The
narrowest conducting wires in silicon ever made—just four atoms wide
and one atom tall—have been shown to have the same electrical current
carrying capability of copper, according to a new study published today
in the journal Science.
Despite
their astonishingly tiny diameter—10,000 times thinner than a human
hair—these wires have exceptionally good electrical properties, raising
hopes they will serve to connect atomic-scale components in the quantum
computers of tomorrow.
“Interconnecting
wiring of this scale will be vital for the development of future
atomic-scale electronic circuits,” says the lead author of the study,
Bent Weber, a PhD student in the ARC Centre of Excellence for Quantum
Computation and Communication Technology at the University of New South
Wales, in Sydney, Australia.
The
wires were made by precisely placing chains of phosphorus atoms within a
silicon crystal, according to the study, which includes researchers
from the University of Melbourne and Purdue University in the US.
The
researchers discovered that the electrical resistivity of their wires—a measure of the ease with which electrical current can flow—does not
depend on the wire width. Their behaviour is described by Ohm’s law,
which is a fundamental law of physics taught to every high school
student.
“It
is extraordinary to show that such a basic law still holds even when
constructing a wire from the fundamental building blocks of
nature—atoms,” says Weber.
The
discovery demonstrates that electrical interconnects in silicon can
shrink to atomic dimensions without loss of functionality, says the
Centre’s Director and leader of the research, Professor Michelle
Simmons.
“Driven
by the semiconductor industry, computer chip components continuously
shrink in size allowing ever smaller and more powerful computers,”
Simmons says.
“Over
the past 50 years this paradigm has established the microelectronics
industry as one of the key drivers for global economic growth. A major
focus of the Centre of Excellence at UNSW is to push this technology to
the next level to develop a silicon-based quantum computer, where single
atoms serve as the individual units of computation,” she says.
“It
will come down to the wire. We are on the threshold of making
transistors out of individual atoms. But to build a practical quantum
computer we have recognised that the interconnecting wiring and
circuitry also needs to shrink to the atomic scale.”
Creating
such tiny components has been made possible using a technique called
scanning tunnelling microscopy. “This technique not only allows us to
image individual atoms but also to manipulate them and place them in
position,” says Weber.
