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Journal of Sensors
Volume 2016, Article ID 4306154, 6 pages
Research Article

Unexpected Selectivity of UV Light Activated Metal-Oxide-Semiconductor Gas Sensors by Two Different Redox Processes

Department of Materials Science and Engineering, McMaster University, Hamilton, ON, Canada L8S 4L7

Received 27 November 2015; Revised 3 February 2016; Accepted 14 February 2016

Academic Editor: Sang Sub Kim

Copyright © 2016 Wenting Li and Gu Xu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The conflict between the two existing models was resolved, to provide a clear explanation for the unexpected “selectivity” found in UV light activated metal-oxide-semiconductor (MOS) gas sensors during the detection of reducing agents. A new model based on the dynamic equilibrium of adsorbed oxygen concentration was constructed by two types of responses: () when the MOS surface is adsorbed with oxygen, the conductance of the sensor increases upon injection of reducing agents (RA) (α-type) and () when the MOS surface is not covered by oxygen, the conductance decreases upon injection of RA (β-type). The proposed model was verified by the experiments of ZnO based MOS gas sensors, to reveal the origin of the unexpected “selectivity” found by the optimum intensity, where the current drop, due to the reaction between RA and MOS, which increases with UV power and levels with the reciprocal background current, which decreases with the UV power.