Is the Silicon Age over? Transistors without semiconductors

The team of researchers was able to develop boron nitride nanotube surfaces that were insulating materials and therefore could be particularly resistant to electric current. They started to conduct electric current selectively when they added gold nano dots

For decades now, electronic devices have become smaller and smaller; It is now possible, even routinely, to place millions of transistors on a single silicon chip.

However, transistors based on semiconductors can reach a final level of miniaturization. "At the rate at which existing technology is advancing today, in 20-10 years it will not be possible to miniaturize the chips anymore," says physicist Yoke Khin Yap from Michigan Technological University. "Also, semiconductors have another disadvantage - they cause considerable energy loss in the form of heat emission."

Scientists have performed many experiments with different materials and designs of transistors to solve this problem, and it has always been using semiconductors such as silicon. In 2007 researcher Yap wanted to try something else that might pave the way for a new era of electronic components. "My idea was to develop a transistor that includes a nanometer insulating material on which there are conductive nanometals," explained the researcher. "Basically, we could take a piece of plastic and sprinkle metal powder over it to get this device. However, we tried to create it on a nanometer level, so we chose the nanometer insulating material Boron Nitride Nanotubes (BNNTs) as the substrate."

The team of researchers was able to develop boron nitride nanotube surfaces that were insulating materials and therefore could be particularly resistant to electric current. In the next step, the team was able, with the help of a laser, to anchor gold quantum dots with a size of 3 nanometers along the upper side of the nanotubes, and this to create the material quantum dots-boron nitride nanotubes (QDs-BNNTs). These nanotubes are the perfect substrate for quantum dots due to their small, uniform and controllable dimensions. In the next step, the researchers connected electrodes to the ends of the new material at room temperature and at that moment an intriguing phenomenon occurred - electrons "jumped" very precisely from one gold spot to the second from one electrode to the second, a phenomenon known as "quantum tunneling".
"Imagine that the nanotubes are a river, with an electrode on each bank of the river. Now imagine that there are extremely small river stones across the river, between the two banks," says the researcher. "The electrons jump from one stone to another and in light of the fact that they are so tiny, only one electron can be found on each of them at the same moment. All the electrons go through the same path, so the device always remains stable."
In the end, the researchers were able to create a transistor without using semiconductor materials. When a sufficiently large voltage was applied to the material, it went into the state of a conductive material. When the current was reduced or stopped altogether, the material returned to its original state as an insulating material. And beyond that, there was no "leakage": none of the electrons that passed through the gold dots "leaked" into the self-insulating nanotubes, leaving the tunneling channel cold. Contrary to this, in silicon material there is a leakage of this type, a phenomenon that causes a significant loss of energy in electronic devices in the form of heat emission.

Other researchers have also succeeded in developing transistors that take advantage of the quantum tunneling phenomenon, says physicist John Jaszczak, who is the researcher who formulated the theoretical framework for Yap's applied research. However, these tunneling devices were only able to operate under conditions that were not adapted to the normal user in everyday life, and they only operated at extremely low temperatures, which they reached with the help of liquid helium. The secret to the new gold nanotube device is its sub-microscopic size: 1 micron long and 20 microns wide. "The size of the gold islands should be on the order of a few nanometers in order to control the flow of electrons at room temperature," explains the researcher. "If they are too large, the passage of many electrons at a time will be possible." In this case - smaller is indeed better: "Working with nanotubes and quantum dots advances you to the nanometric level that you want to use for the development of electronic devices. Theoretically, these tunneling channels can be minimized to almost zero dimensions when the distance between the electrodes is reduced to a micron-sized fraction," notes the lead researcher.

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