Pd掺杂的SnO2甲烷传感器气敏性能的研究

本文研究了Pd掺杂的SnO2材料对于甲烷气体的敏感特性。首先从机理上说明掺杂Pd金属的原因;然后,采用简单的混合研磨工艺制备了Pd掺杂SnO2复合材料;其次,采用刷涂工艺在加热型平板电极上制备了气敏层。研究了所制备的Pd掺杂SnO2气体传感器在不同温度对甲烷气体的敏感特性。结果表明,Pd掺杂在提高SnO2的气敏性能的同时还能降低其工作温度;其中,2 wt%Pd掺杂SnO2的传感器气敏性能最优,在最佳工作温度(200°C)下对500 ppm甲烷的气敏响应可达3.43,灵敏度提升了45.67倍(50–1000 ppm)。     

Pd掺杂对SnO_2气敏性能的影响

在气体传感器中金属Pd被广泛用作的催化剂,利用直流溅射和浆料涂覆的方法制备出SnO2气敏元件,在氧气氛中通过直流溅射对SnO2元件进行Pd掺杂,并对用不同制备方法所得元件的电导、灵敏度等进行比较。结果表明:Pd掺杂降低了元件的电导,并使得电导峰出现的位置从460℃转移到260℃和180℃,这和样品的制备方法有关。Pd掺杂有利于提高SnO2元件的灵敏度,特别在低温区(100~250℃)对不同气体的灵敏度有几十倍提高。     

温湿度对SnO2基CO气体传感器敏感特性的影响

采用溶胶-凝胶法制备了纳米SnO2粉体及Pd掺杂浓度比分别为0.2 mol%、2 mol%1、0 mol%的三种掺杂粉体。以制得的粉体作为敏感材料,制成陶瓷微热板式CO气体传感器。在自行搭建的气体测试平台上,测试了各传感器在不同环境温湿度条件下对CO的响应,研究了Pd掺杂浓度对传感器湿度稳定性的影响,探讨了湿度影响传感器灵敏度的机理。实验结果表明:0.2 mol%Pd掺杂器件在不同湿度条件下灵敏度离散度由掺杂前的20.5%降低至8.63%,有效提高了传感器的湿度稳定性。10 mol%Pd掺杂器件在湿度大于50%相对湿度时,对20×10-6 CO出现反常响应,在还原气体CO出现时气敏膜电导减小。     

一种自组装型SnO_2纳米线氢传感器

为了能够对低体积分数的氢气进行灵敏探测,提高氢气生产、使用、运输、存储的安全性,通过热蒸发SnO2和活性炭的混合粉末的自组装方式直接在Cr-Au梳状交叉电极上制备了一层SnO2纳米线气敏层,构成了SnO2纳米线气体传感器。经测试,发现此传感器对于体积分数范围为10×10-6~500×10-6的氢气具有良好的探测灵敏度。     

Pd/SnO2/SiO2/Si集成薄膜的结构与气敏性能

采用磁控溅射技术制备Pd/SnO2/SiO2/Si集成薄膜.研究退火处理对薄膜微观结构和表面形貌的影响,进而测试了相关的气敏性能.实验证明,经过氧化性退火处理,集成薄膜中的SiO2层厚度从3 nm增长到50 nm左右,形成Pd/SnO2/SiO2/Si结构,SnO2薄膜形成金红石结构的多孔柱状晶.气敏测试表明,Pd/SnO2/SiO2/Si集成薄膜在低温区对H2、CH4、CO和C2 H5OH敏感性较高,另外,随着H2气体浓度的增加,相应灵敏度从35递增至73.5.     

基于表面介孔SnO2改性层的高选择性MOS氢气传感器

采用溶胶凝胶法制备了介孔SnO2粉体,通过丝网印刷技术将其印刷在市售SnO2气体传感器表面作为改性层,研究了改性层厚度对氢气选择性的影响。通过对乙醇、丙酮、苯和H2的测试,当介孔SnO2改性层厚度为15μm时,传感器在300℃下对H2的选择系数最大为5.7。同时讨论了改性层提高气体传感器氢气选择性的机理。     

基于SnO2/石墨烯异质结NO2气敏传感器

采用滴涂法和真空退火将纳米二氧化锡负载在单层石墨烯上,制备了SnO2/石墨烯异质结材料,进行拉曼光谱材料表征,研究了SnO2/石墨烯异质结对NO2的气敏特性。结果表明,SnO2/石墨烯异质结相对本征石墨烯在低NO2气体体积分数下灵敏度提升,解吸附时间短,NO2气体体积分数为10×10-6时,0.3mg/mlSnO2纳米溶液/石墨烯异质结传感器比单层石墨烯灵敏度提升近4倍,解吸附时间缩短近9倍。     

纳米薄膜气敏技术发展与展望

目前,纳米薄膜气体传感器的发展趋势是提高灵敏度和工作性能,降低功耗和成本,缩小尺寸,简化电路.介绍SnO2、ZnO、TiO2等主要纳米薄膜气敏传感器研究现状.电子鼻依靠气体传感器阵列而组成,还介绍了装有电子鼻的机器人.     

表面SiO2改性高选择性MOS氢气传感器

以十甲基环五硅氧烷(D5)为硅源,采用化学气相沉积法(CVD)在SnO2气体传感器表面沉积SiO2膜作为改性层,研究了CVD处理过程中温度和处理时间对传感器的选择性和灵敏性影响.通过对乙醇、丙酮、苯和氢气的气敏性能测试,得出在500℃下CVD处理8 h后的SnO2传感器对氢气具有最好的选择性和灵敏性.同时讨论了SiO2改性层提高SnO2传感器选择性和灵敏性的机理.     

SnO2基薄膜气体传感器制作与敏感性测试

在现有的粉末烧结型SnO2基气敏传感器基础上研制了薄膜型SnO2基气体传感器,以抛光的丽热石英玻璃为基片,真空磁控溅射50～70nm厚度的SnO2薄膜,在SnO2薄膜上分别溅射不连续的ZnO、Al2O3、CeO2、InO2等薄膜,传感器背面溅射30μm的Ni80Cr20电阳合金作为传感器加热电阻,用薄膜热电偶测量传感器工作温度。测试了不同的复合瞑对传感器灵敏度和选择性的影响,并对传感器的吸附与解吸速度进行了测试,薄嗅传感器达到相同灵敏度所需的工作温度比粉末烧结型传感器下降100～150℃,吸附解吸速度比粉末烧结型快。     

Characterization of ozone sensors based on WO3 reactively sputtered films: influence of O2 concentration in the sputtering gas, and working temperature

We report on electrical responses of tungsten oxide thin film ozone sensors based on a tungsten trioxide (WO₃)/tin oxide (SiO₂)/Si structure with interdigitated Pt electrodes. The influence of O₂ concentration in the sputtering gas and working temperature of the sensor are investigated. Sensitivity to ozone increases with O₂ content in the sputtering gas. It reaches its highest value for sensors fabricated with 50% O₂. For these sensors, the best ozone sensitivity and shortest response and recovery times are obtained at a working temperature of 523 K. Ozone sensitivity is compared to other ozone sensors.     

二氧化锡纳米粉料的制备及其气敏性能

采用低温等离子体法以无水四氯化锡为源物质制备了二氧化锡超微粉料,TEM照片显示粉料粒度均匀,粒径为10nm量级,并且阴极高压越高,粒径越小。用该粉料制备的气敏元件,测定了气体灵敏度与温度及浓度的关系,显示了比一般无渗杂氧化锡元件灵敏度高的特点,可望开发成为广普型气敏传感器。还讨论了元件的灵敏度和电导温度特性随不同热处理温度的变化。大的比表面积在这种类型传感器运行机制中起着重要作用.     

Development of high sensitivity tin oxide based sensors for gas/odour detection at room temperature

An effort has been made to develop thick film tin oxide gas sensors which could detect various gases/odours at room temperature. To achieve this, the fabricated sensors were annealed in oxygen plasma for various durations. It was then found that, the room temperature sensitivity of such sensors was increased to about ten times as compared to the sensitivity of the non-annealed sensors. Further, plasma annealed sensors are found to be practically independent of temperature and the room temperature sensitivity of these sensors are found to be about 1.5 times the sensitivity of the conventional sensors at its operating temperature of 300°C. Studies on the variation of d.c. resistance, sensitivity, temporal response, current–temperature characteristics and impedance spectroscopy with the annealing time have also been made. These studies reveal that, with the increase in annealing time, there is a permanent gradual reduction in the d.c. resistance of annealed sensors. Further, it is also observed that with the increase in annealing time, the response time improves, barrier height reduces, barrier capacitance increases and the dependence of the sensitivity with temperature reduces while the sensitivity itself improves many-fold.     

High temperature field effect hydrogen and hydrocarbon gas sensors based on SiC MOS devices

The growing need for reliable, efficient, high temperature hydrogen and hydrocarbon monitoring has fueled research into novel structures for gas sensing. Metal oxide semiconductor (MOS) devices employing a catalytic metal layer have emerged as one of the leading sensing platforms for such applications, owing to their high sensitivity and inherent capability for signal amplification. The limited operating temperature of such devices employing silicon as the semiconductor has led research efforts to focus on replacing them with devices based on silicon carbide (SiC). More recently, MOS devices having different oxide layers exhibiting improved sensing performance have emerged. Considering the amount of research that has been carried out in this area in recent times, it is important to elucidate the new findings and the gas interaction mechanisms that have been ascribed to such devices, and bring together several theories proposed by different research groups. In this paper we first highlight the needs which have driven research into SiC based field effect hydrogen and hydrocarbon sensors, illustrate the various structures being investigated, and describe the device evolution and current status. We provide several sensing examples of devices that make use of different oxide layers and demonstrate how their electrical properties change in the presence of the gases, as well as presenting the hydrogen gas interaction mechanisms of these sensors.     

Influence of the doping method on the sensitivity of Pt-doped screen-printed SnO2 sensors

In this work, we study the influence of the introduction method of Pt atoms on the sensitivity to traces of ethanol of Pt-doped SnO₂ sensors. The tin oxide films were obtained by a screen-printing process. Two different methods were employed to introduce Pt atoms on SnO₂ films. In the first one, the Pt atoms were added to the screen-printed tin oxide layer by using RF magnetron sputtering and a subsequent thermal treatment. The second method consisted of mixing SnO₂ and Pt pastes before the screen-printing process. The different active layers (including un-doped tin oxide) were carefully examined relative to their sensitivity to ethanol at different working temperatures. Sensors prepared by the second method showed sensitivity to ethanol four times higher than one of the sensors prepared by the first method and 12 times higher than un-doped sensors. XPS and scanning electron microscopy (SEM) measurements showed that this behaviour could be associated with the spatial distribution of the doping elements within the tin oxide film. While in Pt-sputtered sensors most of the Pt atoms were found at the surface of the active layer, for the sensors made by mixing Pt and SnO₂ pastes, a homogeneous distribution of the Pt atoms was observed. These sensors show high sensitivity and fast response time to ethanol vapours, with a detection limit in the ppb range.     

A tin oxide semiconductor sensor for oxygen determination in the sub-ppm range

Tin oxide sensors are currently used for the detection of reducing gases in air, although an appropriate use of these sensors could also be the detection of traces of oxygen in inert gas. The present work deals with the results of a systematic investigation on the possibility of using tin oxide sensors for the detection of sub-ppm amounts of oxygen in argon, as required by some applications in microelectronics.     

Analysis of the noble metal catalytic additives introduced by impregnation of as obtained SnO2 sol–gel nanocrystals for gas sensors

In order to clarify the role of the noble metal additives in the gas sensing mechanisms, three of the most common catalytic additives, such as Pd, Pt and Au, have been introduced in a sol–gel obtained tin oxide base material. The additives nominal weight concentrations used were 0.2% and 2%, and they were introduced in the precipitated tin oxide. A posterior calcination treatment was carried out, during 8 h, at the temperatures of 250°C, 400°C, 450°C, 600°C, 800°C and 1000°C. Structural and surface analysis of these nanopowders have been performed. Identification and localisation of metallic, 2+ and 4+ oxidised states of the used noble metals are discussed, and experimental evidences about their effects on the sensor performance are presented. Likewise, effects of their presence on the nanoparticle characteristics, and also on the material sensitivity to CO and CH₄, are analysed and discussed.     

表面碳化的硅纳米孔柱阵列的H2S室温电容传感特性

通过将硅纳米孔柱阵列(Si-NPA)进行高温碳化处理,制备出一种SiC/Si-NPA复合纳米体系。对SiC/Si-NPA的表面形貌和结构表征揭示,生长于Si-NPA上的SiC薄膜由具有立方结构的SiC纳米颗粒组成,厚度为～200 nm。SiC/Si-NPA整体上保持了Si-NPA原有的柱状阵列结构特征。对浓度介于0～1 200×10-6的H2S气体的室温传感性能测试表明,SiC/Si-NPA对H2S气体的电容响应灵敏度可高达790%,而其对400×10-6浓度H2S气体的响应和恢复时间则分别为170 s和200 s,元件具有较好的测量重复性和稳定性。SiC/Si-NPA可能是一种室温条件下较为理想的H2S气体传感材料。     

Nanowire structured SnOx–SWNT composites: High performance sensor for NOx detection

A nanowire structured nanocomposite of tin oxide (SnO_x) and a single-walled carbon nanotube (SWNT) are fabricated using rheotaxial growth and thermal oxidation method for gas sensor application. The morphology, gas sensing properties, as well as the chemical and electrical properties are investigated. The oxidation temperature for Sn mainly determines the stoichiometry of the SnO_x nano-beads, and consequently the electrical and gas sensing properties of the nanocomposite sensors. The gas sensing to nitrogen oxide, hydrogen, oxygen, xylene, acetone, carbon monoxide, and ammonia are also examined to determine the gas selectivity of the sensor. The high sensitivity and selectivity towards NO_x of the nanocomposite sensor is realized via the porous structure of the SWNT template. The gas sensing mechanism of the nanocomposite structure is also discussed.