【作者】 李云涛；

【导师】 程纲； 杜祖亮；

【作者基本信息】 河南大学 ， 凝聚态物理， 2012， 硕士

【摘要】 气体传感器是一种能检测不同种类与不同浓度气体，并将这些参量转化成电信号输出的装置，广泛应用于环境调查、国家安全、食品加工、医疗诊断等产业中。随着科技的发展，人们对气敏传感器的灵敏度、工作温度等各项性能指标提出了更高的要求，这就需要不断进步的纳米科技对气敏传感器性能加以改善，提高气体检测灵敏度，降低工作温度。在市场上的几种类型的传感器中，由于氧化物半导体传感器具有灵敏度高、使用寿命长、对多种气体敏感和成本低等优点，得到了广泛的应用，金属氧化物半导体例如二氧化锡（SnO₂），氧化锌（ZnO）和三氧化钨（WO₃）是最常用的固体传感器材料。气敏传感器的性能与敏感材料暴露在外的表面积有直接关系，纳米线有比较高的比表面积，存在非常丰富的表面态，有比较高的氧化活性，相比其块体材料来说有较高的灵敏度，和较低的工作温度，同时纳米线气体传感器还有利于减小尺寸进而降低能耗，所以纳米线是设计下一代传感器的理想候选结构材料。基于肖特基势垒的纳米传感器在气敏传感器中展现出优异的气敏性能，用肖特基接触代替欧姆接触是提高气体灵敏度的重要方法，基于单根纳米材料肖特基势垒气敏传感器逐步得到研究人员的重视。本论文系统研究了基于肖特基势垒的单根SnO₂纳米线气体传感器的气敏特性，通过气敏性质的测试发现在室温下对100ppm H₂S灵敏度高达1238，并且具有良好的重复稳定性。利用溶胶-凝胶与热蒸发相结合的方法制备了SnO₂纳米线，并对所得样品进行了结构和形貌表征，得出我们合成的纳米线具有单晶金红石结构。用电场组装技术制备了单根SnO₂纳器件，通过测试器件I-V曲线，得出纳米线两端与金电极均形成了肖特基接触，构成了背靠背肖特基势垒结构。我们还对可能的气敏机理进行了分析，在这种背靠背肖特基势垒结构中，器件的电流受反向肖特基势垒控制，势垒高度受氧的吸附脱附调控，电流随着势垒高度变化呈现指数变化规律，这是我们的器件在室温下有超高的气体检测灵敏度的主要原因；SnO₂纳米线有比较多的表面氧空位缺陷，吸附在氧空位处的氧O₂-会转化为O-，而O-比O₂-有更高的反应活性，这是我们的器件在室温下具有超高气体灵敏度的另一个原因。具体研究内容如下：第1章对一维纳米材料气敏传感器研究进展进行了介绍。重点介绍基于单根纳米线肖特基势垒型的气敏传感器以及室温气敏传感器，并以此为基础明确了本论文研究选题，目的和主要研究内容。第2章介绍了通过溶胶凝胶与热蒸发法高温合成SnO₂纳米线的具体方法和详细的实验过程。通过控制生长条件，成功合成了SnO₂纳米线。并对纳米线进行了一系列的表征，主要包括X射线衍射（XRD）、扫描电子显微镜（SEM）、透射电子显微镜（TEM），高分辨透射电子显微镜（HR-TEM）对样品的表面形貌、结构及成份进行表征和研究。通过电场在位组装的方法成功制备了单根SnO₂纳米线原型气敏传感器。并且分析研究了退火对单根SnO₂纳米线的输运性质影响。第3章系统研究了单根SnO₂纳米线肖特基势垒气体传感器的气敏特性，通过测试传感器对H₂S的在不同温度下、以及多周期的气敏特性，系统研究了传感器对硫化氢的气敏特性。得出在室温下对100ppm H₂S的灵敏度高达了1238，并且具有良好重复稳定性，通过分析实验结果，讨论了可能的气敏机理。更多还原

【Abstract】 Gas sensor is a kind of device that can detect gas with different types and different concentration,and transform these parameters into electrical signal. It is widely used in environmental investigation,national security, food processing, medical diagnosis and various other industrial applications. With thedevelopment of science and technology, higher requirements are put forward for various performanceindicators of gas sensors, which need the developing nanotechnology to improve performance, such asimproving the sensitivity of measurement of gas and reducing working temperature. Among the severalvarieties of gas sensors available in the market, oxide semiconductor sensors are the most popular owing totheir high sensitivity, long service life, and lower-cost. Semiconducting metal oxides such as tin oxide（SnO₂）, zinc oxide （ZnO）, and tungsten oxide （WO₃） are routinely employed as active materials in thesesensors. The performance of gas sensors has a direct relation to exposed superficial area of sensitivematerial. Nanowire has relatively high specific surface area, various surface states, higher oxidative activity,so it has high sensitivity, and lower working temperature than block material. Besides, Nanowires gassensor can decrease the size and reduce energy consumption, so nanowire is the ideal candidate structuralmaterials for the designing of next generation of sensor. Nanosenser based on Schottky barrier showsexcellent performance in gas sensors, it is an important method to improve gas sensitivity using Schottkycontact instead of ohmic contact. Schottky barrier gas sensors based on single nanometer materialsgradually get the researchers’ attention.In this thesis, the gas sensing properties of single SnO₂nanowire based on the Schottky barrierwas discuss. Through the test of gas sensing properties of H2S, it demonstrated ultra-high sensitivity ofH2S at room temperature. The sensitivity of H2S with a concentration of100ppm comes up to1238, andhave a good repeated stability. SnO₂nanowires are prepared by the method of sol-gel and thermalevaporation. The structure and morphology are characterized, and we get that the nanowires we obtainedhave a structure of single crystal rutile. Electric field assembly technique was used to prepared single SnO₂nanodevice. Through testing the I-V properties, we get that both ends of nanowire are formed the schottky contact with the gold electrodes, constituting back-to-back Schottky barrier structure. We also analysisedthe possible air sensitive mechanism. In this back-to-back Schottky barrier structure, the current of devicewas controlled by reverse schottky barrier, the height of barrier was regulated by adsorption and desorptionof oxygen, current changed exponentially with the changed of barrier height, which is the main reason whyour device have high gas detection sensitivity at room temperature. SnO₂nanowires have more surfaceoxygen space defects. The O₂^-adsorbed on oxygen vacancy translate into O-, O-have higher reactivitythan O₂^-, which is the second reason to explain our device have high gas detection sensitivity at roomtemperature.In Chapter1we introduced the research progress of one-dimensional nanomaterials gas sensor.Focusing on the gas sensor based on single nanowires Schottky barrier, as well as gas sensors at roomtemperature. Based on these we selected the topic and purpose of this thesis, and the main contents.In Chapter2we describe the specific methods and the detailed experimental procedure of SnO₂nanowires by the method of sol-gel and thermal evaporation. The SnO₂nanowires was successfullysynthesized by controlling the growth conditions. The structure and surface morphology of SnO₂nanowireswere characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmissionelectron microscopy （TEM） and high-resolution transmission electron microscopy （HR-TEM）. Single SnO₂nanowire gas sensors were successfully prepared via the electric field assembly method.In Chapter3we studied the gas sensing properties of single SnO₂nanowires through the testingof sensing properties for H2S at different temperature. The sensitivity of H2S with a concentration of100ppm comes up to1238. The mechanism of gas sensor was discussed by analyzing the transport mechanismof the Schottky barrier. And a series of assisted experimental was done to prove it. The gas sensormechanism of single nanowires with begeneration of high sensitivity and high selectivity room temperaturenanometer sensor based on single nanowires was also discussed.更多还原