Humidity Sensing Properties Of Iron Oxide / Silicon Nanoporous Pillar Array Composite System

Sensors are being developed to be more intelligent and subminiature presently. This kind of sensors could be obtained by depositing some sensitive semiconductors on a silicon template. Iron oxide is very sensitive to many gases in the air, especially to water; Silicon nano-porous array (Si-NPA) has a special morphology of micron/nanometer structural composite system on the surface, This structure provides not only large surface area to Si-NPA but passing ways to the gases absorbed in the pores on the pillars. Besides, silicon could be integrated compatibility with typical silicon arts in device, so it is could be a excellent template for sensors. Depositing the iron oxide nano-crystal on Si-NPA by spin-coating method, Fe₃O₄ /Si-NPA and γ— Fe₂O₃ /Si-NPA sensors could be obtained.We has done some experiments for this work and the results as below:First, High-pure and size being controlled iron oxide nano-crystal was synthesized by the microemulsion and hydrothermal method.Second, As-prepared nc-Fe₃O₄-containing emulsion was spin-coated on Si-NPA and then sintered in nitrogen or oxygen ambient, Fe₃O₄ /Si-NPA or γ — Fe₂O₃ /Si-NPA sensors could be obtained. The surfaces of these combined materials contained the micron/nanometer composite structure of the template of Si-NPA mostly.Third, the Si-NPA , the Fe₃O₄ /Si-NPA and the γ—Fe₂O₃ /Si-NPA sensors' responses to water were measured in different humid ambient. The results reserved that the Si-NPA exhibits high sensitivity and short response times to water. The Fe₃O₄/Si-NPA sensor exhibits high sensitivity, strong output signal intensity, and short response times. And the γ—Fe₂O₃ /Si-NPA sensor is very sensitive to the humidity, too. Conclusions could be drew based on the analysis to performances of three sensors, that is: the outstanding performance of the Si-NPA sensor has close relation with the micron/nanometer structural composite system on its surface, not caused by the sensitive materials but also the special structure of the sensor's surface. Fe₃O₄/Si-NPA sensor's response to water was donated by the Fe₃O₄ and the Si-NPA together. γ— i-NPA sensor could be enhanced its stability by doping.The iron oxide/ Si-NPA sensors are intelligent and subminiature, and their responses to water are sensitive, so these sensors boost up the research about humid sensor. The micron/nanometer structural composite system of Si-NPA is favorable to gas' absorption and transport, so it could be used as template for other more sensors.