Positive impedance and low hysteresis MOS type humidity sensors via SRCBD poly crystalline SnxOy thin films

Abstract

Resistivity-type humidity sensors have undergone extensive research as a result of the increasing demands in industry, agriculture, and daily life. Only a few carbon composites have been reported to exhibit positive humidity impedance, and the vast majority of humidity sensors currently in use are based on negative humidity impedance, in which electrical resistance increases as humidity levels increases. However, in this case, we only have fabricated positive impedance MOS type humidity sensors using SRCBD polycrystalline SnxOy thin films. By changing the composition of x and y due to air annealing, the resistance of SnxOy film sensors changes in response to relative humidity from a negative to a positive value. It was found that oxygen vacancy defects were the root cause of the positive humidity impedance. Positive humidity impedance sensors are more energy-efficient, simpler to miniaturize, and electrically safer than their negative counterparts as they operate at lower voltages, expanding the range of applications for humidity sensors. We also believe that by making vacancies in semiconducting materials, positive impedance humidity sensors can be made universally. A MOS device with low hysteresis was developed using SnxOy films that were air annealed at 450o C and can be used as a reliable humidity sensor in a variety of applications.