Wednesday, 31 July 2013

Guided growth of nanowires leads to self-integrated circuits

Guided growth of nanowires leads
to self-integrated circuits
This is a SEM image of a logic circuit
based on 14 nanowires. Credit:
Weizmann Institute of Science
Researchers working with tiny
components in nanoelectronics face a
challenge similar to that of parents
of small children: teaching them to
manage on their own. The nano-
components are so small that
arranging them with external tools is
impossible. The only solution is to
create conditions in which they can
be "trusted" to assemble themselves.
Much effort has gone into facilitating
the self-assembly of semiconductors,
the basic building blocks of
electronics, but until recently,
success has been limited. Scientists
had developed methods for growing
semiconductor nanowires vertically
on a surface, but the resultant
structures were short and
disorganized. After growing, such
nanowires need to be "harvested"
and aligned horizontally; since such
placement is random, scientists need
to determine their location and only
then integrate them into electric
circuits.
A team led by Prof. Ernesto
Joselevich of the Weizmann
Institute's Materials and Interfaces
Department has managed to
overcome these limitations. For the
first time, the scientists have created
self-integrating nanowires whose
position, length and direction can be
fully controlled.
The achievement, reported today in
the Proceedings of the National
Academy of Sciences ( PNAS), USA,
was based on a method developed
by Joselevich two years ago for
growing nanowires horizontally in an
orderly manner. In the present study
—conducted by Joselevich with Dr.
Mark Schvartzman and David Tsivion
of his lab, and Olga Raslin and Dr.
Diana Mahalu of the Physics of
Condensed Matter Department—the
scientists went further, creating self-
integrated electronic circuits from the
nanowires.
First, the scientists prepared a
surface with tiny, atom-sized grooves
and then added to the middle of the
grooves catalyst particles that served
as nuclei for the growth of
nanowires. This setup defined the
position, length and direction of the
nanowires. They then succeeded in
creating a transistor from each
nanowire on the surface, producing
hundreds of such transistors
simultaneously. The nanowires were
also used to create a more complex
electronic component—a functioning
logic circuit called an Address
Decoder, an essential constituent of
computers. These ideas and findings
have earned Joselevich a prestigious
European Research Council Advanced
Grant.
"Our method makes it possible, for
the first time, to determine the
arrangement of the nanowires in
advance to suit the desired electronic
circuit," Joselevich explains. The
ability to efficiently produce circuits
from self-integrating semiconductors
opens the door to a variety of
technological applications, including
the development of improved LED
devices, lasers and solar cells.
Provided by Weizmann Institute of
Science

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