Scientists Take Step Toward Molecular Electronics
- By William Jackson
- March 20, 2008
Researchers at the National Institute of Standards and Technology (NIST) have
built working electronic devices using a thin layer of organic molecules on
a traditional silicon platform, setting the stage for the next step toward practical
If advances in computing power and speed are to continue as they have in recent
decades, integrated circuits will have to break the size barrier presented by
traditional complementary metal-oxide semiconductors (CMOS).
Molecular electronics is one of the possible avenues for advancement. The NIST
research is being funded in part by the Defense Advanced Research Projects Agency.
"Molecules are the ultimate in scaling," said Curt Richter, lead
of NIST's Nanoelectronic Devices Metrology project and a member of the
team that built the tiny resistors. "They are not ready yet, but they
are the smallest thing mankind can engineer."
But for the engineering of practical molecular components, scientists would
have to work with existing commercial chip materials and manufacturing processes,
said Nadine Gergel-Hackett, a research associate at the National Research Center.
"If it is to be realized, the first step would be a hybrid" of silicon
substrate, typically used in CMOS, coupled with organic molecules.
But the traditional silicon crystal structure used in CMOS is "viewed
as not chemically friendly," Richter said. Because of this, little research
has been done with layering organic molecules onto them. So the team's
first job was to show it was possible to use common silicon substrates.
The team, which includes Gergel-Hackett, Curt Richter, L.J. Richter, C.D. Zangmeister
and C.A. Hacker, describe their work in a paper in the April issue of the Journal
of the American Chemical Society.
"We demonstrated that you can assemble the molecules just as well"
on the "technologically relevant" CMOS substrate as on specially
designed chip materials, Curt Richter said.
But is "just as well" good enough? "That's why we fabricated the devices,"
Gergel-Hackett said. "Our definition of 'good enough' is 'good enough to use
in a device.'"
And it worked. The team fabricated two molecular electronic devices, each with
a single-molecule layer of carbon chains. They used chains in different lengths
for each device. Both demonstrated the ability to resist electronic flow, with
the longer chains offering greater resistance, as expected.
The next step is to fabricate a CMOS-molecular hybrid circuit to show that
molecular electronic components can work alongside current microelectronic technologies.
The research is focused on developing components for high-performance computing
and it will still be quite a while before this technology is commercialized,
the researchers said.
William Jackson is the senior writer for Government Computer News (GCN.com).