The team, which includes scientists from the Department of Physics and Astronomy and the Department of Electrical and Computer Engineering at Tufts University, used dielectrophoretic assembly to pattern RGO platelets in a field effect transistor geometry on SiO2/Si substrates. Transport measurements show that these chemical sensors display highly selective and reversible responses to the measured analytes, as well as fast response and recovery times on the order of tens of seconds.

Optimizing device design

Kelvin probe microscopy (KPM) measurements on RGO-based sensing devices allowed the researchers to obtain high-resolution maps of the surface potential and the local charge distribution both before and during the exposure of these sensors to different chemical species. KPM images were used to quantify the amount of charge transferred to the sensor during chemical doping and to spatially resolve the active sites of the sensor where the chemical gating process takes place. The data was also used to measure directly the contact resistance between the RGO platelets and the metallic electrodes.

The methods of measurement and analysis are general, and can be applied to the quantitative study of charge-transfer mechanisms in any two-dimensional chemical sensor.

Full details can be found in the journal Nanotechnology.