Paint-on semiconductor outperforms chips

Researchers at the University of Toronto have created a semiconductor device that claims to outperform conventional chips " and they made it by painting a liquid onto a piece of glass.

"Traditional ways of making computer chips, fibre-optic lasers and digital camera image sensors " the building blocks of the information age " are costly in time, money and energy," said Ted Sargent, Edward S Rogers Sr Department of Electrical and Computer Engineering and leader of the research group.

Conventional semiconductors have produced the personal computer, the internet and digital photography, but they rely on growing atomically-perfect crystals at 1000°C and above, he explained.

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 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 photodetectors were about 10 times more sensitive to infrared rays than the sensors that are currently used in military night-vision and biomedical imaging.

The development could be of importance to both research and industry, according to John Joannopoulos, a professor at MIT.

"The ability to realise 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," Joannopoulos said.

"The key to our success was controlled engineering at the nanometre-length scale: tailoring colloidal nanocrystal size and surfaces to achieve exceptional device performance," said lead author Gerasimos Konstantatos, a University of Toronto doctoral researcher.

"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."