Investigation of the relative humidity-sensing performance of capacitive and resistive type sensor based on metalloporphyrin dielectric layer
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Date
2020
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UMT, Lahore
Abstract
A quest for a suitable method to fabricate thin films based humidity sensor with superior sensitivity in their electric response, calls for a selection of an appropriate material and effective fabrication technique. Organic semiconductors/polymers have particularly significant potential for relative humidity sensing applications as they offer controlled pore size, low-cost & vast variety of fabrication procedures and inherent advantage of mechanical flexibility. In this article, application of organic semiconductor metalloporphyrin (TDTBPPNi) to fabricate highly sensitive humidity sensors by using a novel eco-benign microwave-assisted synthetic procedure has investigated. Metalloporphyrin (TDTBPPNi) has synthesized and deposited through facile drop-casting technique on the gap (40 μm) between a set of planar aluminum (Al) electrodes to fabricate a planar coherent resistive and capacitive type humidity sensor (Al/TDTBPPNi/Al). The structural and morphological characterization of relative humidity sensing active layer has examined by XRD and AFM, which indicates amorphous structure and rough globular surface morphology of the active surface thin film. The relative humidity sensing capacitive and resistive characteristics of the humidity sensor have been explored by exposing it to various wide range relative humidity (%RH) levels (39 - 85 %RH). The fabricated sensor under biasing condition of 1V of applied bias (Vrms) and 200 Hz AC test frequency, exhibits significantly higher sensitivity of ~ 102.61 pF/%RH and -333.07 kΩ/%RH in capacitive and resistive mode of operation. The average response time and recovery time of this resistive sensor have evaluated to be ~ 35 s and ~57 s, respectively. The reasons of this achieved sensitivity and response level has discussed.