Preparation And Properties Of Gas Sensor Arrays

A single gas sensor exhibits cross-sensitivity while detecting multi-component gas mixture, which is that a gas sensor is sensitive to more than one kind of tested gas However, combined with pattern recognition technology to analyze the output response, a gas sensor array composed of several elements with different gas sensing properties could achieve excellent selection and high precision measurement. The fabrication and sensing performance of the gas sensor array were investigated in this paper.Firstly, gas sensor units were fabricated by microelectronics technology, which included chips based on Al electrode by means of lithography-corrosion, and chips based on Au electrode through the way of lithography-stripping. As for each chip, the P-type(100) silicon was selected as substrate, silicon oxide as insulating layer, interdigital as electrode structure. The specific parameters of the prepared chips were as followed: width of approximately 50μm, spacing of about 50μm, length of more or less 2000μm, and interdigital logarithm of 30. And then PVP(polyvinyllrrolidone)-MWCNTs(Multi-walled carbon nanotubes) composite materials were sprayed on two groups of chips to compare their gas sensing response on methyl alcohol. Through comparing and analyzing the response curve and linear fitting curve, it is concluded that gas sensors based on Au electrode showed better performance and stability. According to the results, the basic functional structure of the gas sensor array with 2×3 elements and 15mm×17mm size was fabricated. In the manufacture process of the array, lithography process was discussed in specialty. Based on the graphics reversal principle of photo resist AZ5214, a series of experiments were designed to explore the exposure time, pan exposure time and developer time. The results exhibited that the optimal parameters were as follows: the exposure time set as 0.5s, the pan exposure time set as 68 s and the developer time set as 60 s. Under that condition, electrode pattern with appropriate size, much trimmer edges and less pattern defects could be obtained.Finally, the gas sensing performance of the prepared gas sensors were tested. As for the sensor units, the sensing response, the repeatability, the long-term stability and the selectivity were analyzed, respectively. Combined with the surface and section morphology of the sensing films observed by scanning electron microscope, the specific response mechanisms were discussed preliminary. As for the sensor array, six kinds of sensing materials including SnO2-MWCNTs、PEO( Polyethylene oxide)-MWCNTs、PVP-MWCNTs、Pt-MWCNTs、RGO( Reduction of graphene oxide) and CuCl-SWCNT( Single-walled carbon nanotubes) were sprayed on the six independent units by the use of masks. According to the gas sensing response, it is found that the prepared sensor arrays exhibited good gas sensing properties.