Tiny devices could combat overheating in electronics

A team of scientists from the Tyndall National Institute at University College Cork (UCC) and the National University of Singapore have designed and fabricated ultra-small devices for energy-efficient electronics.

It is claimed that by finding out how molecules behave in these devices, a 10-fold increase in switching efficiency was obtained by changing a single carbon atom.

These devices could provide new ways to combat overheating in mobile phones and laptops, and could also assist with the electrical stimulation of tissue repair for wound healing.

Dr Damien Thompson of the Tyndall National Institute at UCC and a team of researchers at the National University of Singapore led by Prof Chris Nijhuis designed and created the devices, which are based on molecules acting as electrical valves, or diode rectifiers.

In a statement, Thompson said: ‘These molecules are very useful because they allow current to flow through them when switched on and block current flow when switched off. The results of the study show that simply adding one extra carbon is sufficient to improve the device performance by more than a factor of 10.’

Thompson’s atom-level computer simulations showed how molecules with an odd number of carbon atoms stand straighter than molecules with an even number of carbon atoms, allowing them to pack together more closely.

Tightly packed assemblies of these molecules were formed on metal electrode surfaces by the Nijhuis group in Singapore and were found to be free of defects.

The device can be switched on and off on the basis of the charge and shape of the molecules, just like in the biological nano-machines that regulate photosynthesis, cell division and tissue growth.

Tyndall Electronic Theory Group leader Prof Jim Greer said: ‘Modern electronic devices such as telephones and tablets in manufacture today rely on tiny switches approaching molecular sizes. This provides new challenges for electronics but opens up exciting opportunities for blending molecular properties to be used to advantage. Dr Thompson’s work is an exciting new avenue to exploit molecular design to achieve new ways to perform information processing.’

A key enabling feature for nanoscale electronics will be the ability to use molecules as rectifiers and switches.

By demonstrating the rational design of molecules that rectify current with a large and highly reproducible on/off ratio, the study provides a key advance towards the creation of technologically viable ultra-small device components.

The study was funded on the Irish side by a Science Foundation Ireland Starting Investigator award to Thompson. The computer simulations were performed on Science Foundation Ireland-supported computing clusters at Tyndall and at the Irish Centre for High End Computing.

The combined experiments and simulations show that minute improvements in molecule orientation and packing trigger changes in van der Waals forces that are sufficiently large to improve the performance of electronic devices.

The creation of molecular devices with highly controllable electrical properties will appear in the February issue of Nature Nanotechnology.