Kinetic factors in the response of organometallic semiconductor gas sensors

Abstract The influences of thermal-treatment and gas-exposure history on the kinetics of the electrical conductivity changes occurring in sublimed films of lead phthalocyanine, chloroaluminium phthalocyanine, fluoroaluminium phthalocyanine and tetraazadibenzo[14]-annulene and its copper complex on exposure to sub-parts per million (ppm) concentrations of nitrogen dioxide (NO 2 ) in air have been studied. Freshly sublimed films are sensitized to nitrogen dioxide on heating in air. Thermally-induced structural changes and the creation of traces of strongly-bound nitrogen dioxide species that exercise a catalytic role in facilitating displacement of oxygen from surface sites are shown to be responsible for these changes. Their significance in determining the kinetics of the response of organic semiconductor gas sensors is discussed, together with implications for the optimization of the operating modes of such sensors.

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