Paint-On Semiconductor Outperforms Chips
7/25/2006 Toronto -- Researchers at the University of Toronto have created a
semiconductor device that outperforms today’s conventional chips — and they made
it simply by painting a liquid onto a piece of glass.
The finding, which represents the first time a so-called “wet” semiconductor
device has bested traditional, more costly grown-crystal semiconductor devices,
is reported in the July 13 issue of the journal Nature.
“Traditional ways of making computer chips, fibre-optic lasers, digital
camera image sensors – the building blocks of the information age – are costly
in time, money, and energy,” says Professor Ted Sargent of the Edward S. Rogers
Sr. Department of Electrical and Computer Engineering and leader of the research
group. Conventional semiconductors have produced spectacular results — the
personal computer, the Internet, digital photography — but they rely on growing
atomically-perfect crystals at 1,000 degrees Celsius and above, he explains.
The Toronto team instead cooked up semiconductor particles in a flask
containing extra-pure oleic acid, the main ingredient in olive oil. The
particles are just a few nanometres (one billionth of a metre) across. The team
then placed a drop of solution on a glass slide patterned with gold electrodes
and forced the drop to spread out into a smooth, continuous semiconductor film
using a process called spin-coating. They then gave their film a two-hour bath
in methanol. Once the solvent evaporated, it left an 800 nanometre-thick layer
of the light-sensitive nanoparticles.
At room temperature, the paint-on photo-detectors were about ten times more
sensitive to infrared rays than the sensors that are currently used in military
night-vision and biomedical imaging. “These are exquisitely sensitive detectors
of light,” says Sargent, who holds a Canada Research Chair in Nanotechnology.
“It’s now clear that solution-processed electronics can combine outstanding
performance with low cost.” The U of T development could be of critical
importance to both research and industry, according to John D. Joannopoulos, a
professor at MIT. “The ability to realize low-cost, paintable, high-performance
designer semiconductors for use as short-wavelength infrared detectors and
emitters is of enormous value for a wide range of communications, imaging and
monitoring applications,” says Joannopoulos, the Francis Wright Davis Professor
of Physics and director of the Institute for Soldier Nanotechnologies at the
Massachusetts Institute of Technology.
“The key to our success was controlled engineering at the nanometre
lengthscale: tailoring colloidal nanocrystal size and surfaces to achieve
exceptional device performance,” says lead author Gerasimos Konstantatos, a
doctoral researcher at UofT. “With this finding, we now know that simple,
convenient, low-cost wet chemistry can produce devices with performance that is
superior compared to that of conventional grown-crystal devices.”
The research was supported by the Natural Sciences and Engineering Research
Council (NSERC) of Canada through its Idea to Innovation (I2I) Program, the
Canada Foundation for Innovation; the Province of Ontario through the Ontario
Centres of Excellence and the Canada Research Chairs program.
SOURCE: University of Toronto
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