Study On Fabrication Technology Of Metal Oxide Coplanar Gas Sensor

Metal oxide gas sensors occupy a decisive position for its fast response and recovery time, high sensitivity, low cost and so on. But the weak selectivity limits the using of metal oxide gas sensors. Fabricating gas sensor array is a good method to solve this question. However, this method requires high consistency of sensing films, good performance of electrode and technics. Especially the extensively used method Screen printing, there are many problems need to be solved.In this paper, 250, 350 and 400 eyes nylon cloth were used to make blocks of printing. The best cloth was selected by researching the shape of pattern and consistency of resistance of electrodes, heaters and gas sensing films printed by different blocks. The 350 eyes nylon cloth had the best performance not only in the shape of pattern but also in the consistency of resistance. However, the products printed by 400 eyes stainless steal cloth had a good performance not only on the shape of pattern but also on the consistency of resistance compared with 400 nylon cloth.The structure of electrode was optimized. First, the length of interdigital electrodes was changed to get the relationship between the resistance of gas sensing films and the length of electrodes. Then, these films were used to test the 300ppm gas of alcohol. The relationship between the length of electrodes and sensitivity of films was got. In the end, the magnetic field distributed in the gas sensing films was imitated by ANSYS, the effect of the discharge in different electrode was researched. And the reason of sensitivity changed by length of electrodes was resolved by this.In order to simplify the technology of printing gas sensor array and optimizing the best selectivity gas sensor array, the injection method was original created in this paper. A kind of porous sponge-like thick film was obtained by printing and parching the ZnO thick film. Then, 0.01mol/L solutions of AlCl₃, CuCl₂, SnCl₄, TiCl₄, PdCl₂ and WCl₆ were deployed and injected onto the zinc oxide thick films. In the end, the films of gas sensor arrays were obtained by sintered for 2h at the temperature of 600℃. The images of FE-SEM shows nanowires appeared on the surfaces of the films which were injected respectively by solutions of CuCl₂, AlCl₃, SnCl₄ and PdCl₂. By testing the gas of alcohol, the best selectivity gas sensor array, ZnO films injected with 0.2μLAlCl₃,0.1μL CuCl₂,0.3μLAlCl₃ and 0.2μL WCl₆ solutions, was obtained with calculating the value of Sum of Euclidean distances(SED).