基于碳纳米管和氧化铁异质结构的气体传感器研究

发布时间：2018-01-23 00:21

  本文关键词： 微热板 ANSYS CNT@α-Fe_2O_3异质结构 气体传感器　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：在气体传感器领域,金属半导体氧化物(MOS,Metal Oxide Semiconductors)气体传感器因具有灵敏度高、选择性可调、可靠性高、全固态等特点,一直是本领域的研究热点。然而,不断提高的环境标准以及传感器特殊的使用环境对传感器的性能提出了更加严苛的要求。目前,虽然基于旁热式器件结构的半导体氧化物气体传感器研究已经取得较大进展,但是如何进一步提升传感器对待测气体的灵敏度和选择性,降低传感器的检测下限和功耗仍然是该类传感器面临的重大挑战。针对上述的关键科学问题,本论文从两方面展开研究,首先是器件结构的设计与开发,具体是利用MEMS((Micro-Electro-Mechanical System)技术制作微热板式器件,实现功耗的降低。其次是高性能敏感材料的设计与构筑,具体是采用简单的液相合成技术制备出CNT@α-Fe_2O_3复合异质结构气敏材料,利用复合材料的结构优势和不同气氛下异质结势垒高度变化,实现传感器灵敏度的提升。具体研究内容如下:在器件结构设计和制作方面,我们设计并制作了基于MEMS((Micro-Electro-Mechanical System)技术的微热板(MHP,Micro hot-plate)式器件。利用ANSYS有限元分析对MHP进行了热稳态及热应力分析,讨论了加热电极的形状和背面硅层等因素对MHP悬膜温度分布的影响。通过优化结构设计,确立MHP采用蛇形加热电极,背部保留0.5μm的硅层,器件的整体尺寸为2.0 mm×2.0 mm×0.4 mm。此后,利用MEMS工艺通过外协加工制作了悬臂梁式MHP,并用红外热像仪对其进行了实际性能测试。测试结果显示,MHP的热场分布较均匀,高温区主要集中在悬膜区,实际MHP的加热效率约为4.7℃/m W,实现低功耗。在高效敏感材料构筑方面,结合α-Fe_2O_3优异气敏特性和碳纳米管(CNT)大的比表面积及高的机械强度,利用简单的液相合成技术制备出CNT@α-Fe_2O_3异质结构复合敏感材料。电镜结果表明CNT@α-Fe_2O_3是一种以CNT为骨架,多晶的α-Fe_2O_3纳米棒在其表面自组装而成的一种棒状异质结构,长度约为几个微米,直径约500 nm左右。相比于单一的α-Fe_2O_3纳米棒,CNT@α-Fe_2O_3复合异质结构具有更大的比表面积,从而增加表面吸附氧能力。CNT@α-Fe_2O_3复合材料气敏特性测试结果表明。相比于单一α-Fe_2O_3结构,碳纳米管的引入大幅度增强了复合异质结构CNT@α-Fe_2O_3传感器对丙酮的敏感特性。在225℃下CNT@α-Fe_2O_3传感器对100 ppm丙酮的响应达到了34.6,检测下限达到500 ppb,且具有快的响应时间和良好的稳定性。此外,基于CNT@α-Fe_2O_3复合异质结构的微热板式气体传感器,相比旁热式器件,其对丙酮的灵敏度和选择性基本保持不变,但是其功耗在225℃时仅为44 m W,约为旁热式器件的1/10(460 mW)。
[Abstract]:In the field of gas sensors, metal semiconductor oxide Oxide semiconductor sensors have high sensitivity and selectivity. High reliability, all solid state and other characteristics, has been the research hotspot in this field. However, the increasing environmental standards and the special use environment of the sensor put forward more stringent requirements on the performance of the sensor. Although much progress has been made in semiconductor oxide gas sensors based on side-heat devices, how to further enhance the sensitivity and selectivity of the sensors to gas measurement. Reducing the detection limit and power consumption of the sensor is still a major challenge for this kind of sensors. Aiming at the key scientific problems mentioned above, this paper studies from two aspects, the first is the design and development of the device structure. MEMS((Micro-Electro-Mechanical system technology is used to fabricate micro-hot plate device. The second is the design and construction of high performance sensitive materials, and the preparation of CNT @ 伪 -FeS2O3 heterostructure gas sensing materials by simple liquid phase synthesis technology. The sensitivity of the sensor can be improved by using the structure advantage of the composite material and the change of the barrier height of the heterojunction in different atmosphere. The specific research contents are as follows: in the aspect of device structure design and fabrication. We have designed and fabricated the micro hot plate based on MEMS((Micro-Electro-Mechanical system technology. Micro hot-plate device. The thermal steady state and thermal stress of MHP are analyzed by ANSYS finite element analysis. The influence of the shape of the heating electrode and the silicon layer on the temperature distribution of the MHP suspension film was discussed. By optimizing the structure design, the snake-shaped heating electrode was adopted in MHP and the silicon layer of 0.5 渭 m was retained in the back. The overall size of the device is 2.0 mm 脳 2.0 mm 脳 0.4 mm. After that, the cantilever MHP is fabricated by the MEMS process. The actual performance of MHP was tested by infrared thermal imager. The results showed that the thermal field of MHP was uniform, and the high temperature region was mainly concentrated in the suspension region. The actual heating efficiency of MHP is about 4.7 鈩，

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