Detection of individual CO2 molecules adsorption with suspended graphene in an electrical field

We report the sensing of carbon dioxide at the extreme resolution, I.e. the detection of an individual molecular adsorption event. We design a novel architecture of suspended graphene device, where comparable strain was introduced in graphene. With it, electrical field can be introduced to graphene surface by applying back-gate voltage to control the adsorption rates, while the collapsing of graphene onto substrate is effectively prevented. The step-like changes with a quantized value of ~ 62 Ω, that is about 0.56% of the background resistance, are measured in the graphene with the exposure to low concentration CO₂ molecules; the discrete response observed is a clear evidence to an individual adsorption event. The theoretical first principle calculation gives a value of resistance change of ~ 0.87% in graphene with one single molecule adsorption, which is in good agreement with our experiments.