Graphene Films and Ribbons for Sensing of O₂, and 100 ppm of CO and NO₂ in Practical Conditions

Graphene films and ribbons were grown on Ni-coated Si substrates using the microwave plasma enhanced chemical vapor deposition method. We report the structure, morphology, and quality of graphene films and ribbons. The semiconducting nature of the CVD-grown graphene was observed by studying resistance−temperature variation in the range 25 to 200 °C, using the four-point probe method. Graphene exhibited an increase of resistance upon exposure of CO and a decrease in resistance upon pure O 2 and NO 2 exposures. It was observed that graphene films show sensor signal ∼3 and 35 for 100 ppm of CO and 100 ppm of NO 2 whereas the graphene ribbons show the sensor signal values of 1.5 and 18 for 100 ppm of CO and 100 ppm of NO 2 . The gas sensor mechanism was observed to be mainly dependent on the charge carrier transfer on conducting graphene surfaces caused by the adsorption of gases.