Effect of humidity on electronic properties of CVD graphene
The two-dimensional nature of graphene makes it sensitive to environmental doping. With water vapour being a significant component of the ambient air, graphene-based devices designed to operate in ambient air (e.g. sensors) will be significantly affected, as their electronic properties will change with humidity. For the successful commercialisation of graphene-based devices, the complete understanding of the water-graphene interactions is necessary.
In this work, we employ local Kelvin probe force microscopy (KPFM) and global transport measurements in the van der Pauw geometry to observe the effects of water on the surface potential and carrier density of chemical vapour deposition (CVD) grown graphene of different thicknesses transferred on SiO2. The study of the local surface potential is directly correlated to the electronic properties of graphene, such as work function and environmental doping. We probe the local electronic properties of 1-2 layer graphene in a series of measurements in controlled environments, starting from ambient, to vacuum, pure nitrogen and 20-80% relative humidity (RH), by simultaneously measuring the surface potential and carrier concentration.
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