CuO—SnO2半导体陶瓷气敏机理研究

本文根据实验结果，分析了以SnO2为主体材料的CuO作添加剂的CuO-SnO2气敏传感器的敏感性能，并从理论上对其气敏机理进行了探讨。     

半导体陶瓷型薄膜气敏传感器的研究进展

半导体陶瓷型薄膜气敏传感器,具有灵敏度高、与气体反应快、制备成本较低等优点,已经成为近年传感器研究和开发的重点．是未来气敏传感器的发展方向之一。本文介绍了陶瓷型半导体薄膜气敏传感器常见的器件结构、薄膜材料的主要制备方法．部分主要的半导体金属氧化物薄膜气敏材料．以及近期相关的研究进展,并扼要分析了今后的发展方向。     

CuO－SnO_2半导体陶瓷气敏机理研究

本文根据实验结果，分析了以ＳｎＯ＿２为主体材料的ＣｕＯ作添加剂的ＣｕＯ－ＳｎＯ＿２气敏传感器的敏感性能，并从理论上对其气敏机理进行了探讨。     

气敏传感器的近期展望

综合介绍了气敏传感器材料及元件的最新进展,侧重于气敏材料研究工作的概述,并分析了气敏传感器的发展趋势。     

金属氧化物半导体气敏传感器稳定性研究进展

金属氧化物半导体(MOS)气敏传感器的稳定性是气敏器件实用化进程中最具有挑战性的因素。影响器件稳定性的主要因素包括颗粒尺寸、颈部宽度、微裂纹、电极、湿度和温度的变化。颗粒的长大和颗粒间颈部尺寸的变化降低了耗尽层对总电阻变化的贡献;微裂纹的加剧使器件的电阻发生漂移,并且为水蒸气、氧气和待测气体扩散到敏感膜内部提供便捷的通道;电极的退化影响电极与气敏材料之间的接触电阻Rc;温度和湿度的改变使气体的吸附、脱附、反应活性和电子迁移率等都发生变化,因而器件的稳定性得不到保证。在机理分析的基础上,分别介绍了提高器件稳定性的方法。     

气敏传感器的近期进展

综合介绍了气敏传感器材料及元件的最新进展,侧重于气敏材料研究工作的概述,并分析了气敏传感器的发展趋势     

CuO／ZnO复合膜异质结的制备及其湿敏特性

用直流气体放电活化反应蒸发及光刻技术，在普通玻璃衬底上制备出开放式薄膜型ＣｕＯ／ＺｎＯ半导体ｐｎ结，该ｐｎ结的Ｉ－Ｕ曲线呈整流特性，在室温下，正向伏安特性曲线随相对湿度的变化而改变。相对湿度增加，ｐｎ结的正向电流增大，而反向电流的变化可忽略，ｐｎ结的偏压不同，相对湿度变化所引起的电流变化不同。这种湿敏特性是由于对薄膜刻蚀图案形成的开放式ｐｎ结部分暴露天大气的结果。     

ZnO气敏陶瓷的制备与气敏性能研究

分别用氨水、草酸铵、尿素和碳酸钠做沉淀剂合成了4种不同陶瓷微结构的ZnO气敏材料。用X射线衍射(XRD),透射电子显微镜(TEM)和电子衍射(ED)法研究了其晶体和陶瓷微结构。采用静态配气法测试了其气敏效应。ZnO陶瓷具有四方和六方2种不同的结晶外形,颗粒尺寸为0.1～4μM。ZnO陶瓷对C_2H_5OH具有较好的气敏选择性,通过SnO_2的掺杂,ZnO对C_2H_5OH的选择性可进一步提高。颗粒微细化有助于提高ZnO的气体灵敏度。     

氧化物半导体丙酮气敏传感器材料研究与应用

低浓度丙酮气体的检测在监测工业生产、食品质量、畜牧业和疾病等中有重要的作用.综述了近年来氧化物半导体丙酮气敏传感器材料的研究进展,并对传感器材料的形态、制备方法、敏感机理及存在的问题进行了分析,指出了发展方向.     

氧化物半导体气敏传感器的改性研究进展

氧化物半导体气敏传感器具有灵敏度高、制造成本低、信号测量手段简单、使用方便等优点,在有毒有害气体实时监测方面极具应用潜力。综述了新型氧化物半导体气敏感器改性的研究进展、存在的问题及发展趋势。     

Vibrating capacitor method in the development of semiconductor gas sensors

Adsorption usually results in work function shifts on catalytically active surfaces such as semiconductor gas sensors. The purpose of the present article is to summarise the capabilities of the vibrating capacitor from the simplest adsorption-induced work function tests to the scanning, vibrating, capacitor-yielded olfactory pictures and other chemical pictures. After a brief history and review of theoretical bases, the latest results will be discussed in detail. Olfactory pictures from semiconductor surfaces give a new chance to improve the selectivity of gas analysis. Chemical pictures from thin SnO₂ layers produced by atomic layer epitaxy reveal the inhomogeneities of the technology. CPD maps taken from Pd nanolayer (activator)-covered surfaces help to find the best layer-depositing parameters for the activation process of the thin semiconductor gas sensor films.     

Ordered mesoporous ZnO for gas sensing

We report on the synthesis and the gas-sensing properties (CO and NO₂ detection) of mesoporous zinc oxide. A two-step structure replication method for the synthesis is employed. In the first step mesoporous SBA-15 silica is prepared by the utilization of self-organization of amphiphilic organic agents. This mesoporous silica is used as the structure matrix for synthesizing mesoporous carbon CMK-3, which, in turn, is employed for yet another replication step, using zinc nitrate as the precursor. The resulting material is characterized by X-ray diffraction and nitrogen physisorption and its gas-sensing properties are compared with a non-porous ZnO sample.     

Fabrication of p-type CuSCN/n-type micro-structured ZnO heterojunction structures

Micro-sized ZnO rods on a SnO₂ coated glass substrate were obtained by the spray pyrolysis method. Then a p-type CuSCN layer was deposited on this micro-sized n-ZnO to produce a p-n heterojunction. Temperature dependent current-voltage characteristics were measured in the temperature range 150-300 K with a step of 25 K. The current-voltage characteristics exhibit electrical rectification behavior. The zero bias barrier height Φ_b0 increases and the ideality factor n decreases with an increase in temperature. The apparent Richardson constant and mean barrier height were found to be 0.0028 A cm^− 2 K^− 2 and 0.228 eV respectively in the range 150-300 K. After a barrier height inhomogeneity correction, the Richardson constant and the mean barrier height were obtained as 65.20 A cm^− 2 K^− 2 and 0.840 eV, respectively.     

Selective semiconductor sensors for reducing and oxidizing gases

The ever-increasing need for sensors capable of detecting and monitoring toxic and flammable gases is presented and the various techniques available are introduced. Semiconductor devices based on tin dioxide, which potentially have many desirable characteristics, are discussed in detail with particular reference to the work in Swansea which has focused on the problem of selectivity.     

Enhanced triethylamine sensing performance of superfine NiO nanoparticles decoration by two-dimensional hexagonal boron nitride

The novel two-dimensional hexagonal boron nitride (h-BN) decorated nickel oxide (NiO) heterojunction was successfully synthesized by a facile solvothermal precipitation method combining with heat treatment. SEM and TEM analysis were used to corroborate the average size (~8 nm) and overall distribution of superfine NiO nanoparticles on h-BN. XRD, FT-IR and XPS characterization confirmed the configuration of highly crystallinity and p-n heterojunction as well as the presence of surface oxygen vacancy defects. Gas sensing test results revealed that the decoration of h-BN could significantly enhanced triethylamine (TEA) sensing property of NiO. The main contribution of such remarkable results lies in NiO nanoparticles that are close to Debye length scale were embedded on vacancy defects of functionalized h-BN nanosheets, which can optimize sensitivity and selectivity by taming two-dimensional (2D) interfacial electronic effects that strongly affect nonmetal-support interaction between grain boundaries. Meanwhile, the formation of p-n Schottky nanoscale heterojunction between NiO and h-BN can significantly enlarge resistance variation and efficiently promoted the adsorbed triethylamine molecules to oxidize into NO₂, H₂O, and CO₂. Our work highlights the important role of coupling functionalized h-BN in gas sensors, which can also provide a valuable avenue in boosting the sensing performance.     

ZnO thin films for VOC sensing applications

ZnO thin films were prepared by reactive RF sputtering on thermally oxidized Si for gas sensing applications. Three VOC vapors were chosen to investigate the response behavior of the prepared ZnO. Acetone, isopropanol and ethanol were tested, and the sensitivity of the sensor toward acetone was the highest (S ∼ 100) for 500 ppm acetone at 400 °C. The largest sensitivity was achieved at 400 °C for all the above vapors. The sensor shows a stable, reversible and repeatable behavior in the acetone concentration ranging from 15 up to 1000 ppm. The mechanism of the sensing was explained according to the ionosorption model.     

Microwave sintering of ZnO nanopowders and characterization for gas sensing

Thick ?lm gas sensors based on ZnO nanopowders were fabricated by using microwave sintering. The surface and cross section morphologies were characterized by ?eld-emission scanning electron microscopy (FE-SEM). The stability of the microstructure was studied by impedance spectroscopy. The results showed that the shape of the nanoparticles was not changed through microwave sintering, and the thick films had the more dense microstructures than that by muffle oven sintering. The resistance-temperature characteristic and the responses to toluene, methanol and formaldehyde revealed that the microwave sintering technique could effectively control the growth of ZnO nanoparticles, realize the uniform sintering of thick film, gain the stable microstructure and improve the response of sensor. In addition, the formative mechanism of the thick film microstructure was proposed according to microwave sintering mechanism.     

A MEMS toolkit for metal-oxide-based gas sensing systems

Silicon micromachining technologies have been used to develop metal oxide gas sensor elements with very small heating power consumption. With the power consumption of a single micromachined sensor element being an order of magnitude less than that of commercial thick-film devices, novel kinds of gas sensing systems become feasible, which allow higher selectivity, lower drift and built-in self-test functionalities to be realised within the power budget of a single thick-film gas-sensing element. Such systems can be built up using components from an emerging MEMS toolkit for miniaturised gas sensing systems. The article presents components of this toolkit and points out system functionalities that can be achieved by combining elements from this kit.     

Detection mechanisms of smoke compounds on homogenous semiconductor sensor films

The conductivity changes of tin oxide sensor films kept at 270 °C to various organic compounds originating during the combustion of wood were investigated by HRGC/SOMMSA (high resolution gas chromatography/selective odorant measurement by multisensor array). The films show high sensitivity and selectivity to organic compounds with hydroxyl groups. Phenolic structures lead to strong conductivity increases. Exposure to toluene, furfural and acetone does not change the film conductivity. The reaction of the films to beech wood smoke is primarily due to 2-methoxyphenol and 2,6-dimethoxyphenol derivatives with para-substituted alkyl and alkenyl groups, which originate in hardwood lignia. Both types of compounds occur in relatively high concentrations during smouldering and both are sensitively detected. In spruce wood smoke only reactions to 2-methoxyphenol derivatives occur. Reaction mechanisms are discussed in some details.     

Contactless electromodulation and surface photovoltage spectroscopy for the nondestructive, room temperature characterization of wafer-scale III–V semiconductor device structures

This paper will review the use of the contactless methods of photoreflectance, contactless electroreflectance, and surface photovoltage spectroscopy for the nondestructive, room temperature characterization of a wide variety of wafer-scale III–V semiconductor device structures. Some systems that will be discussed include heterojunction bipolar transistors (including determination of collector and emitter doping levels, alloy composition, and dc current gain factor, pseudomorphic GaAlAs/InGaAs/GaAs high electron mobility transistors (including the determination of the composition, width, and two-dimensional electron gas density in the channel), edge emitting lasers [InGaAsP/InP (including the detection of p-dopant interdiffusion), graded index of refraction separate confinement heterostructure GaAlAs/GaAs/InGaAs], and vertical-cavity surface-emitting lasers (determination of fundamental conduction to heavy-hole excitonic transition and cavity mode). These methods are already being used by more than a dozen industries world-wide for the production-line qualification of these device structures.