As the old saying goes, ‘small is beautiful’, electronic devices are getting smaller day by day. A small single chip contains millions of tiny semi-conductor based transistors. But according to physicist Yoke Khin Yap of Michigan Technological University, the current trend will come to a halt in a couple of decades. Moreover semiconductors waste lot of energy in the form of heat.
In order to overcome the drawbacks of semiconductor devices, scientists are trying to find alternative materials that can allow the devices getting even smaller.
Yap’s proposed an idea to build transistors using nanoscale insulators with nanoscale metals on top. This will result in a piece of plastic and a handful of metal powders spread on top for making the devices. He is trying to create it in nanoscale using nanoscale insulator, boron nitride nanotubes, or BNNTs for the substrate.
Yap’s team had found a way to create virtual carpets of BNNTs. As these are insulators they are highly resistant to electrical charge. The team used lasers to place quantum dots (QDs) of gold as small as three nanometers across on the tops of the BNNTs thereby forming QDs-BNNTs. BNNTs are the perfect substrates for quantum dots thanks to their small, controllable, and uniform diameters, as well as their insulating nature. BNNTs limit the size of the dots that can be deposited.
Yap’s team in collaboration with scientists at Oak Ridge National Laboratory (ORNL) fired up electrodes on both ends of the QDs-BNNTs at room temperature. Interestingly electrons jumped very precisely from gold dot to gold dot. This phenomenon is called quantum tunneling.
The electrons hopped between the tiny gold stepping stones and only one electron gets on the stone at a time. Each and every electron is passing in the same way so that the device is always in a stable state.
The transistor, produced by Yap’s team is a not a semiconductor based device. The transistor switches back and force between conducting state and insulator state depending on the voltage level. Sufficient voltage makes it switched to a conducting state and the low (or no) voltage reverts it to its natural state as an insulator.
Unlike semiconductor devices there is no leakage in these devices. That is, no electrons from the gold dots escaped into the insulating BNNTs thereby keeping the tunneling channel cool.
Yap’s transistors can work in room temperature. This is a major breakthrough as the other similar devices can only operate at liquid-helium temperatures.