ZnO thin film sensor

Abstract The electrical and gas sensing properties of chemically deposited zinc oxide (ZnO) films were investigated. Two activation energy values, 0.3 eV and 0.8–0.9 eV, were determined in the temperature range 300–400 K which are attributed to oxygen vacancy (VO) donor and heat of chemisorption of the O2− species. The adsorption of oxygen on ZnO leads to a stable and highly resistive surface suitable for sensor operation in the resistive-mode. A high sensitivity (S>99%) is observed for 3 vol% hydrogen (H2) in air along with a strong surface reduction. For liquid petroleum gas (LPG), a high sensitivity (S=50–75%) is observed in the 0.4–1.6 vol% concentration range in air which is an important commercial range for LPG alarm development.

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