UNCD thin films could improve the fabrication of biosensors

Scientists at Argonne National Laboratory’s Center for Nanoscale Materials have successfully carved ultra-nanocrystalline diamond (UNCD) thin films into nanowires.

The development is likely to increase the material’s functionality and provide potential improvements to the fabrication of biosensors.

UNCD thin films are a special form of diamond invented at ANL and are a subject of interest because of the material’s ability to alter its electrical properties when the chemical bonding between grain boundaries is modified.

‘It’s a highly attractive carbon-based material with a range of applications in communications, medicine and defence,’ said team leader Anirudha Sumant, a materials scientist at ANL.

A primary motive behind the team’s studies, he said in a statement, is to understand the electrical transport properties of UNCD when it’s fabricated into a nanowire geometry. Similarly, they wanted to see how these properties can be altered by changing chemical bonding at the grain boundary and by taking advantage of increased surface-to-volume ratio simultaneously.

‘We’ve demonstrated a pathway to fabricate UNCD nanowires, with widths as small as 30 nanometres at a thickness of 40 nanometres, by using a top-down fabrication approach that combines electron-beam lithography and a reactive ion-etching process,’ said Sumant.

Among the electrical properties of the UNCD nanowires, the researchers also discovered a resistance that is extremely sensitive to the adsorption of gas molecules at the grain boundaries. This discovery is said to open up possibilities for the fabrication of advanced nanoscale sensors for specific use.

Sumant added that the main advantage of UNCD over other materials is that it provides stable functionalisation, which could be useful for fabricating a new breed of sensors.

UNCD nanowires are initially expected to find applications in the biosensor area, or in pressure or gas sensors, which could be used by the micro-electromechanical systems (MEMS) and semiconductor industries.