Five-contact silicon structure based integrated 3D Hall sensor

A new silicon integrated 3D Hall sensor for high-accuracy magnetic field measurements is suggested and tested. Its unique device design in having only five n/sup +/ contacts allows simultaneous and independent obtaining of the full information about the three components of the magnetic field vector. The device is manufactured through a simple planar process and requires the use of four masks. The lateral dimensions of the sensor are 270/spl times/270 /spl mu/m; the channel magnetosensitivities are S/sub x/=S/sub y/=85 V/AT and S/sub z/=29 V/AT; the nonlinearity and channel cross-sensitivities at B/spl les/1 reach no more than 0.6% and 3-4%, respectively; and the frequency response to AC magnetic field is greater than 30 kHz     

制备条件对TiO2薄膜结构和光学性能的影响

借调节sol-gel法中溶胶的pH值,薄膜的热处理温度,研究了它们对TiO2薄膜的晶相组成、晶粒大小、表面结构和紫外及可见光吸收性能的影响。结果表明:pH为7时有利于TiO2由锐钛矿向金红石相转变,薄膜的孔隙度为94nm,有较高的表面粗糙度。pH值升高,TiO2薄膜的孔隙度和颗粒度增大;热处理温度升高,薄膜的紫外吸收发生红移,可见光波段透射率降低,故最佳热处理温度为500℃。     

Micro-opto-mechanical vibration sensor integrated on silicon

A new micro-optical vibration sensor has been achieved by combining “integrated optics” and “micromachining” on silicon technologies. The high sensitivity and the wide frequency range have been obtained by using a multimode section in the optical detection circuit. Three prototypes have been installed successfully in an industrial hydroelectric power plant     

MEMS magnetic field sensor based on silicon bridge structure

A MEMS piezoresistive magnetic field sensor based on a silicon bridge structure has been simulated and tested.The sensor consists of a silicon sensitivity diaphragm embedded with a piezoresistive Wheatstone bridge,and a ferromagnetic magnet adhered to the sensitivity diaphragm.When the sensor is subjected to an external magnetic field, the magnetic force bends the silicon sensitivity diaphragm,producing stress and resistors change of the Wheatstone bridge and the output voltage of the sensor.Good agreeme...     

基于硅桥结构的MEMS磁场传感器

提出了一种基于硅桥结构的MEMS磁场传感器结构。其结构由制作在硅桥敏感膜表面的惠斯通电桥和在膜中间沾上铁磁体制成。当传感器处于磁场中时,铁磁体在外磁场中磁化产生磁力,磁力会使硅敏感膜弯曲从而引起压阻改变进而使惠斯通电桥产生电压输出以达到测量磁场的目的。文章通过有限元软件仿真对铁磁体的尺寸进行了优化。实验结果和理论结果较接近。实验测得该传感器最大灵敏度为48mV/T,分辨率为160μT,该传感器可以用来进行强磁场的测量。实验结果结果表明:传感器的重复性和动态响应时间分别约为0.66%和150ms。     

A gas pressure sensor based on ZrO2 thin films for use at high temperatures

A gas pressure sensing device based on ZrO₂ thin films for use at high temperatures is presented. The films were deposited on glass substrates through electron beam evaporation of ZrO₂ tablets in vacuum with residual oxygen pressure of the order of 10^?4 mbar. The piezoresistive characteristics of the device for different pressures of N₂, CO₂, Ar and He at different temperatures were investigated. The experimental results and the underlying physical mechanisms are discussed.     

响应三甲胺气体低阻TiO_2基气体传感器研制(英文)

二氧化钛是一种良好的响应三甲胺气体的敏感材料,然而用它做成传感器后存在一个明显的缺点:阻值太高。文中采用不同气氛热退火和掺杂方法来提高TiO2基材料的电导率,从而制成一种新型低阻敏感元件,对三甲胺灵敏度高、选择性好。     

A potential gas sensor device based on Pd/RGO/TiO2 nanotube ternary hybrid junction

In the present work, fabrication, characterizations and gas sensing performance of a novel ternary hybrid junction device consisting of Pd nanoparticles, Reduced Graphene Oxide (RGO) and TiO₂ nanotubes (NTs) is reported. Electrochemically derived TiO₂ nanotubes were covered partially by RGO matrix in the form of distributed islands, on top of which Pd nanoparticles were dispersed uniformly. After detailed structural and morphological characterizations, gas sensing potentiality of the developed ternary hybrid device was tested for detection of methanol vapor and the sensing performance was compared with that of the RGO-TiO₂ binary structure to ensure the improvement caused by incorporation of the ternary element (Pd). Underlying mechanistic framework for gas sensing, by such ternary junction, was explained with the help of corresponding energy band diagram.     

Response time and mechanism of Pd modified TiO2 gas sensor

In this work, gas response properties of Pd modified TiO₂ sensing films are discussed when exposed to H₂ and O₂. TiO₂ films are surface modified in PdCl₂-containing solution by the dipping method and treated for different treatment times to get different surface states. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Kröger–Vink defect theory are used to characterize the sensing films. The gas response properties indicate that the sensor response time which related to the rate of change of sensor resistance is affected by the activation energy (E). In particular, the sensor treated at 900 °C for 2 h exhibits a response time of about 20–240 ms when exposed to H₂ and 40–130 ms when exposed to O₂ at 500–800 °C.     

TiO2薄膜的相结构调控与表征

本文利用脉冲激光沉积技术在LaAlO3(001)衬底上生长了单晶锐钛矿和双相TiO2薄膜,并利用X射线衍射和透射电子显微术对薄膜的显微结构进行了系统表征.单晶锐钛矿薄膜在LaAlO3(001)衬底上实现了外延生长,双相TiO2薄膜以单晶锐钛矿TiO2为基体,在其中夹杂着金红石TiO2颗粒.TiO2薄膜的相结构可通过调整...     

Effects of surface passivation in porous silicon as H2 gas sensor

This paper investigates the effects of surface passivation in porous silicon (PS) as a hydrogen gas sensor. Two types of sample have been prepared, one with typical HF anodizing solution and the other with the presence of peroxide (H₂O₂) in the solution. The Fourier transform infrared (FT-IR) measurements on the PS layer on the Si substrate showed that the typical PS surface is characterized by chemical species like Si–H and Si–O. Samples anodized with peroxide based (H₂O₂) solution showed a PS structure with higher porosity (～80%) and better surface passivation (higher concentration of Si–O and Si–H species) compared to those not treated with peroxide. Peroxide based PS sample fabricated as an H₂ gas sensor showed better electrical (I–V) sensitivity compared to those without peroxide, which has been associated with good surface passivation. Surface passivation in peroxide based PS is also maintained at higher temperatures (100 °C).     

TiO_2/ACF复合材料降解甲醛的实验研究

以具有很强吸附能力的活性炭纤维(ACF)为载体,将TiO2负载于ACF制成TiO2/ACF复合材料。实验研究TiO2/ACF材料表面甲醛的降解特性。结果表明,ACF表面TiO2的负载量影响甲醛的吸附及光催化降解效果,负载量增加,ACF对甲醛吸附量减小,甲醛的降解率呈先提高后减小趋势。甲醛初始浓度增加,甲醛的降解率减小;光强增加,甲醛的降解率增加;随着相对湿度的增加,甲醛的降解率先增加后减小,当相对湿度为43%时甲醛的降解率最大。     

A low power MEMS gas sensor based on nanocrystalline ZnO thin films for sensing methane

Nanocrystalline ZnO based sensor using micromachined silicon substrate has been reported for efficient detection of methane as opposed to conventional SnO₂ based micromachined sensors for its higher compatibility to silicon IC technology and greater response. A suitably designed nickel microheater has been fabricated on to the micromachined Si platform. The optimum temperature for highest response magnitude and lowest response time were found to be 250 °C although relatively high (76.6%) response is obtained even at as low as 150 °C. Our study showed quite high response magnitude (87.3%), appreciably fast response time (8.3 s) and recovery time (17.8 s) to 1.0% methane at 250 °C. The sensor showed appreciably fast response (14.3 s) and recovery time (28.7 s) at 150 °C. The power consumption at an operating temperature of 250 °C was 120 mW and at 150 °C is only ～70 mW. Moreover, this type of sensor was found to give fairly appreciable response for lower methane concentrations (0.01%) also. For higher methane concentrations (>0.5%) response is detectable even at 100 °C where the power consumption is only ～40 mW.     

Properties of TiO2 films on silicon substrate

Influence of the substrate material and the effect of oxygen plasma on the microprofile and electrical properties of TiO₂ films deposited by radio-frequency magnetron sputtering are studied. It is shown that the most continuous films with the smallest roughness are obtained when deposited onto silicon substrates. The change in the capacitance-voltage and conductance-voltage characteristics of the structures upon their exposure to oxygen plasma is accounted for by the diffusion of oxygen atoms across the titanium-dioxide film and by the appearance of a SiO₂ layer at the Si-TiO₂ interface.     

石英基多层纳米TiO2-FeOOH复合材料的制备和 显微结构的表征

以石英玻璃片为基底,利用自组装技术在TiCl4-HCl体系中生长纳米TiO2,与在Fe(NO3)3-HNO3体系中生长纳米FeOOH制备负载型多层不同层序FeOOH-TiO2纳米复合薄膜光催化材料.高分辨透射电镜(HRTEM)表征结果显示:复合膜由纳米锐钛矿和针铁矿构成.UV-Vis表征结果显示:TiO2与FeOOH间的复合使TiO2吸收带均发生一定程度的红移,其中FeOOH/TiO2/FeOOH/TiO2和FeOOH/TiO2/FeOOH复合薄膜的吸收带分别为490 nm和498 nm;在以罗丹明B溶液为模拟废水的光催化实验中发现:负载FeOOH/TiO2/FeOOH/TiO2和FeOOH/TiO2/FeOOH的两种复合薄膜材料的光催化效果最佳;并且FeOOH膜在复合膜最外层比TiO2膜在最外层时光解效率高.具有一定吸附能力的针铁矿薄膜与TiO2薄膜的复合优化了复合膜内部微孔结构,促进两者间形成了积极地吸附-光催化耦合增强效应.     

Charge-transport mechanisms in heterostructures based on TiO2:Cr2O3 thin films

n-TiO₂:Cr₂O₃/p-Si anisotype heterostructures are fabricated by the deposition of a TiO₂: Cr₂O₃ film by electron-beam evaporation onto a polished polycrystalline silicon substrate. Their electrical properties are studied and the dominant charge-transport mechanisms are determined: multistage tunneling-recombination mechanism involving surface states at the TiO₂: Cr₂O₃/Si metallurgical interface under small forward biases and tunneling at biases exceeding 0.8 V. The reverse currents through the heterostructures under study are analyzed in terms of the single-stage tunneling mechanism of charge transport.     

Refractive index and temperature optical fiber sensor based on thin core S-taper and spherical structure

A Mach-Zehnder interferometer (MZI) for simultaneously measuring refractive index (RI) and temperature is proposed and verified in this paper. The sensor head is composed of thin core fiber (TCF) S-taper structure and spherical structure. By monitoring two interference dips, experimental results show that the RI sensitivities are ?70.392 nm/RIU and ?60.08 nm/RIU in the RI range of 1.338 4—1.350 0, respectively. And the temperature sensitivities are 0.050 72 nm/°C and 0.071 7 nm/°C in the temperature range of 30—70 °C, respectively. The simultaneous measurement of the temperature and external RI is demonstrated based on the sensitive matrix. The sensor also has the advantages of low cost, simple structure and high sensitivity.     

射频反应磁控溅射掺杂MWCNTs的SnO2薄膜NO2气敏传感器的研究

采用射频反应磁控溅射方法制备了氧化锡/多壁碳纳米管（SnO2/MWCNTs）薄膜材料,并在此基础上研制NO2气敏传感器。采用X射线衍射仪（XRD）、X光电子能谱仪（XPS）、扫描电子显微镜（SEM）来研究WO3/MWCNTs材料的表面形貌、表面化学状态、表面化学元素等材料特性,研究结果表明MWCNTs已经掺杂进SnO2材料,合成的SnO2/MWCNTs气敏传感器表现出对低浓度（甚至低于10ppb）的NO2气体有较高的灵敏度和较好的反应-恢复特性,并解释了该传感器的工作机理是基于pn结（P型MWCNTs和N型SnO2)作用的结果。     

An MWCNT-doped SnO_2 thin film NO_2 gas sensor by RF reactive magnetron sputtering

An MWCNT-doped (multi-walled carbon nanotube) SnO_2 thin film NO_2 gas sensor, prepared by radio frequency reactive magnetron sputtering, showed a high sensitivity to ultra-low concentrations of NO_2 in the parts per billion range. X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy (SEM) characterizations indicated that the MWCNTs were affected by the morphology of the SnO_2 thin film and the particle size.The properties of the MWCNT-doped SnO_2 sensor, such as sensitivity, selectivity, and response-recovery time, were investigated. Experimental results revealed that the MWCNT-doped SnO_2 thin film sensor response to NO_2 gas depended on the operating temperature, NO_2 gas concentration, thermal treatment conditions, film thickness, and so on.The mechanism of the gas-sensing property of the MWCNT-doped SnO_2 thin film sensor was investigated and showed that the improved gas-sensing performance should be attributed to the effects between MWCNTs (p-type) and SnO_2 (n-type) semiconductors.     

Mechanism of formation of the response of a hydrogen gas sensor based on a silicon MOS diode

Experimental data on the dependence of the flat-band voltage and relaxation time for the capacitance of the space-charge region in an MOS diode (Pd-SiO₂-n-Si) on the hydrogen concentration in a hydrogen/air gaseous mixture are discussed. It is assumed that variation in the flat-band voltage U _fb in an MOS structure with the thickness d = 369 nm subjected to a hydrogen/air gaseous mixture can be accounted for by the formation of dipoles in the Pd-SiO₂ gap due to polarization of hydrogen atoms (H _a ). An analytical expression describing the dependence of variation in the flat-band voltage ΔU _fb on the hydrogen concentration \(n_{H_2 } \) was derived. In MOS structures with d ≤ 4 nm (or MOS diodes), the value of ΔU _fb is mainly controlled by passivation of the centers responsible for the presence of the surface acceptor-type centers at the SiO₂-n-Si interface by hydrogen atoms. Analytical expressions describing the dependences of ΔU _fb and the capacitance relaxation time in the space-charge region on \(n_{H_2 } \) are derived. The values of the density of adsorption centers and the adsorption heat for hydrogen atoms at the Pd-SiO₂ and SiO₂-n-Si interfaces are found.