Simulation Of Micro-structural Gas Sensor And Study Of The Ethanol Gas Sensor

Gas sensors are widely used in agriculture, home life and air quality monitoringand other fields. Recently along with the gradually prevalence of Microelectronictechnology, miniaturization and integration have become the development direction ofthe sensor. Micro structure gas sensor whose characteristics are small dimension, easyintegration and multi-functional finds more and more favors in many scientists’ eyes.The paper include the structure design of micro hot plate that is a important part of themicro gas sensor and simulate thermal field. Then determine the relative optimizationof the micro hot plate electrode structure. Produce ethanol gas sensor and study itswine sensitivity.The main contents are:1. Design the structure of the micro hot plate and select materialsThe overall size of the micro hot plate is2mm x1mm. After comparing wefind temperature difference decline as metal materials’ thermal conductivity reduceand thus select Pt as the heating metal electrode. In the heat transferring respect, SiO₂is superior to SiNx. Determine the layers of the structure is Pt（300nm）—SiO₂（300nm）—Si（300μm）. In view of the snake-shaped electrode, design coplanar and double–straight type electrodes that could avoid parasitic electric field and overcome theinterference of signal.2. Simulation and analysis of the micro hot plateSimulation and analysis of the MHP’s temperature distribution with differentelectrode width, different gap.Then determine the heating electrode width is100μm,detection electrode and gap widths are35μm and70μm.In this model, MHP’s centertemperature is high and temperature distribution is relatively uniform.3. Optimization of the MHPCorrosive the substrate and plus a silicon island to reduce the helpless loss. After the final optimization, get a new kind of micro gas sensor model. The model’s globaltemperature difference is1.794K, and isothermal zone account for the33.39percentage of the entire surface, active zone’s proportion is44.06%. Response time is32ms, and power consumption is57.6mw.4. Preparation of ZnO flower-like NanomaterialAggregate pure flower-like ZnO nanostructure materials are synthesized througha sample hydrothermal method. After phase analysis, it is indicated that the sample ishexagonal momocrystal wurtzite structure. Every bundle is composed of closelypacked nanorods with average diameters of150nm and length of1μm.The growth ofZnO is along the c axis, corresponding to the [0001] direction.5. Preparation of the ethanol gas sensor and study its wine sensitivityThe thick film heater type micro gas sensor with ZnO samples is studied.（1） The sensitivity of the sensor to500ppm ethanol is89.5at an operated temperatureof250°C and the sensitivity of ZnO flower-like Nanomaterials is3.3times higherthan the conventional powder ZnO. ZnO flower-like Nanomaterials’ sensitivity toethanol significantly improve.（2） The sensor’s response time is5s, and recovery time is about9s to ethanol. Thecomponent show a good stability and reproducibility.（3） The sensitivity of the sensor increase as the gas concentration larger. Whenethanol is5000ppm, it reach the maximum sensitivity251.（4） The sensor is not sensitive to H₂，NO，CO，NO₂，C₆H₅CH₃, and it’s lowersensitive to NH₃. The sensitivities toCH₃COCH₃and C₂H₅OH are127.3and258.4. Therefore the component has excellent selectivity, and it reach thepractical conditions.