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。     

退火对电容型硅纳米孔柱阵列湿度传感器性能的影响

基于硅纳米孔柱阵列(Si-NPA)制备电容型湿度传感元件,并在250℃、450℃和550℃三个温度下对元件进行退火处理。测试数据显示,在测试温度低于550℃时,Si-NPA湿敏元件灵敏度随退火温度的升高而增大,但响应时间略微延长,湿滞回差略微增大;550℃退火后,元件的灵敏度急剧降低。采用场发射扫描电镜(FE-SEM)对不同温度退火的硅纳米孔柱阵列表面形貌进行观察,发现550℃退火元件的微观多孔结构发生了明显变化,即多孔结构致密化。结果表明,通过合适温度退火可以显著提高Si-NPA湿敏元件灵敏度,同时仍然保持较快的响应速度和较小的湿滞回差。     

氧化锌纳米棒/单晶硅的酒精传感器研究

首先采用射频溅射在单晶硅(Si)上制备氧化锌(ZnO)薄膜,作为生长ZnO纳米棒的晶种层,再在水热条件下生长ZnO纳米棒.X射线衍射、X射线能量色散谱,扫描电镜及室温光致发光谱对样品的物相结构、成分、表面微观形貌和晶体缺陷进行了表征.结果表明合成的ZnO纳米棒是六方纤锌矿结构,长径比较高,结晶良好.研究了ZnO纳米棒/单晶Si传感器在空气和酒精气体中的电压-电流(Ⅰ-Ⅴ)特性,阻抗谱及响应-恢复时间.该传感器在+6 V的偏置电压下,其电阻在0.08 g/L酒精气体中下降71%,响应时间小于1 min,可以作为一种新型的酒精气体传感器.     

WO_3/Si-NPA复合薄膜的电容湿度传感性能研究

制备了基于硅纳米孔柱阵列(Si-NPA)的WO3/Si-NPA复合薄膜,并对其表面形貌进行了表征,研究了其电容湿度传感性能和基点电容的温度漂移。研究表明:WO3/Si-NPA继承了衬底Si-NPA规则的阵列结构的表面形貌特征,WO3的沉积形成了连续的WO3薄膜,WO3/Si-NPA是一种典型的纳米复合薄膜。室温下,WO3/Si-NPA的电容值随测试频率的增加而单调减小,但其灵敏度则在100 Hz时达到最大值。在此测试频率下,当环境的相对湿度从11%RH增加到95%RH时,元件的电容增量高达16 000%,显示WO3/Si-NPA对环境湿度有较高的灵敏度。同时,电容的湿度响应曲线显示出很好的线性。对其基点电容的温度稳定性研究表明:WO3/Si-NPA用作湿度传感的最佳工作温度区为15~50℃。     

粗糙表面的可控润湿性研究*

本文利用微机械加工技术,通过改变材料表面微观几何结构,研究材料表面微结构对于表观润湿性的影响规律.我们在以前工作的基础上,分别研究了不同设计尺寸的表面微柱阵列结构的亲水表面的表观接触角的变化,研究结果表明,通过改变材料表面的微结构,在亲水的本征表面上,粗糙表面的表观接触角更加符合Wenzel的理论预测.文章也通过在微柱表面利用化学腐蚀方法制作多孔硅结构的方法,形成了具有阶层结构的粗糙表面.具有多孔硅结构和微柱阵列的疏水表面(OTS)上,测得最大接触角是157.18°.     

纳米碳化硅/硅纳米孔柱阵列湿敏性能研究

以硅纳米孔阵列(Si-NPA)为衬底,采用化学气相沉积法分别制备了SiC纳米颗粒/Si-NPA(nc-SiC/Si-NPA)和SiC纳米线/Si-NPA(nw-Si/Si-NPA)复合体系,并对其表面成分和形貌、室温湿敏性能进行了表征.实验结果表明,nc-SiC/Si-NPA和nw-SiC/Si-NPA均对水蒸气表现出...     

一种新型三维敏感气体传感器的研究

在平面微电极式结构的基础上,提出了一种新型薄膜气体传感器,其主要结构引用了离散阵列的概念,将传统的长方体型薄膜改进为由多条小长方体有间隔的并行排列的离散结构,使敏感薄膜具有了三维敏感效应。根据半导体气敏薄膜的扩散响应理论,对传感器的响应时间和灵敏度特性进行了理论分析,证明新型传感器具有响应时间更短、灵敏度更高的优点;并分析了薄膜厚度对传感器响应时间的影响。     

DC-60 GHz硅基垂直互联结构仿真设计

设计了一种基于多层硅转接板堆叠的垂直互联结构,对DC-60 GHz频段内不考虑和考虑硅表面SiO2层的两种层间结构的垂直互联仿真结果进行对比,证明了硅表面SiO2层存在会对谐振频率及阻抗等射频性能产生影响;对后者垂直互联结构进行参数优化,射频传输性能较好,频率40 GHz以下时回波损耗S11小于-30 dB,60 GHz以下整体S11小于-15 dB,插入损耗S12在50 GHz以下大于-0.32 dB;研究了硅表面SiO2绝缘层厚度变化对射频信号传输性能的影响,结果表明适当增加其厚度有助于垂直互联结构性能优化.     

多晶硅湿敏元件的研究

用外延生长法,在具有二氧化硅层的单晶硅衬底上外延生长一层多晶硅,采用平面工艺在其上形成具有数千个矩形小孔的精密阵列,构成多晶硅阵列式湿敏元件.对元件的特性进行了研究,其吸湿响应时间为280ms,脱湿响应时间为620ms.在理论上,引入两种水分子与阵列作用机制,其一,水分子与多晶硅晶界的作用;其二,水分子与阵列结构的碰撞作用.由此计算了元件阻值随相对湿度变化的关系为R=R_0(1-Ax%)/(1+Dx%)将理论值与实验值进行比较, 两者吻合较好.     

介孔SnO2气敏性能研究

为了改善传感器的气敏性能,采用溶胶-凝胶法合成了介孔SnO2,并研究了其气敏性能.研究表明:与纳米SnO2相比,介孔SnO2气体传感器具有较高的酒精、二甲苯响应,在100～150℃对甲醛的响应也大大提升.在100～ 150℃,干扰气体为甲苯和二甲苯时,介孔SnO2表现远远优越于纳米SnO2的酒精选择性.在100,150,350℃,干扰气体为甲苯时,介孔SnO2也具有优越的甲醛选择性.介孔SnO2的响应时间较短,但恢复时间较长.     

Structural and capacitive humidity sensing properties of nanocrystal magnetite/silicon nanoporous pillar array

A composite thin film was fabricated by coating nanocrystal magnetite (nc-Fe₃O₄) on silicon nanoporous pillar array (Si-NPA), which shows a regular hierarchical structure composed by the pillar array in micron dimension and the nanoporous structure in the film of Fe₃O₄. Capacitive humidity sensors were made based on nc-Fe₃O₄/Si-NPA and the corresponding sensing properties were investigated. The experimental results disclosed that nc-Fe₃O₄/Si-NPA sensor exhibits high sensitivity, strong output signal intensity, and short response times. These high performances of nc-Fe₃O₄/Si-NPA sensor are explained on the basis of the structural and compositional factors of nc-Fe₃O₄/Si-NPA.     

基于Si-NPA的BaTiO3薄膜的电容湿敏性能研究

采用溶胶-凝胶和旋涂技术制备了基于Si-NPA的BaTiO3薄膜(BaTiO3/Si-NPA).场发射扫描电镜和X射线衍射实验表明,钙钛矿结构BaTiO3薄膜很好地覆盖了Si-NPA表面.通过蒸镀双面梳状电极,制作了电容型BaTiO3/Si-NPA湿敏元件并对其湿敏性能进行了测试.结果表明,室温下湿敏元件在11%～95%RH范围内具有很高的灵敏度和较快的响应速度,且电容值的对数对湿度呈现出很好的线性.虽然该薄膜湿敏元件在不同湿度下均存在温度漂移,但分析表明这种漂移有可能通过电极设计或信号补偿加以解决.     

High sensitivity ethanol gas sensor integrated with a solid-state heater and thermal isolation improvement structure for legal drink-drive limit detecting

The paper reports the successful fabrication of ethanol gas sensors with tin-dioxide (SnO₂) thin films integrated with a solid-state heater, which is realized with technologies of micro-electro-mechanical systems (MEMS), and are compatible with VLSI processes. The main sensing part with dimensions of 450×400 μm² in this developed device is composed of a sensing SnO₂ film, which is fabricated by electron-gun evaporation with proper annealing in ambient oxygen gas to yield fine particles and good structure. An integrated solid-state heater with a 4.5 μm-thick cantilever bridge (1000×500 μm²) structure is made of silicon carbide (SiC) material by MEMS technologies. The sensitivity for 1000 ppm ethanol gas reaches as high as 90 with 10 s and 2 min for the response and recovery time, respectively, at an operating temperature of 300°C. Those experimental results also exhibit a much superior performance to that of a popular commercial ethanol gas sensor TGS-822. Therefore, the developed sensor with high performance is a good candidate for some specific application in automobile to detect drink-drive limit and allows an array integration available with various films for controlling each element at separate resistance.     

Numerical simulation for sensitivity and accuracy enhancement of micro cantilever-based biosensor employing truss structure

Micro-cantilevers are very effective and reliable devices for bio-sensing applications. In this work, a novel biosensor based on micro-cantilever array was designed, simulated and optimized for different bio-sensing applications with high sensitivity, high accuracy, high throughput, and high Q factor. A truss structure designed in the anchored end of the micro-cantilever which was effective in improving the sensitivity to increase detection accuracy. Also, the effects of the surrounding medium are minimized by this structure to achieve high Q factor and longer vibration for bio-sensor. All the results are compared by the conventional micro-cantilever. As a result, the Q factor is increased from 52.1 to 126.1 within water medium and from 51.8 to 120 within ethanol medium. The actuation of novel MCL is simulated by different piezoelectric materials, the results proof that the amplitude of displacement for the PZT-5H is more efficient than AlN.

     

Experimental and numerical investigation of capillary flow in SU8 and PDMS microchannels with integrated pillars

Microfluidic channels with integrated pillars are fabricated on SU8 and PDMS substrates to understand the capillary flow. Microscope in conjunction with high-speed camera is used to capture the meniscus front movement through these channels for ethanol and isopropyl alcohol, respectively. In parallel, numerical simulations are conducted, using volume of fluid method, to predict the capillary flow through the microchannels with different pillar diameter to height ratio, ranging from 2.19 to 8.75 and pillar diameter to pitch ratio, ranging from 1.44 to 2.6. The pillar size (diameter, pitch and height) and the physical properties of the fluid (surface tension and viscosity) are found to have significant influence on the capillary phenomena in the microchannel. The meniscus displacement is non-uniform due to the presence of pillars and the non-uniformity in meniscus displacement is observed to increase with decrease in pitch to diameter ratio. The surface area to volume ratio is observed to play major roles in the velocity of the capillary meniscus of the devices. The filling speed is observed to change more dramatically under different pillar heights upto 120 μm and the change is slow with further increase in the pillar height. The details pertaining to the fluid distribution (meniscus front shapes) are obtained from the numerical results as well as from experiments. Numerical predictions for meniscus front shapes agree well with the experimental observations for both SU8 and PDMS microchannels. It is observed that the filling time obtained experimentally matches very well with the simulated filling time. The presence of pillars creates uniform meniscus front in the microchannel for both ethanol and isopropyl alcohol. Generalized plots in terms of dimensionless variables are also presented to predict the performance parameters for the design of these microfluidic devices. The flow is observed to have a very low Capillary number, which signifies the relative importance of surface tension to viscous effects in the present study.     

低阻TiO_2基三甲胺气体传感器性能分析

按旁热式结构采用以TiO2为基质对InSb2O3Nb2O5氧化物不同的重量比去掺杂研制成的三甲胺(TMA)气体传感器,大幅度降低了加热功率和其在空气中的阻值,器件对响应TMA气体具有灵敏度高、响应时间快、恢复时间短、长期稳定等特点,对干扰气体NH3具有良好的选择性。