Research Article

Design and Fabrication of Humidity Sensors Based on Ceramic Thin Films

Wei-Cheng Huang 1, Yun-Cheng Li 1, Sutatch Ratanaphan 2, Lung-Ming Fu 3, Chia-Yen Lee 1 *
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1 Department of Materials Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan2 Department of Tool and Materials Engineering, King Mongkut’s University of Technology Thonburi, Bangkok 10140, Thailand3 Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan* Corresponding Author
Applied Functional Materials, 5(2), June 2025, 8-17, https://doi.org/10.35745/afm2025v05.02.0002
Published: 30 June 2025
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ABSTRACT

This research utilizes Micro-Electro-Mechanical Systems (MEMS) technology to develop a resistance-based humidity sensor fabricated on an aluminum oxide (Al2O3) substrate. Microfabrication techniques are first employed to pattern the temperature and humidity sensing electrodes on the Al2O3 substrate. Electron Beam Evaporation (EBE), followed by a lift-off procedure, is then used to pattern platinum (Pt) and chromium (Cr) electrodes for temperature and humidity sensing, respectively. Finally, radio frequency (RF) sputtering is performed to deposit thin layers of titanium dioxide (TiO2) and tungsten trioxide (WO3) on the electrodes as sensing layers. The working temperature and humidity are measured concurrently by monitoring the resistance signals of the device using LabVIEW software. The effects of the sputtering and annealing times on the structures of the two ceramic films are explored. In addition, the corresponding changes in the temperature and humidity sensing performance are evaluated and compared. The results show that the TiO2 film has a better moisture expulsion capability than the WO3 film. Consequently, the sensor incorporating the TiO2 film shows a superior sensitivity and faster response time. The maximum sensitivity is observed in the sample annealed at 450°C for 4 h owing to the formation of optimally-sized pores that enhance moisture absorption and removal.
Keywords: humidity sensor, MEMS, titanium dioxide, tungsten trioxide

CITATION (APA)

Huang, W.-C., Li, Y.-C., Ratanaphan, S., Fu, L.-M., & Lee, C.-Y. (2025). Design and Fabrication of Humidity Sensors Based on Ceramic Thin Films. Applied Functional Materials, 5(2), 8-17. https://doi.org/10.35745/afm2025v05.02.0002

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