Robert Wolkow, postdoctoral fellow Dr. Paul Piva
and a team of researchers from the University of
Alberta and the National Institute for Nanotechnology
of the National Research Council have designed and
tested a new concept for a single molecule transistor.
They have shown, for the first time, that a single
charged atom on a silicon surface can regulate the
conductivity of a nearby molecule. Their breakthrough
will be published in the June 2, 2005 edition of
the scientific journal Nature .
Miniaturization of microelectronics has a finite
end based on today's technology. A new concept to
circumvent the limits of conventional transistor
technology was needed. The authors conducted an experiment
to examine the potential for electrical transistors
on a molecular scale. Their approach has solved what
has been an insurmountable hurdle to making a molecular
device--getting connections onto a single molecule.
They demonstrated that a single atom on a silicon
surface can be controllably charged, while all surrounding
atoms remain neutral. A molecule placed adjacent
to that charged site is 'tuned', which allows electrical
current to flow through the molecule from one electrode
to another. The current flowing through the molecule
can be switched on and off by changing the charge
state of the adjacent atom.
We have shown the potential for devices of unheard-of
smallness and unheard-of efficiency. says Dr. Wolkow. A
technology based on this concept would require much
less energy to power, would produce much less heat,
and run much faster.
Molecules are exceedingly small, on the scale of
a nanometre (one billionth of a metre). Wolkow's
team solved the connection problem by using the electrostatic
field emanating from a single atom to regulate the
conductivity of a molecule, allowing an electric
current to flow through the molecule. These effects
were easily observed at room temperature, in contrast
to previous molecular experiments that had to be
done at temperatures close to absolute zero in order
to measure a conductivity change. Another significant
aspect of this breakthrough is the fact that only
one electron from the atom is needed to turn molecular
conductivity on or off. On a conventional transistor,
this gating action requires about one million electrons.
concept could circumvent the limits of conventional
transistor technology and permit miniaturization
on a nanometric scale. Better...faster...cheaper--that's
the promise of molecular electronics. In our case,
we also have a potentially powerful green technology
because of its minimal power and material requirements,
and the biodegradable nature of the device."
says that although his results represent a key
step toward molecular electronics, more steps are
required. He advocates doing research on hybrid
molecular/silicon devices. "This way, we can piggyback
on all the great capacity that has already been established
for silicon, and just supplement it. Our prototype
works on silicon--thus allowing the old technology
to merge with the new."
am optimistic that molecular electronic devices
can be made using our method because I don't see
a reason why the remaining hurdles can't be overcome.
And given the promise of such devices--great speed,
small size, and high efficiency--the hurdles are
definitely worth tackling."
DETAILS OF PUBLICATION
Field Regulation of Single Molecule Conductivity by a Charged Surface Atom
Nature, 02 June 2005
Paul G. Piva1,2, Gino A. DiLabio2, Jason L. Pitters2,
Mohamed Rezeq1,2, Stanislav Dogel1, Werner A. Hofer3 & Robert
1Department of Physics, University of Alberta, Edmonton, Alberta, Canada
2National Institute for Nanotechnology, National Research Council of Canada,
Edmonton, Alberta, Canada
3Surface Science Research Centre, University of Liverpool, Liverpool, UK
The following funding acknowledgements from the
authors appear at the end of the paper:
Funding has been provided by iCORE, the NRC, the NSERC, CFI, the University
of Alberta and CIAR.
Illustrations, photos of authors, lab photos and
biographical information are available.