Enhancing gas sensing properties of graphene by using a nanoporous substrate
Substrate engineering is shown to be a viable approach for improving the use of graphene thin films for gas sensor applications. The performance of two terminal devices fabricated on smooth SiO2 and nanoporous anodized aluminum oxide (AAO) substrates are compared. Raman studies indicated that both types of samples exhibit similarly low point defect densities, but the mobility values of the SiO2 supported films were found to be three times larger than those on porous AAO substrates. However, the AAO supported graphene devices exhibit a 3 fold enhanced sensitivity to both NO2 and NH3 gases when compared to the devices supported on SiO2. We attribute this sensitivity enhancement to the inhomogeneous electrostatic potential landscape that results from the porous nature of the AAO substrate, as well as extended defects made of wrinkles or folds originated from AAO. This substrate design strategy could be extended to other semiconductor based sensor devices.