Sezawa wave acoustic humidity sensor based on graphene oxide sensitive film with enhanced sensitivity

The measurement of humidity is very important for air control in ambient, industry, cars, houses, closed apartments, museums, atomic power stations, etc. In the present work the theoretical analysis of the surface acoustic wave propagation in “graphen oxide (GO) film/ZnO film/Si substrate” layered structure has been performed. The change of GO film conductivity due to humidity has been taken into account during the calculations. Based on the obtained results an improved microwave acoustic humidity sensor has been developed. The sensor has enhanced sensitivity of about 91 kHz/% and linear response vs relative humidity in the range 20-98%RH. It is based on the mode belonging to Sezawa wave family that is shown to be more sensitive towards electric conductivity variations in GO film produced by adsorbed water molecules than the Rayleigh counterpart.