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.
"But when dangling bonds were added back onto the insulating layer, we observed a response," said Bijandra Kumar, a post-doctoral research associate at UIC and first author of the Nano Letter study.
"We could now say that graphene itself is insensitive unless it has defects--internal defects on the graphene surface, or external defects on the substrate surface," said UIC graduate student Poya Yasaei.
The finding opens up a new "design space," Salehi-Khojin said. Controlling external defects in the supporting substrates will allow graphene chemFETs to be engineered that may be useful in a wide variety of applications.
|Contact: Jeanne Galatzer-Levy|
University of Illinois at Chicago