Abstract
The present study highlights the interdependence of ambient humidity levels on the electrical parameters of organic-inorganic hybrid composite based humidity sensor at varied AC frequencies of input signal. Starting from the bottom, the layer stack of the fabricated humidity sensor was 200-nm silver (Ag) thin film and 4 μm spun-coated PEPC+NiPC+Cu2O active layer. Silver thin films were deposited by thermal evaporator on well cleaned microscopic glass slides, which served as a substrate. Conventional optical lithography procedure was adapted to define pairs of silver-silver surface electrodes with two sorts of configurations, i.e., interdigitated and rectangular. Humidity-sensitive layers of organic-inorganic composite were then spun-cast upon the channel between the silver electrodes. The changes in relative humidity levels induced variation in capacitance and impedance of the sensors. These variations in electrical parameters of sensors were also found to be highly dependent upon frequency of input AC signal. Our findings reveal that the organic-inorganic composite shows higher humidity sensitivity at smaller orders of frequency. This finding is in accordance with the established fact that organic semiconductors-based devices are not applicable for high frequency applications due to their lower charge carrier mobility values. Two distinct geometries of semiconducting medium between the silver electrodes were investigated to optimize the sensing parameters of the humidity sensor. Furthermore, the effect of temperature change on the resistance of organic composite has also been studied.
Highlights
The need for sensors in the environmental monitoring and medical diagnostics domain is ever increasing [1,2,3,4]
Because it is insoluble in water, we considered the organic-inorganic hybrid composite (Cu2 O-poly-N-epoxy propyl carbazole (PEPC)-NiPC) an ideal candidate for humidity monitoring
The interdependence of the humidity levels and electrical parameters of the sensor was studied in a wide frequency range (300 Hz–100 KHz)
Summary
The need for sensors in the environmental monitoring and medical diagnostics domain is ever increasing [1,2,3,4]. Despite the advantages, viz., low power consumption and linearity in response, mostly humidity sensors are based on capacitive type sensing. Their working principle is based upon the dielectric permittivity variation resulting from absorption of water vapors by a sensing layer. It is well known that hydrophobic materials are generally used for fabrication of humidity sensors, otherwise the sensing layer may peel off due to dissolution in water at higher humidity levels. Because it is insoluble in water, we considered the organic-inorganic hybrid composite (Cu2 O-PEPC-NiPC) an ideal candidate for humidity monitoring. We have compared the effect of electrode configuration for the optimization of the sensor’s response as well
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