Annealing temperature and bias voltage dependency of humidity nanosensors based on electrospun KNbO3 nanofibers

Abstract

Humidity sensors based on nanofibers have been actively explored due to their unique structures comprising grains and grain boundaries. However, most of the resistance-type sensors lack linearity in sensing response and are operated at high voltages. In this report, resistance-type humidity nanosensors were fabricated from electrospun perovskite KNbO3 nanofibers and the effects of annealing temperature of nanofibers was investigated. A modified TGA setup was employed to test the absorption/desorption behaviour of the as-annealed nanofibers. KNbO3 nanofibers annealed at 550 °C displayed the highest sensitivity up to 104 for the humidity change from 15% to 90% RH. The I-V curves with respect to relative humidity (RH) measured at different biasing conditions revealed that disassociation of water molecules was dependent on the applied bias voltage thereby affecting the sensitivity. At higher RH environments, biasing the humidity nanosensor at higher voltage improved the linearity in the sensing response. Furthermore, the conductivity values of the as-fabricated humidity nanosensor were reproducible regardless of humidification and dehumidification process. The test outcomes from this study could offer better understanding on the design of high performance humidity sensors based on nanofibers.