| Oxygen is most important for human beings survival.The concentration of oxygen in the air affects human health to a great extent.In addition,detecting the concentration of oxygen in the exhale gas could evaluate the health status of human body.With the development of gas sensor,the demand for integration in portable devices was also increasing.At present,commercial oxygen sensors are generally based on electrochemistry,which is difficult to integration,high power consumption and poor stability.In contrast,oxygen gas sensors based semiconductor have been widely studied because of their advantages of integration and small size.However,most research of semiconductor based oxygen sensor were carried out in vacuum or inert gas atmosphere,and need high temperature heating,the power consumption is still high.If used in the air(oxygen content 21%),the performance of these sensors will be greatly reduced,or even failure.Therefore,it is necessary to develop an integrated and low-power oxygen sensor suitable for air atmosphere.The main work is as follows:(1)Preparation of Sn O2 films by sputtering followed by oxidation(first sputtering tin film and then oxidizing to Sn O2 film at high temperature)and the effects of oxidation temperatures and film thickness on the film structure were studied.The morphology,crystal structure and chemical composition of the samples were characterized by SEM,TEM,XRD,XPS and EDS.It is found that the oxidation temperature in growth Sn O2 thin films has a great effects on the morphology and crystal structure of the samples.The Sn O2 thin films grown by oxidizing110nm tin at 800?have the highest oxygen vacancy content.(2)The influence of heating temperature and ultraviolet light on the performance of the sensor was studied.The sensor has no response to oxygen without UV illumination,while could detect oxygen under UV illumination.The response time is reduced from 625 s to 480 s as the operating temperature increased to 60?.(3)The effects of oxidation temperature and film thickness on gas sensitivity of Sn O2 films were studied.It was found that the oxidation temperature had a great effect on the sensitivity which is increased by 3.5 times through the optimization of the oxidation temperature,while the response time of the sensor is greatly affected by the thickness,which is shortened by 1.3times through the optimization of the thickness.The optimum oxidation temperature and optimum thickness of Sn O2 were 800?,110 nm respectively.(4)The detection limit of the Sn O2 thin film for oxygen reaches 1%,and it has good repeatability,selectivity and long-term stability(resistance value changes 1.29%after two months,sensitivity changes<2%).The analysis shows that the oxygen vacancy content is the main factor affecting the sensitivity property,in addition,the morphology and crystal structure of the film also have a certain influence on the sensitivity property.(5)In order to make a comparison with the traditional reactive sputtering process.This method was used to prepare Sn O2 films(direct deposition of Sn O2 films),and its sensitivity to oxygen was tested.Comparing with the above method of coating and then oxidation,the reaction sputtering Sn O2 thin film sensor has a longer response time(>15 min)and poor selectivity.Based on researches above,Sn O2 oxygen sensor prepared by sputtering and then oxidation method could detect oxygen at room temperature,and has good sensitivity,repeatability,selectivity and long-term stability,which has a certain practical and commercial application value. |
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