title: Positive impedance humidity sensors via single-component materials.
abstract: Resistivity-type humidity sensors have been investigated with great interest due to the increasing demands in industry, agriculture and daily life. To date, most of the available humidity sensors have been fabricated based on negative humidity impedance, in which the electrical resistance decreases as the humidity increases, and only several carbon composites have been reported to present positive humidity impedance. However, here we fabricate positive impedance humidity sensors only via single-component WO3-x crystals. The resistance of WO3-x crystal sensors in response to relative humidity could be tuned from a negative to positive one by increasing the compositional x. And it was revealed that the positive humidity impedance was driven by the defects of oxygen vacancy. This result will extend the application field of humidity sensors, because the positive humidity impedance sensors would be more energy-efficient, easier to be miniaturized and electrically safer than their negative counterparts for their lower operation voltages. And we believe that constructing vacancies in semiconducting materials is a universal way to fabricate positive impedance humidity sensors.
authors.affiliation: School of Engineering and Technology, China University of Geosciences, Beijing 100083, P. R. China.|State Key Laboratory of Information Photonics and Optical Communications, and School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, P. R. China.
authors.forename: Jingwen
authors.initials: J
authors.lastname: Qian
authors.affiliation: School of Engineering and Technology, China University of Geosciences, Beijing 100083, P. R. China.
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Peng
authors.affiliation: School of Engineering and Technology, China University of Geosciences, Beijing 100083, P. R. China.|State Key Laboratory of Information Photonics and Optical Communications, and School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, P. R. China.
authors.forename: Zhenguang
authors.initials: Z
authors.lastname: Shen
authors.affiliation: School of Science, China University of Geosciences, Beijing 100083, P. R. China.
authors.forename: Zengying
authors.initials: Z
authors.lastname: Zhao
authors.affiliation: School of Engineering and Technology, China University of Geosciences, Beijing 100083, P. R. China.
authors.forename: Guoliang
authors.initials: G
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Information Photonics and Optical Communications, and School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, P. R. China.
authors.forename: Xiuli
authors.initials: X
authors.lastname: Fu