Researchers find new way to control electrons

The breakthrough could improve the performance of electrical devices. Among the research team are (from left) Prof Castro Neto, Dr Li Linjun, Dr Eoin O'Farrell and Prof Barbaros Ozyilmaz.
The breakthrough could improve the performance of electrical devices. Among the research team are (from left) Prof Castro Neto, Dr Li Linjun, Dr Eoin O'Farrell and Prof Barbaros Ozyilmaz.PHOTO: NATIONAL UNIVERSITY OF SINGAPORE

Scientists from the National University of Singapore (NUS) have found a new way to control how electrons move in a breakthrough that could improve the performance of electrical devices.

Electrons are sub-atomic particles found in all matter that carry a negative charge. The flow of electrons is what gives rise to electricity.

However, directing their movement is not easy.

"Not only are electrons small and fast, they naturally repel each other due to their electric charge," said Professor Antonio Castro Neto, from the Centre for Advanced 2D Materials of the NUS Faculty of Science. "They obey the strange laws of quantum physics, making it difficult to control their motion directly."

To control electron behaviour, many semiconductor materials require chemical doping, where small amounts of a foreign material are embedded in the material to either release or absorb electrons.

This poses a problem for research in this field, since the doping irreversibly changes the chemical properties of the material being studied.

But the NUS team, led by Prof Castro Neto, discovered a new way to control electrons that is reversible and less invasive than doping the semiconductor material.

After two years of research, the team has demonstrated that it can be done using atomically thin semiconductor materials that are 100,000 times thinner than a strand of human hair, and then applying external electric and magnetic fields to it.

Using a thin semiconductor material - in this case, titanium diselenide coated with boron-nitride - is the key to the new find, noted Prof Castro Neto.

Because it is so thin, the electrons are confined to a two-dimensional layer instead of a three-dimensional structure found in other types of semiconductors. This made all the electrons uniformly susceptible to the external force fields (electrons are affected by magnetic and electrical currents because of their negative charge).

The researchers found that they were able to replicate the effects of chemical doping using this technique accurately and reversibly.

Their findings were published in the prestigious scientific journal Nature yesterday.

The next step, Prof Castro Neto said, is to develop high-temperature, two-dimensional superconducting materials. "Current materials require an extremely cold temperature of -270 deg C to function, ruling out exciting applications such as lossless electrical lines, levitating trains and MRI machines," he noted.

A version of this article appeared in the print edition of The Straits Times on December 24, 2015, with the headline 'Researchers find new way to control electrons'. Print Edition | Subscribe