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半导体学报 2011
Surface-type humidity sensor based on cellulose-PEPC for telemetry systems
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Abstract:
In this study, Au/Cellulose-PEPC/Au surface-type humidity sensors were fabricated by drop-casting cellulose and poly-N-epoxypropylcarbazole (PEPC) blend thin films. Blend of 2 wt.% of each cellulose and PEPC in benzol were used for the deposition of humidity sensing films. Blend films were deposited on glass substrates with preliminary deposited surface-type gold electrodes. Films of different thicknesses of cellulose and PEPC composite were deposited by drop-casting technique. A change in electrical resistance and capacitance of the fabricated devices were observed with the increase of relative humidity in the range of 0 95% RH. It was observed that the capacitances of the sensors increase, while their resistances decrease with increasing of the relative humidity. The sensors were connected to op-amp square wave oscillators. It was observed that with increase of relative humidity, the oscillator’s frequencies were also increased in the range of 4.2 12.0 kHz for 65 μm thick film sample and 4.1 9.0 kHz for 88 μm thick film sample and for 210 μm sample, the oscillator frequency changed in the range of 4.2 9.0 kHz. Effects of film thickness on the oscillator’s frequency with respect to humidity were also investigated. This polymer humidity sensor controlled oscillator can be used for short-range and long-range remote systems at environmental monitoring and assessment of the humidity level.
