Research And Fabrication Of Carbon Nanotube Based Ionization Micro Gas Sensor

Ionization gas sensors are working on ionization of gas molecular since the partial strong electrical field. Based on the breakdown voltage's finger print character, each gas can be identified by its unique ionization or breakdown voltage. Ionization gas sensors have much shorter response time, better sensitivity, and shorter recovering time than the normal absorption sensors.We have demonstrated here a MEMS based ionization micro gas sensor with these works:1) The sensor is working on the ionization principle, which means it would not be affected by the affinity energy and chemistry absorption properties of gases; on the contrary, it would be equipped with shorter response time, better sensitivity, and shorter recovering time;2) We have used CNT (Carbon Nanotubes) as the functional material in the electrodes, there would be greater electrical field and lower working voltage because of the one-dimensional structure and negative electron affinity of CNT;3) DBD (dielectric barrier discharge) principle has been introduced to the device, experiments results prove that it could increase electrical field and reduce the working voltage;4) We have concluded a method of deposition Nickel-coated-CNTF (Carbon Nanotube Film) as the fundamental of fabrication of CNT based ionization device. Experiments results prove that the Nickel-coated-CNTF has flat surface, controllable density, uniform arrangement, better performance of field emission, and could be integrated with MEMS processes easier.5) We have designed and fabricated two structures of micro electrode device. The advantage of using MEMS processes and Nickel-coated-CNTF deposition method ensures the device has shorter distance between the electrodes and higher electrical field, which makes it's possible to ionization 8 gases under a working voltage less than 36V. Based on this fingerprint principle, the device could successfully identify these 8 different gases. Besides that, we also concentrate on the property of the response on human breath and on mixed organic gases.