Substrate Effects on the Transient Chemiresistive Gas Sensing Performance of Monolayer Graphene

Chemiresistive oxygen sensing experiments on graphene have shown a wide range of sheet conductivities, with mean values that depend on the sensor substrate, and an order of magnitude variation between reported values for experiments conducted with the same substrate. Recent research by the authors has performed a new series of experiments investigating substrate effects on chemiresistive oxygen sensing with monolayer graphene. The testing included four different substrates, ranging from the most commonly used (silicon dioxide over silicon) to one almost never used (hexagonal boron nitride (hBN) over silicon). The experiments employed eddy current testing, eliminating variations in contact resistance included in the published database, and a single graphene supplier, eliminating variations in graphene quality included in the published database. The results show a strong dependence of the measured sheet conductance on the graphene substrate, including (in the most pronounced case) a sign reversal of the change in conductance induced by oxygen adsorption. This observed substrate dependence may be exploited, by introducing sensor arrays composed of monolayer graphene deposited on different types of substrates, to add selectivity to chemiresistive gas sensors.