A polymer gate FET sensor array for detecting organic vapours

Here we describe a novel ChemFET sensor array that utilises carbon black composite polymers for the detection of organic vapours. Three vapour-sensitive composite polymers have been used as the gate materials of FET devices. A shift in the threshold voltage to toluene is observed with a linear dependence to concentration (Henry’s law) and a voltage sensitivity of up to 2.8 μV/ppm. The effects of humidity and temperature have also been examined and the magnitude of the response shows little dependence to humidity but an exponential fall with increasing temperature. We believe that this reduction in response is primarily due to a modification in the bulk solubility of the polymer. The shift in device threshold voltage may be caused by a change in the work function of the polymer composite, a swelling effect or a charge transfer effect. A generalised linear model is proposed here for the response of a ChemFET to an organic vapour at different humdities.