Sunday, June 23, 2013
Now, transistors without semiconductors
A team of scientists have figured
out how to make virtual carpets of boron nitride nanotubes (BNNT),
which happen to be insulators and thus highly resistant to electrical
charge.
Using lasers, researchers placed quantum dots (QDs) of gold as small
as three nanometers across on the tops of the BNNTs, forming QDs-BNNTs.
BNNTs are the perfect substrates for these quantum dots due to their
small, controllable, and uniform diameters, as well as their insulating
nature. BNNTs confine the size of the dots that can be deposited.In collaboration with scientists at Oak Ridge National Laboratory (ORNL), they fired up electrodes on both ends of the QDs-BNNTs at room temperature, and something interesting happened. Electrons jumped very precisely from gold dot to gold dot, a phenomenon known as quantum tunneling.
Physicist Yoke Khin Yap of Michigan Technological University said the electrons hopped between the gold stepping stones and the stones are so small, that you can only get one electron on the stone at a time. Every electron is passing the same way, so the device is always stable.
Yap's team had made a transistor without a semiconductor. When sufficient voltage was applied, it switched to a conducting state. When the voltage was low or turned off, it reverted to its natural state as an insulator.
Furthermore, there was no
"leakage": no electrons from the gold dots escaped into the insulating
BNNTs, thus keeping the tunneling channel cool. In contrast, silicon is
subject to leakage, which wastes energy in electronic devices and
generates a lot of heat.
The secret to Yap's gold-and-nanotube device is its submicroscopic size: one micron long and about 20 nanometers wide.
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