Analytical assessment of carbon allotropes for gas sensor applications

Abstract

Feasibility of a gas sensor with NH3 as a prototype using carbon allotropes (graphene and CNT) is demonstrated, with graphene displaying superior sensitivity and conductance. Such devices are expected to be considerably smaller and faster than the ones used in the present technology. Salient features of current–voltage characteristics of charge transfer as NH3 reacts with carbon atoms and transfer charge is demonstrated. A mathematical model is proposed for change in conductance of the CNT/graphene channel resulting from the chemical reaction between the gas and channel surface molecules. An analytical understanding of the FET-based gas detection mechanism and the corresponding current–voltage (I–V) characteristics is acquired. The CNT model shows a satisfactory agreement with the experimental data on nanotube-based NH3 gas detection. The results of the graphene-based gas sensor model are compared to those from the CNT model. It is shown that for similar ambient conditions, the graphene gas sensor exhibits superior conduction as compared to its CNT counterpart due to higher exposed surface of graphene.