Fabrication and characterization of NiPcTs organic semiconductors based surface type capacitive-resistive humidity sensors

This work describes the fabrication of surface type capacitive-resistive humidity sensors based on nickel(II) phthalocyanine-tetrasulfonic acid tetrasodium salt (NiPcTs) organic semiconductors as an active materials. The surface morphology of the NiPcTs thin film deposited on indium-tin-oxide (ITO) glass substrate at room temperatures is studied using field emission scanning electron micrographs (FE-SEM), shows that the film has high porosity and there is no particular crystal orientations in the NiPcTs films exist. A change in capacitance and electrical resistance of the fabricated devices are observed with the increase of relative humidity, for different applied frequencies. It is observed that the capacitance increases by 7.8 times with the increase in relative humidity (RH) from 60 to 95%, whereas the resistance is changed 22.8 times with the increase in relative humidity (RH) from 5 to 40%. The small values of hysteresis have been attained over a wide range of relative humidity (5-95%), indicating a good response/recovery of this device.