Gate-bias controlled charge trapping as a mechanism for NO2 detection with field-effect transistors
article
Detection of nitrogen dioxide, NO2, is required to monitor the air-quality for human health and safety. Commercial sensors are typically chemiresistors, however field-effect transistors are being investigated. Although numerous investigations have been reported, the NO2 sensing mechanism is not clear. Here, the detection mechanism using ZnO field-effect transistors is investigated. The current gradually decreases upon NO2 exposure and application of a positive gate bias. The current decrease originates from the trapping of electrons, yielding a shift of the threshold voltage towards the applied gate bias. The shift is observed for extremely low NO2 concentrations down to 10 ppb and can phenomenologically be described by a stretched-exponential time relaxation. NO2 detection has been demonstrated with n-type, p-type, and ambipolar semiconductors. In all cases, the threshold voltage shifts due to gate bias induced electron trapping. The description of the NO2 detection with field-effect transistors is generic for all semiconductors and can be used to improve future NO2 sensors. The mechanism of NO2 detection is investigated using ZnO field-effect transistors. The transistor current gradually decreases upon NO2 exposure. The decrease originates from the trapping of electrons, which causes a shift of the threshold voltage towards the applied gate bias. The shift can be described by a stretched-exponential time relaxation and is observed for extremely low NO2 concentrations. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Topics
air quality sensorscharge trappingfield-effect transistorsNO2 sensorsZnOAmbipolar semiconductorChemiresistorsCommercial sensorsDetection mechanismElectron trappingExponential timeGate biasHuman healthNitrogen dioxidesNO sensorsP-typePositive gate biasSensing mechanismThreshold voltage shiftsZnOAir qualityBias voltageCharge trappingNitrogen oxidesSensorsThreshold voltageZinc oxideField effect transistors
TNO Identifier
461497
ISSN
1616301X
Source
Advanced Functional Materials, 21(1), pp. 100-107.
Pages
100-107
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