Technical Proceedings of the 2008 Clean Technology Conference and Trade Show

Clean Technology 2008

Chapter 9: Environmental & Sensor Technologies

Y.D. Kim, B.B. Jung, H.K. Lee, K.H. Lee, H.C. Park
Pohang University of Science and Technology, KR
658 - 661
anodic aluminum oxide, pore, humidity
AAO(Anodic Aluminum Oxide) film is fabricated as a sensing material of capacitive humidity sensors. Because AAO films have a lot of nano-size pores, many water vapors can be absorbed. The size of a pore diameter is 80nm. Rectangular spiral-shaped type and interdigitated type are designed and fabricated as electrode types. A micro heater is also integrated because condensed water vapors and contaminants should be evaporated. Using heater, we can improve linearity and reliability and we can reduce hysteresis largely. As a porous layer thickness increases, a sensitivity become higher. That means a thick porous layer can absorb more water vapors. But a response time also increases as a porous layer thickness increases. A sensitivity of rectangular spiral-shaped type is higher than that of interdigitated type. And a response time of rectangular spiral-shaped type is faster than that of interdigitated type. But a hysteresis is independent of electrode type. The experiment using heater shows a good linearity with a small hysteresis for the relative humidity. The condition is the interdigitated type with a 50 porous layer under the electric power of 7v(749mW) . Under this condition, we don’t need a additional linear modification.
Anodic aluminum oxide-based capacitive humidity sensor integrated with micro-heater