Clean Technology 2008
Y.D. Kim, B.B. Jung, H.K. Lee, K.H. Lee, H.C. Park
Pohang University of Science and Technology, KR
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.