However, as anticipated, such semiconductor transistors can only get so small. As stated by the physicist Yoke Khin Yap of Michigan Technological University - "at the rate the current technology is progressing, in 10 or 20 years, they won't be able to get any smaller," - "also, semiconductors have another disadvantage: they waste a lot of energy in the form of heat." Knowing of such issues - scientists have continued to experiment with different materials and designs for transistors to address such hindrances, but always employing semiconductors like Si. However, back in 2007 - Yap aspired to try something different, which might open the door to a new age/range of electronics.
In essence the principle of the idea was to fabricate a transistor by employing a nano-scale insulator with nano-scale metals on top. Yap stated "In principle, you could get a piece of plastic and spread a handful of metal powders on top to make the devices, if you do it right. But we were trying to create it in nano-scale, so we chose a nano-scale insulator, boron nitride nanotubes, or BNNTs for the substrate."
Yap's group had understood how to make virtual carpets with BNNTs. BNNTs are known to typically act like insulators and so highly resistant to electrical charge. Employing lasers - the team then meticulously placed quantum dots (QD) of Gold (Au) across on the tops of the BNNTs - effectively forming QDs-BNNTs. BNNTs are seen as perfect substrates for QDs, due to their small, controllable, uniform diameters as well as their insulating nature. BNNTs confine the size of the dots that can be deposited.
In collaboration with researchers at Oak Ridge National Laboratory (ORNL) - they fired electrodes on both ends of the QDs-BNNTs at room temperature (RT), whereby something interesting occurred. Effectively electrons jumped very precisely from Au dot to Au dot - a phenomenon known as quantum tunneling. As Yap explains - "imagine that the nanotubes are a river, with an electrode on each bank. Now imagine some very tiny stepping stones across the river," whereby "the electrons hopped between the Gold stepping stones. The stones are so small, 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."
The innovative design by Yap's team had consisted of a transistor without a semiconductor, which when sufficient voltage was applied - it would switch to a conductive state. Conversely when the voltage was low or turned-off, then the non-semiconductor transistor reverted to its natural state as an insulator. In addition, there is no "leakage", such as no electrons from the Au dots escaped into the insulating BNNTs, thus, keeping the tunneling channel cool. In direct comparison - Si is subject to leakage, which wastes energy in electronic devices and generates a lot of heat.
In summary, the key to Yap's transistor design is the Au-and-nanotube sub-microscopic size - one micron long and 20 nm wide. As articulately postulated by a Michigan Tech physicist - John Jaszczak (Yap's theoretical co-researcher) - "the gold islands have to be on the order of nanometers across to control the electrons at room temperature," and "if they are too big, too many electrons can flow". In this scenario - smaller is very much better - "working with nanotubes and quantum dots gets you to the scale you want for electronic devices." Original article available here
As with other similar kind of nano-articles - DCN Corp finds the above research extremely interesting and would like to understand if the above non-semiconductor transistor design can be improved by DCN Corp's means of homogeneous nano-fabrication? If so, and you or your colleagues are interested in making the above a reality - please ensure to contact the company as soon as practicably possible.