| In this paper, through introduction of the study of the history as well as the current situation of conductivity and gas sensing properties of medal oxide, the author tries to make a point that " Toward innorvations of gas sensor technology" has long been an urgent requirement both at home and abroad. In the mid-1990s, China started "trying to use metal oxide thin film gas sensors to replace the technological transformation of TGS (porcelain tube, hand paint, sintering, thick film) gas sensors," and in2011began the pilot production of thin film sensors (SnO2, ZnO).The topic in this paper—the development of new thin film gas sensors, is one of the subjects put forward during the pilot production. Its purpose is to find a kind of thin film sensors with better properties, and to finalize the design development of photolithography technique of thin film sensors "combined with sputtering".Fe2O3is n-type metal oxide of Eg=2.1eV, and according to "the theory of developing gas sensitive base material", this is a kind of gas sensitive base material which can be developed. At the same time, there is no Fe2O3metal-oxide thin film gas sensor.The author points out in the introduction of "basic knowledge" that any type of metal oxide gas sensitive base material can be developed into two types of gas sensors: first, conductive gas sensor; second, gas sensor with temperature change. This paper studies Fe2O3, a type of thin film conductive gas sensor.We are using "a plan of Al stripping agent based on a combination of photolithography technique and sputtering" to develop Fe2O3thin film conductive gas sensor. The paper shows the block diagrams and schematic diagrams of its technological process, and makes necessary instructions for related technology.We used Al stripping agent plan in one of the practice of photoetching, and it has proved that this is a useful plan for photoetching, to which the key is to completely get rid of Al basilar membrane in stripping, and the key to the second photoetching is to remain gas sensitive layer (Fe2O3) in the removing of photoresist. In order to achieve this, the stripping time can not be too long.As for the test of thin film gas sensor, we adopt a relatively simple method of "testing in closed chamber and pinhole injection of artificial air (with a concentration of the reducing gas)". Content of the test comprises:(1) gas sensing properties:a curve showing gas sensing properties f C2and CO;We found from the curve that Fe2O3/2%CeO2is a kind of alcohol sensor (C2H5OH) with good selectivity, and its working temperature is higher than500℃.(2) thermal characteristics:mainly identifying the working temperature (t0) in the condition of Ph (heat power dissipation)=Vh·IhThe temperature t0can be referred to the curve t℃～Ph showing temperature consumption characteristics.(3) alcohol sensing properties:tested with function recorder in artificial air with300ppm[C2H5OH]and 300ppm[gasoline]The characteristic parameters of Fe2O3/2%CeO2thin film gas sensor are as follows:Sensitivity(Sn):3～4;Selectivity(Sl):2.5;Response time(τs)<3s;Recovery time(τc)<5s... |
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