Epitaxially grown graphene based gas sensors for ultra sensitive NO2 detection

Epitaxially grown single layer and multi layer graphene on SiC devices were fabricated and compared for response towards NO2. Due to electron donation from SiC, single layer graphene is n-type with a very low carrier concentration. The choice of substrate is demonstrated to enable tailoring of the electronic properties of graphene, with a SiC substrate realising simple resistive devices tuned for extremely sensitive NO2 detection. The gas exposed uppermost layer of the multi layer device is screened from the SiC by the intermediate layers leading to a p-type nature with a higher concentration of charge carriers and therefore, a lower gas response. The single layer graphene device is thought to undergo an n–p transition upon exposure to increasing concentrations of NO2 indicated by a change in response direction. This transition is likely to be due to the transfer of electrons to NO2 making holes the majority carriers.