Realization of self-bias humidity sensor, based on ZnO nanosheets

ZnO nanowires, among other peizoelectric nanostructures, have been frequently applied to realize nanogenerators (NGs). However, it has been recently shown that ZnO nanosheets have higher mechanical strength than the nanowires, which entitles them as another candidate in this field of application. In this paper, we report fabrication of a piezoelectric NG based on ZnO nanosheets and then propose the fabricated NG as an efficient self-bias humidity sensor. ZnO nanosheets are grown by hydrothermal method, on Al substrate. The measured output power of NG is about 372 nW/g.cm2. It is believed that exposing the NG to gas molecules, changes the density of free carriers in the nanosheets, which alters the output power of the NG. Our study demonstrates that the output power increases to about 1180 nW/g.cm2, when the NG is exposed to humidity with a Relative humidity (RH) about 28%. Hence, a sensitivity (S=ΔP/P0) of about 5×10-3is achieved at RH of 28%, for the fabricated self-bias humidity sensor.