BUFFALO, N.Y. -- In the quest to pack ever-smaller electronic
devices more densely with integrated circuits, nanotechnology
researchers keep running up against some unpleasant truths: higher
current density induces electromigration and thermomigration,
phenomena that damage metal conductors and produce heat, which
leads to premature failure of devices.
But University at Buffalo researchers who study electronics
packaging recently made a pleasant discovery: that's not the case
with Single-Walled Carbon Nanotubes (SWCNTs).
"Years ago, everyone thought that the problem of cooling for
electronics could be solved," said Cemal Basaran, Ph.D., professor
in the UB Department of Civil, Structural and Environmental
Engineering and director of the Electronics Packaging Lab in UB's
School of Engineering and Applied Sciences. "Now we know that's not
true. Electronics based on metals have hit a wall. We are done with
Single Walled Carbon Nanotubes are extremely thin, hollow
cylinders, measuring no thicker than a single atom. Thousands of
times stronger than metals, they are expected to one day replace
metals in millions of electronic applications.
Basaran and his doctoral student Tarek Ragab have spent the past
four years performing quantum mechanics calculations, which prove
that in carbon nanotubes, higher current density does not lead to
electromigration and thermomigration; it also produces just one
percent of the heat produced by traditional metals, such as
Basaran will present the findings in November when he delivers a
keynote lecture at the American Society of Mechanical Engineers
(ASME) International Mechanical Engineering Congress and Exposition
The findings demonstrate yet another tantalizing property of
CNTs, he said.
"It has been assumed that for carbon nanotubes, the electrical
heating process would be governed by Joules law, where resistance
in a circuit converts electric energy into heat," said Basaran. "We
are the first to show mathematically, from a quantum mechanics
point of view, that carbon nanotubes do not follow Joules law."
According to Basaran, this essential difference between metals
and carbon nanotubes lies in the way they conduct electricity.
"Even though carbon nanotubes are conductive, they do not have
metallic bonds," he said. "As a result, they do not conduct
electricity the way that traditional metals do."
In conventional metals, he explained, conduction causes a
scattering of electrons within the lattice of the material so that,
when electrons move during conduction, they bump into atoms. This
creates friction and generates heat, the same way a household iron
"On the other hand, in carbon nanotubes, electric conduction
happens in a very different, one-dimensional 'ballistic' way," he
said. "The electrons are fired straight through the material, so
that the electrons have very little interference with the
He drew an analogy, using the difference between a conventional
railroad train and a magnetically levitated train.
"In the conventional train, you have friction between the wheels
and the track," said Basaran. "Through the generation of heat, that
friction causes a loss of energy. But with a magnetically levitated
train, the wheels and track are not in direct contact. Without that
friction, they can travel much faster."
The minimal amount of friction gives carbon nanotubes a
tremendous advantage over conventional metals, said Basaran. The
unique properties of carbon nanotubes will allow engineers to
realize a host of smaller, faster and more powerful new devices
that right now cannot exist because of the limitations of
"When an electric car finally is manufactured, its batteries
probably will be based on carbon nanotubes," said Basaran. "You
can't use traditional metals in the engines because they run so
Much of Basaran's $1 million-plus funding at UB comes from
sources like the U.S. Navy, which is interested in sophisticated
electronics systems that could operate under very demanding
conditions, such as the electric ship the Navy is building.
Basaran's unique perspective comes from decades of research,
which has fundamentally changed what is known about the high
current density performance properties of metals and their
He also sounded a cautionary note, pointing out that current
research and development expenditures on carbon nanotubes in the
U.S. electronics industry are very small when compared to those of
our Asian competitors.
"If the industry continues this way, when carbon nanotube-based
electronics become a reality, U.S. electronics manufacturers may be
in a position similar to U.S. car manufacturers today, because they
have failed to keep up with advances in engineering," he said.
Basaran and his colleagues in the Electronics Packaging Lab
actively participate in the UB 2020 strategic strength in
Integrated Nanostructured Systems, which brings together physicists
and engineers to further enhance and understand nanotechnologies
like carbon nanotubes.
The University at Buffalo is a premier research-intensive public
university, a flagship institution in the State University of New
York system and its largest and most comprehensive campus. UB's
more than 28,000 students pursue their academic interests through
more than 300 undergraduate, graduate and professional degree
programs. Founded in 1846, the University at Buffalo is a member of
the Association of American Universities.