ABSTRACT:
Humidity and moisture sensors play important roles in industrial process control, environmental monitoring, aerospace, pharmaceutical manufacturing, energy infrastructure, and semiconductor fabrication applications. The properties of the humidity-sensitive dielectric layer are important to the performance of these sensors. Anodic Spark Deposition (ASD) is a specialized fabrication technique for producing a highly porous, chemically stable α-Al₂O₃ film, which has been shown to be useful for fabricating a high-performance moisture sensor. ASD is a technique that enables direct electrochemical oxidation to form porous ceramic coatings on substrates (graphite, glass, titanium, aluminum, and so on) under spark-discharge conditions. The α-Al₂O₃ films formed have good thermal stability, corrosion resistance, mechanical strength, and controlled pore structure. This article provides a summary of the principles of ASD, pore formation mechanism, process parameters, and the resulting microstructural characteristics. Special focus on the application of porous alumina produced from ASD in capacitive humidity and moisture sensors. The effects of pore-size distribution, surface morphology, adsorption/desorption kinetics, response speed, sensitivity, and long-term stability are considered. Hybrid α-Al₂O₃/SiO₂ dielectric structures have also been reviewed recently.

Keywords: Anodic Spark Deposition, Alpha Alumina, Humidity Sensor, Moisture Sensor, Porous Ceramics,

How to Cite this paper?