Generation of oxygen vacancies in ZnO nanorods/films and their effects on gas sensing properties

The ethanol gas sensing properties of ZnO films and ZnO nanorod arrays that had been pretreated with H2O2 and annealed were examined. ZnO films were grown by sputtering, and ZnO nanorod arrays were synthesized on the sputtered ZnO films through a simple hydrothermal method. The ZnO nanorod gas sensors exhibited highly enhanced responses compared to the ZnO films due to the higher surface areas of the former. H2O2 pretreatment and annealing generated oxygen vacancies on the ZnO surface. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and diffused reflectance spectroscopy (DRS) methods were used to characterize the oxygen vacancies on the ZnO surfaces. The induced surface oxygen vacancies enhanced the gas sensing responses. The gas sensing mechanism in the ZnO-based gas sensor was discussed in terms of the effects of the oxygen vacancies. (C) 2014 Elsevier B.V. All rights reserved.