Engineers 'fine-tune' the sensitivity of a graphene chemical sensor
09 May 2013
Researchers at the University of Illinois at Chicago have discovered a technique for controlling the sensitivity of graphene chemical sensors.
The sensors, made of an insulating base coated with a graphene sheet are already so sensitive that they can detect an individual molecule of gas. But manipulating the chemical properties of the insulating layer, without altering the graphene layer, may yet improve their ability to detect the most minute concentrations of a variety of gases.
According to principal investigator, Professor Amin Salehi-Khojin, the finding will open up entirely new possibilities for modulation and control of the chemical sensitivity of these sensors, without compromising the intrinsic electrical and structural properties of graphene.
Composed of a single layer of carbon atoms, graphene has potential for use in hundreds of high-tech applications. Its 2D structure, exposing its entire volume, makes it attractive as a highly sensitive gas detector.
Salehi-Khojin’s team, and others, earlier found that graphene chemical sensors depended on a structural flaw around a carbon atom for their sensitivity. They set out to show that 'pristine' graphene sensors (made from flawless graphene) wouldn’t work. But when they tested these sensors, they found they were still sensitive to trace gas molecules.
“This was a very surprising result,” says Salehi-Khojin. The researchers tested the sensor layer by layer. They found that pristine graphene is insensitive, as they had predicted.
They next set about removing any flaws, or reactive sites called 'dangling bonds', from the insulating layer. When a pristine insulating layer was tested with pristine graphene, again there was no sensitivity.
However, when dangling bonds were added back onto the insulating layer, a response was observed. The inference is that graphene itself is insensitive unless it has defects – internal defects on the graphene surface or external defects on the substrate surface.
The researchers believe that controlling external defects in the supporting substrates will allow graphene chemFETs to be engineered that may be useful in a wide variety of applications.