bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Study on the Side-Opening Filling Process at the Interface between Microchannels with Different Widths
Authors: Xie Fei , Wang Yun Shan , Wang Wei , Wu Wen Gang , Li Zhi Hong , Yossifon Gilad , Chang Hsueh Chia
Published: July 2011

Micro/nanochannel is of great importance due to its wide applications in micro total analysis system. In a given micro/nanofluidic device, the nanochannel and microchannel can works as function provider and reagent delivering passage, respectively. The easiest way to fabricate micro/nanochannel is depositing material onto a predefined microchannel until nanometer-sized pattern is obtained. Although the deposition process inside the microchannel has been studied before, the filling performance at the side-opening, the connection between microchannels with different widths, is limited studied. The different filling performance at side-opening will lead to a distinct geometrical size. In this work, side-opening filling process during a low pressure chemical vapor deposition of silicon dioxide onto pre-etched microchannels with patterns of straight, triangle and rhombus shapes was preliminarily studied. A filling factor was defined to describe the side-opening filling performance. The present results indicated that the side-opening filling will be affected by the side-opening width, the depth of the microchannel and the microchannel shape.
Simulation and Experimental Study of a Porous Electroosmotic Pump
Authors: Ling Zhou , Yang Tao , Meng Fan Chao , Yi Lin , Zhang Xiang Xian
Published: July 2011

Aiming at the coupling problems of electrical field and flow field in porous media microchannels, the mathematical model of electroosmotic(EO) flow is built. For a single microchannel, the influence of voltage on velocity and joule heat is analyzed by using CoventorWare. Numerical analysis shows that the velocity is proportional to the voltage and the joule heat is small and negligible. For the porous media, the flow rate is investigated by truncated Gaussian distribution of pore diameter. The electroosmotic microporous pump is fabricated, and the experimental results indicate that the maximum flow rate of porous media micropump is 16.89ml/min and the maximum pressure is 120.1kPa.
Experimental Investigations of Anode Structure on the Performance of Air-Breathing µDMFC
Authors: Yuan Zhen Yu , Zhang Shu Bin , Leng Jia Xing , Zhang Yu Feng , Liu Xiao Wei
Published: July 2011

In this paper, silicon-based micro direct methanol fuel cells (µDMFCs) with different anode structures were designed and investigated experimentally, the current collectors were fabricated using micro-electromechanical system (MEMS) technology. a novel encapsulation method was also designed using PDMS. The study of the effect of different anode flow fields suggested that the serpentine flow field has the optimal performance. The experimental results also revealed that an open ratio of around 47% led to the best cell performance, a maximum of power density of 13.2 mW/cm2 was achieved with 1.0 M methanol solution.
Development of a Novel Electrochemical Surface Plasmon Resonance Instrument Based on a Mini Three Electrode Flow Cell
Authors: Zhang Lu Lu , Cui Da Fu , Chen Xing , Cai Hao Yuan , Li Hui , Sun Jian Hai
Published: July 2011

The construction and performance of a novel electrochemical (EC) surface plasmon resonance (SPR) instrument based on a mini three electrode flow cell that was designed and manufactured by MEMS technology is described. The working electrode is 50nm gold and counter and reference electrodes, made of Au and Ag/AgCl separately, are 0.6 mm in diameter. The flow channel is made of polydimethylsiloxane (PDMS) with 1mm in width, 200μm in depth, 5μL in volume. The process for activating and modifying the working electrode is given by the real-time SPR detection. The Cyclic voltammetry (CV) and SPR detection are conducted simultaneously in potassium ferricyanide solution system. It is proved that the signal of redox reaction and the change of refractive index have a well correlation by the potential sweep experiment. Four kinds of concentration of potassium ferricyanide are analyzed and the peak oxidizing current, obtained from the curve, is proportional to the respective concentration of the sample. The EC-SPR experiment is also carried out in CuSO4 system and the results is similar to potassium ferricyanide.
Study of Under Etching Characters of Si (100) in Surfactant Added TMAH
Authors: Hu Qi Fang , Gao Cheng Chen , Hao Yi Long , Zhang Yang Xi
Published: July 2011

This work focuses on the etching characteristic of (100) silicon wafer in surfactant added tetramethyl-ammonium-hydroxide (TMAH:( CH3)4NOH) solution. The experimental result shows that under etching effect in TMAH achieves a significant reduction by adding fatty alcohol ethoxylate (R-O (CH2-CH2)n-OH) in the solution. Synperonic-A series fatty-alcohol-ethoxylate with increasing length of ethylene oxide segments are used to carry out the experiment. Comparing with the pure TMAH, the maximum under etching rate in the surfactant added TMAH is reduced to three quarters. The etching loss of convex corners is negligible for shallow to medium-deep etching (<30μm).
The Fabrication and Experiment of a Four-Electrode Conductivity Sensor for Fresh Water
Authors: Li Wei , Liu Fu Yong , Wang Ke Yuan , Wen Zhi Yu
Published: July 2011

In this paper, a new four-electrode sensor for fresh water conductivity measurements is presented.The measurement system includes two parts: a four-electrode conductivity sensor unit and an integrated measuring circuit. The distribution of a four-electrode in electric field and the size of four electrodes are simulated by ANSYS - the MEMS simulation tool. The prototype of the conductivity sensor, with a four-electrode (each electrode is measuring 6mm×2mm or smaller), was fabricated on a PCB. The conductivity of a tested sample could be obtained according to output of the amplifier by calibrating the voltage of the conductivity of the standard liquid. The voltages of the conductivities, in the range from 0.34V to 9.00V, are detected by an oscillograph. This test result proves that it is promising to measure conductivity of fresh water utilizing the sensor based on the four-electrode system.
Fabrication of PDMS Microchannels with Round Profiles Using Glycerol Molds
Authors: Du Min , Zhao Hang Bo , Ye Xiong Ying , Zhou Zhao Ying
Published: July 2011

Poly(dimethylsiloxane) (PDMS) based soft lithography has been widely used to make microfluidic devices, while the cross-sections of the microchannels using the solid molds are mostly rectangle. We present a method for fabricating PDMS channels with a round profile, which utilizes hydrophilic/hydrophobic modification of substrates and glycerol molds. The glycerol mold was formed by letting glycerol stay on the patterned hydrophilic area surrounded by hydrophobic area. The different aspect ratios of the profiles were realized using different hydrophilic/hydrophobic modifications with small channel widths. The round profile channels with 10%-30% aspect ratios were obtained.
Rapid Microfluidc Biochips Fabrication by Femtosecond Laser on Glass Substrate
Authors: Chang Chin Lung , Ju Weij Hong , Liou Ching Liang , Leong Jik Chang , Fu Lung Ming
Published: July 2011

This paper uses a femtosecond laser scriber to perform the direct-writing ablation of glass substrate for the development of microfluidic biochips. The surface quality of the ablated microchannels was examined by scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurement techniques. The developed femtosecond laser ablation system provides a versatile and economic approach for the fabrication of glass-base microfluidic chips. In the laser writing process, the desired microfluidic patterns are designed using commercial computer software and are then transferred to the laser scriber to ablate the trenches. The results show that a very smooth channel wall can be achieved through the annealing process at the temperature 650°C and 5 hours. The system provides an economic and powerful means of rapid glass microfluidic biochips development.
Rapid Detection of Methanol in an Integration Microfluidic Chip
Authors: Wang Yao Nan , Liou Ching Liang , Wu Ming Chang , Tsai Chien Hsiung , Fu Lung Ming
Published: July 2011

A rapid and simple technique was developed for detecting methanol with very small amount of sample by using PMMA (Polymethyl-Methacrylate) microfluidic chip, which fabricated by a commercially available CO2 laser scriber. The experimental results indicate that linearity expression R2 can approximate 0.936 using the proposed integrating microfluidic chip when the 2 unit methanol oxidase (MOX) and basic fuchsin to detect methanol. Hence, the current device provides a valuable tool for rapid methanol detection, while its micro mixer system delivers a simple yet effective solution for mixing problems in the micro-total-analysis -systems field.
A Tire Pressure Monitoring System Based on MEMS Sensor
Authors: Zhang Jian , Zhang Zhao Hua , Chen Tao , Kong Xiang Ming , Ren Tian Ling , Liu Li Tian
Published: July 2011

TPMS (Tire Pressure Monitoring System) has played a more and more significant role in safely driving nowadays. Low power consumption and excellent accuracy are two of the most important parameters. In this paper, a TPMS with driving status judgment and low-power measurement is designed and realized. A vibration switch is applied to judge the different status of running and stopping. Based on the judgment of driving status, pressure and temperature, different operations will be carried out in order to achieve lower power consumption. The whole system is working intermittently. It has a good performance with a theoretical lifespan of 2 years. The tested communication distance is more than 30m and the resolution is better than 4KPa. A MEMS pressure sensor using SOI wafer with high consistency and accuracy for this TPMS is designed and fabricated. Deep trench etching is adopted to make pressure reference cavity. The ratio of sensitivity variance to its average is 3.5%, which illustrates a good consistency. The total accuracy of the sensor is better than 0.3% and the nonlinearity is less than 0.2%.
Polarization-Noise in Integrated Optical Gyro
Authors: Meng Zhao Kui , Jiao Zhi Chao , Liu Hui Lan , Feng Li Shuang , Li Ru Ya
Published: July 2011

Resonator Integrated Optic Gyro (R-IOG) adopts advantages of the micro integrated optoelectronic technique, whose ring resonator is fabricated by optical integrated circuit. Polarization fluctuation induced noise is one of the dominant noise sources in resonator. State of polarization (SOP) of the input light, polarization maintaining quality of the coupler and the waveguide and the fluctuation of the temperature are main parameters which affect polarization noise of integrated optical gyro. Through simulations and experiments, three countermeasures are introduced. The first and second are for exciting one polarization mode of the waveguide. The first way is modulating the SOP of the input light utilizing polarization controller or polarizer and the second one is raising polarization maintaining quality of the waveguide through the birefringence caused by residual stress and core size. The third way is increasing the distance of two resonance dips by control the temperature at an appropriate point to fix one resonance dip at the center of the other resonance interval. The polarization noise can be suppressed through the ways mentioned above.
A Piezoelectrically Actuated Scaning Micromirror Integrated with Angle Sensors
Authors: Qian Rong Rong , Wen Zhi Yu , Chen Li
Published: July 2011

A novel piezoelectrically actuated scanning micromirror integrated with angle sensors is presented. The mirror with large size of 3×3mm2 locates in the center of the device, and piezoelectric actuators are symmetrically placed on both sides of the mirror. They are connected through torsion bars in which piezoelectric angle sensors are integrated. In order to obtain large deflection angle at a low operation voltage, the new actuator consisting of several parallel piezoelectric cantilevers is adopted. The machematical models of the mirror and piezoelectric actuator are given, and the piezoelectric angle sensors are designed to obtain high sensitivities. The simulation results indicate that the maximum mechanical deflection angle of the micromirror is 12.4° at an operation voltage of 25V, and the maximum output voltage of the angle sensor is 164.3mV. The resonant frequency associated with the torsional mode is 960Hz. The sensitivity of the angle sensor is 13.3mV/° without amplifying. The Scanning miromirror is suitable for optical scanning systems such as the microscope, the micro-spectrometer, the medical imaging, the barcode reader and so on.
A Miniaturized Spectrometer Based on Optical Modulator Composed of Grating and Tunable Fabry-Perot
Authors: Wei Nai Ke , Ni Zhu Gao , Yao Jun , Zhu Jian Hua , Gao Fu Hua
Published: July 2011

In this paper an innovative miniaturized spectrometer has been presented. The structure is similar to a grating spectrometer, but its optical modulator is composed of a grating and a tunable Fabry-Perot (FP). The collimated light is diffracted by the grating and filtered by the FP, and interference fringes distribute separately on the focal plane. The position of fringes moves when the FP is tuned, this helps in the scanning and detecting of the peak wavelength of fringes. The principle and characteristics of the spectrometer are discussed in detail.
Design and Test of MEMS Attitude Measurement Unit for Fall Detection
Authors: Liu Xiao Yan , Zhou Zhao Ying , Xiong Wei
Published: July 2011

Fall is a risky event in the elderly people’s daily life, it often cause serious injury both in physiology and psychology. A MEMS attitude measurement system is designed for fall detection in real time. This paper presents the design and error test of the attitude measurement unit. Each unit contains orthogonally mounted triads of accelerometers, magnetometers and gyros. With an integrated microcontroller for attitude calculating and flash for data storage, the size of the unit is 32mm×23mm×12mm. An extended Kalman filter based on quaternions is designed for attitude measurement. The digital angle output rate is 100Hz. A new method based on coordinate transformation for attitude measurement error test is introduced, using a single axis turntable and a fixed angle wedge. Theory of the testing method is presented and test experiments are performed. Test results show that attitude measurement error is less than 2°, which meets the requirement of fall detection precision. The fall detection system consists of five attitude measurement units fixed on the human legs and waist.
A Curvature-Compensated, High Power Supply Rejection CMOS Bandgap Reference for MEMS Micro-Accelerometer
Authors: Liu Xiao Wei , Lv Bing Jun , Wang Peng Fei , Yin Liang , Xu Na
Published: July 2011

The reference is an important part in the accelerometer system. With the development of science and technology, the request of the performance of accelerometers is increasingly higher and the precision of reference directly affects the performance of accelerometers. Therefore, a reference voltage applicable to accelerometers is presented based on the analysis of basic principles of conventional bandgap reference (BGR) in this paper. A high-order curvature compensation technique, which uses a temperature dependent resistor ratio generated by a high poly resistor and a nwell resistor, effectively serves to reduce temperature coefficient of proposed reference voltage circuit and to a large extent improve its performance. To achieve a high power supply rejection ratio (PSRR) over a broad frequency range, a pre-regulator is introduced to remain the supply voltage of the core circuit of BGR relatively independent of the global supply voltage. The proposed circuitry is designed in standard 2.0μm CMOS process. The simulated result shows that the average temperature coefficient is less than 2ppm/°C in the temperature range from -40 to 120°C. The improvement on temperature coefficient (TC) is about 10 times reduction compared to the conventional approach. And the PSR at DC frequency and 1kHz achieves -107 and -71dB respectively at 9.0V supply voltage.
Design of MMFCS for MAV Based on MEMS Sensor
Authors: Xiong Wei , Zhou Zhao Ying , Liu Xiao Yan
Published: July 2011

Micro Measurement and Flight Control System (MMFCS) is important for an autonomous Micro Aerial Vehicle (MAV) to accomplish a flight task. Being in small size, low speed and limited payload capacity, most conventional measurement and control system is no longer practical in Micro Aerial Vehicle (MAV). In this paper presents a study on micro-MMFCS system based on criteria of minimum size and low computational complexity to complete the autonomous fly. Via using MEMS sensors, the developed micro MMFCS is with a size of 65×40×12mm3 and a weight of 22g. A novel linear fusion algorithm with a linear (and simple) Kalman model is presented to get the roll and pitch angle, then, the controller is designed in the lateral and longitudinal control loop for the trajectory tracking. Examples of waypoint-based autonomous fly mission, using the micro-MMFCS system of a MAV with a wingspan of 380 mm, is presented, with the results demonstrate the effectiveness of the proposed system.
Fabrication of Silicon Nano-wire by Oxidation
Authors: Wang Xiao Fei , Zhang Yu Fei , Yu Kan , Yu Xiao Mei
Published: July 2011

In this paper, we report a method of fabricating silicon nano-wire based on thermal oxidation technique. In this method, we first fabricate a wider structure with traditional lithography, and then use a layer of silicon nitride as mask to oxidize silicon. At the same time, due to the lateral diffusion and oxidation of oxidant, silicon is consumed by oxidant and the width of the silicon structure will be reduced to nano range when we remove the silicon dioxide. The factors affecting the ratio of vertical and lateral oxidation, for example, the gentle slope caused by isotropic oxidation and the inhomogeneity of the sidewall of silicon nano-wire, are discussed at last. Our results should be useful in generating silicon–based nanospintronics devices with careful selection of the oxide parameters.
Fabrication and Testing of SOG Structure Flat Heat Pipes with Triangle Grooves
Authors: Liu Xiao Wei , Wang Chao , Han Tian , Dong Tian
Published: July 2011

A new kind of charging and sealing method for SOG (silicon on glass) structure micro heat pipe with triangular grooves is investigated. MHP (micro heat pipe) is fully charged in a vacuum atmosphere which is useful for preventing air intermingle. Experimental results shows that when the fill ration of working fluid is about 35%, thermal conductivity of MHP with ethanol as its working fluid has an improvement of 19% compared to empty MHP.
Electrodeposition of Copper Nano-Clusters at a Platinum Microelectrode for Nitrate Determination
Authors: Li Yang , Sun Ji Zhou , Bian Chao , Tong Jian Hua , Xia Shan Hong
Published: July 2011

Copper nano-clusters were electrodeposited onto the platinum microelectrode by cyclic voltammetry method to fabricate an electrochemical sensor for nitrate determination. The material properties and morphologies of freshly deposited copper layer were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Compared with the microelectrode surface modified by fixed potential deposition method, the surface modified by cyclic voltammetry electrodeposition is porous and has a larger effective surface area. The reduction of nitrate under acidic conditions (pH=2) was characterized by linear sweep voltammetry. The preliminary experimental results reveal that the microelectrode modified by cyclic voltammetry electrodeposition had higher sensitivity of 22.56 uA/mmol for nitrate detection within the concentration range from 0.1mmolL−1to 4mmolL−1.
Fabrication and Performance of Piezoelectric MEMS Generators Using Bulk PZT Films
Authors: Tang Gang , Liu Jing Quan , Liu He Sheng , Li Yi Gui , Yang Chun Sheng , He Dan Nong
Published: July 2011

In this paper, a MEMS-based piezoelectric energy harvester is studied and the whole fabrication process is discussed. The generator structure of composite cantilever with nickel metal mass is devised. MEMS related techniques such as UV-LIGA, ion etching, XeF2 dry etching, wet chemical etching are developed to fabricate the device. This key process includes the bonding a bulk PZT to a Si wafer, and thinning the PZT down to about 15µm in thickness after bonding by mechanical lapping and polishing method. Epoxy resin with a thickness of about 4µm is used as the intermediate adhesive layer. The formed generator is measured on vibration testing setup. The energy under the first resonant mode can be harvested, corresponding to the resonant frequency of 810 Hz . The maximum output voltage under the resonant operation is about 1.23Vp-p.
Study on the Performance of Gas Journal Bearings for Power MEMS
Authors: Zhang Hai Jun , Yang Qin
Published: July 2011

Gas journal bearings, which are used to support radial loads in a rotating machine, have somewhat unusual requirements in Power MEMS deriving from the extremely shallow structures. With the reference Knudsen number being included, the modified Reynolds equation for gas journal bearings based on Burgdorfer’s first order slip boundary condition is put forward. The boundary condition for modified Reynolds equation is given. The numerical method is employed to solve the modified Reynolds equation to obtain the pressure profiles, load capacities and attitude angles of gas journal bearings for Power MEMS under different reference Knudsen numbers and eccentricity ratios. Numerical analysis shows that the pressure profiles and non-dimensional load capacities decrease obviously with the reference Knudsen number increasing, and the attitude angle changes conversely. Moreover, when the eccentricity ratio is smaller, the effect of gas rarefaction on the attitude angle is less.
Analysis and Research of Piezoelectric Dynamic Weighing Sensor
Authors: Zhao Li Bo , Liang Jian Qiang , Zhao Yu Long , Wang Jian Zhu , Chen Wei , Li Yong , Jiang Zhuang De
Published: July 2011

The Kistler company has invented piezoelectric dynamic weighing sensors which are applied to determine dynamically axle load, speed and gross weight of the vehicle based on piezoelectric effect of quartz crystal. They mainly consist of load-carrying beams and sensitive elements. Focusing on the control of preload in design and fabrication, finite element method (FEM) is applied with ANSYS software to optimize structural sizes. The influence curve of the structural dimensions of load-carrying beam on the preload is analyzed. With the piezoelectric coupling analysis function, the preload influence on the sensor sensitivity is researched. FEM simulation results show that the critical dimensions of load-carrying beam as well as the deformation and wall thickness of cavity have significant impact on the preload. Further studies show that the sensor has the highest sensitivity with the reasonable deformation and wall thickness of the cavity. In this paper, a sensor with range of 150 kN has the highest sensitivity at the wall thickness of 2 mm and the deformation of 0.14 mm.
A Monolithic MEMS Accelerometer Process
Authors: Li Xiao Gang , Mei Yong , Huang Wen Gang , Zhang Zheng Yuan , Li Jian Gen , Feng Zhi Cheng
Published: July 2011

A monolithic MEMS accelerometer process was established. This process successfully combines our standard BiCMOS technology and MEMS surface micromachining technique. The acceleration sensing element is a kind of comb-finger structure which is built by polysilicon surface micromachining technique. The polysilicon structure is designed to form two capacitors for acceleration sensing. The external acceleration will cause the value of two capacitors to vary in different direction. That means one reduces if the other increases. It was integrated with the signal conditioning circuit. In a single die, the active devices including vertical NPN, lateral PNP, PMOS and passive devices such as capacitors, resistors were fabricated which was followed by the steps to form the acceleration sensing structure. The experiment indicates that the fabricated circuit has the function of sensing capacitive variation and with a scale factor of 100mV/g.
Performance Analysis of a Novel MEMS Terminational Latch Mechanism
Authors: Lv Yong Jia , Lou Wen Zhong , Liu Chuan Qin , Zhang Long Fei
Published: July 2011

A novel latch mechanism of centrifugal system in the MEMS fuze S&A mechanism was mechanically analyzed by FEA. By the analysis, the equation of resistance was determined, the same as the equation about the angular velocity of centrifugal system and the reliability of the slider inserting, which were validated by FEA. Setting different parameters in the analysis and comparing the speed curves of sliders inserting into the latches, one method was determined to reduce the vibrating of speed curve. According to the characteristic of MEMS fabrication technology and design requirement for latch mechanism, one of higher reliability and smaller amplitude oscillation of speed curve was selected to simulate when it was imposed by reverse force.
Experimental Research on Lift up and Drag Reduction Effect of Streamwise Travelling Wave Wall
Authors: Tang Fei , Yan Zi Lin , Wang Xiao Hao
Published: July 2011

Travelling wave wall used for Micro Air Vehicle flow control is studied to find out its drag reduction effect. Aerodynamic characteristics of the airfoil with and without a streamwise travelling wave on its surface are calculated. The interrelationship is also analyzed among lift, drag and ratio of motion phase speed to the external flow velocity. The flexible airfoil that can generate streamwise travelling waves is realized via electromagnetic coil actuation. Thirty-six coils are placed streamwisely under heat shrink film and magnets producing magnetic field are placed under coils. Every single coil is controlled by current to move vertically in harmonic motion with 30 degrees phase difference between adjacent ones. So heat shrink film is actuated, and streamwise travelling wave is generated. Meanwhile, a prototype is designed and tested in wind tunnel. The experimental aerodynamic data proves that streamwise traveling wave airfoil can increase lift and reduce air drag.
TCR of the Ni-Cr Thin Film Resistors Used in Piezoresistive Pressure Sensor
Authors: Xiao Li , Du Li Dong , Zhao Zhan , Fang Zhen , Xu Jing
Published: July 2011

In this paper, temperature characteristic of Ni-Cr thin film resistors is studied which have a low temperature drifting coefficient and used in a kind of metal piezoresistive pressure sensors based on MEMS technology. Normally, Ni-Cr alloys have a small temperature coefficient of resistance (TCR) compared with some other metal materials. But it depends on the composition of Ni and Cr in the alloy and on the annealing process under different temperature. Through the research of the effect of the composition of the alloy and annealing cycles, it is found that 50:50wt% Ni-Cr thin film has negative TCR and 80:20wt% NiCr thin film has positive TCR. Both of them have a small TCR and can improve the precision of piezoresistive pressure sensor.
Failure Mechanisms and Lifetime Simulation Method for Nano Scale CMOS Device
Authors: Cheng Ying , Kang Rui , Zhang Gan Ghua
Published: July 2011

In nano scale, the degradation failure mechanism for CMOS device such as hot-carrier injection, breakdown of thin oxides, electro-migration and NBTI (Negative Bias Temperature Instability) induced damage become a major reliability concern. Physics-of-Failure method is used in lifetime prediction of nano scale CMOS, which integrates loading condition, package, geometry and material with time-to-failure. Common lifetime models for these mechanisms are described and a method to estimate lifetime of nano-scale CMOS device, with simulation based on Physics-of-Failure. Through Failure Mode, Mechanism and Effect Analysis, failure mechanism and lifetime models are clarified and selected, as well as structure, material, processing parameters and environment conditions. Stress analysis, which includes electrical stress by EDA and thermal analysis by FEA (Finite Element Analysis) are carried out to acquire parameters in lifetime model. Damage accumulation algorism and competing theory are utilized to predict lifetime of the device. This method will help CMOS device design engineers better understand the failure mechanisms in nano-scale and take design-for-reliability measures.
Thermal Transport through Solid-Solid Interface with an Interlayer
Authors: Liu Ya Dong , Bi Ke Dong , Chen Yun Fei , Chen Min Hua
Published: July 2011

Nonequilibrium molecular dynamics (NEMD) approach is developed to investigate the thermal transport across a solid-solid interface between two different materials with an interlayer around it. The effects of system size and the interlayer material’s properties on the interface thermal resistance are considered in our model. The NEMD simulations show that the addition of an interlayer between two highly dissimilar lattices depresses the interface thermal resistance effectively. Meanwhile, the effective thermal conductivity along the direction of heat flux is enhanced with the increasing system temperature. Moreover, the interface thermal resistance after including an interlayer does not depend strongly on the simulation system size.
Dielectric Constant Measurement of Liquids Using Nanosecond-Pulsed Signals
Authors: Sun Wei Qiang , Yang Yong , Xu Sheng Yong
Published: July 2011

In this paper, we report a novel method to measure the dielectric constant of various liquids of limited amount. The liquid under test is sealed in a coaxial-like test device. The dielectric constant is determined by comparing the delay of a nanosecond-pulsed signal traveling through the test device with that traveling through a reference coaxial cable. The results show that the maximum error of this kind of measurement is within 15-30%, which is good enough for a semi-quantitative estimation of the dielectric constant of an unknown liquid, especially when the amount of the liquid is not enough for investigation with other existing approaches.
The Study of Humidity Effect on Self-Heated Surface Micromachined Polysilicon Resistor
Authors: Ma Hong Yu , Zhang Wei Dong , Ding En Jie
Published: July 2011

Polysilicon is a very attractive material in microelectronics for thermal sensors. In this paper, the effect of humidity on thermal resistance of surface micromachined polysilicon is invested. It is found that the thermal conductivity variation of air due to humidity changes the suspended polysilicon resistor evidently. This property could be used as the working principle of relative humidity sensor.
Piezoresistive Sensitivity and Al Ohmic Contact of Highly Doped Polycrystalline Silicon Nano Thin Films
Authors: Shi Chang Zhi , Liu Xiao Wei , Wu Xuan , Zheng Hai Tao
Published: July 2011

The piezoresistive and ohmic contact properties of polycrystalline silicon nano thin films were investigated in this paper. The polycrystalline silicon films with different thicknesses and doping concentrations were deposited by LPCVD and doped with boron highly, and then the cantilever beam samples were fabricated by photolithography and wet etching. By measuring the gauge factor and specific contact resistivity, the specific contact resistivity of Al contacts can reach 2.4×10-3Ω·cm2 after the alloying at 450 °C for 20 min; the enhanced piezoresistive effect of highly doped polycrystalline silicon nano thin films was discovered. The conclusions indicated that the enhanced piezoresistive sensitivity of PNTFs is due to the modification of depletion region barrier by ultra high doping and film thickness thinning and the enhancement of tunneling piezoresistive effect. The distinct piezoresistive phenomenon of PNTFs could be utilized for the development and fabrication of miniature piezoresistive sensors.
Design and Empirical Study for Coner Compensation in 25% Wt TMAH Etching on (100) Silicon Wafers
Authors: Niu Zheng Yi , Wu Xue Zhong , Dong Pei Tao , Xiao Ding Bang , Hou Zhan Qiang , Chen Zhi Hua , Zhang Xu
Published: July 2011

Anisotropic wet etching is a key processing step for the fabrication of microstructures. In general, convex corner structures and non {111} crystal planes will be undercut during wet anisotropic etching. This characteristic of Si is an obstacle to the fabrication of structures in various applications. Among a number of silicon etchants, TMAH is becoming popular for low toxicity and CMOS compatibility. In this paper, a new design of compensation structure has been proposed to solve the undercutting problem with 25%wt TMAH solution. The new compensation structure is made up by squares which are connected to the convex corner. An empirical expression between the parameters of the new compensation structure and etching depth is derived. The changes of the compensation structure in different etching process are shown by photographs. Experimental results prove the high accuracy of this method. Compared to two widely used compensation structures, the new structure is more space efficient.
Environmental Barrier Coatings for Silicon Nitride
Authors: Chen Hong Fei , Klemm Hagen
Published: July 2011

Ytterbium silicate layers were deposited on Si3N4 ceramics as environmental barrier coatings (EBCs) by a dip coating-sintering method. Coated samples were tested in an atmosphere simulating the practical conditions of a gas turbine to investigate water vapor corrosion and recession mechanisms of ytterbium silicate coatings. Prior and after tests, phase compositions and morphologies of the coatings varied as the consequence of the formation of silica at the coating/substrate interface. Due to the evaporation and diffusion of silica into the upper layer, a porous interface was finally found, which led to the spallation of coating.
Optical and Tribological Properties of Silicon Carbide Thin Films Grown by Reactive DC Magnetron Sputtering
Authors: Tavşanoğlu Tolga , Baskurt Erdem , Onüralp Yücel
Published: July 2011

In this study, SiC films were deposited by reactive DC magnetron sputtering of high purity (99.999%) Si target in Ar/CH4 gas mixture. Three types of substrates, AISI M2 grade high speed steel, glass, and Si (100) were used in each deposition. Films were grown with different compositions at 50 oC and 250 oC by varying (0–50 %) CH4/Ar processing gas ratios. Microstructural properties of SiC films were characterized by cross-sectional FE–SEM (Field–Emission Scanning Electron Microscope) observations. XRD (X–Ray Diffractometer) results indicated that films were amorphous. Friction coefficients as low as 0.1 were obtained from SiC coatings against Al2O3 balls, according to the tribological tests. Optical investigations showed that the transparency and opacity of SiC films could easily be tailored by modifying Si and C concentrations in the coatings.
Characterization of Thermal Properties of Micro-Sized Ceramic Powders for APS Deposition of Ceramic Layers
Authors: Moskal Grzegorz , Iwaniak Aleksander , Rozmysłowska-Grund Aleksandra
Published: July 2011

The paper presents test results concerning characteristics of the selected thermal properties of ceramic powders based on rare earth zirconates with a pyrochlore structure of RE2Zr2O7 type, intended for thermal spraying of TBCs. Gadolinium, lanthanum, samarium and neodymium based powders were tested. The scope of the tests encompassed thermal diffusivity analysis of the powders in a compressed pellets form within temperature range 25-1500°C, and also tests of specific heat and thermal expansion coefficient within similar temperature range. Standard powder of 8YSZ type on the basis of zirconium oxide modified with yttrium oxide was used as a reference material. Specific heat measurements of the powders showed that the highest values within the entire test temperature range were obtained for the standard YSZ type powder. In the case of new type of powders, the results obtained are very similar and only slightly lower in comparison with YSZ powder. The lowest values were obtained for the samarium based powder (temperature range corresponding to operating temperature). Character of the curves obtained do not show course of strong reactions connected with phase changes. Dilatometric tests of materials made it possible to determine thermal expansion coefficient. Mean coefficient values are included within the range from 5.5 x 106mm/°C to 10.0 x 106mm/°C. The highest mean value of thermal expansion coefficient was obtained for Nd2Zr2O7 powder and the lowest one for La2Zr2O7 powder. The lowest thermal diffusivity value at room temperature was shown by Nd2Zr2O7 powder, and the highest one by 8YSZ powder (0.215 mm2/s).
Fabrication of AlN/Al2O3 Coatings via Atmospheric Reactive Plasma Nitriding of Al2O3 Powders
Authors: Shahien Mohammed , Yamada Motohiro , Yasui Toshiaki , Fukumoto Masahiro
Published: July 2011

Plasma sprayed alumina (Al2O3) coatings has showed a great effect in service the life of engineering tools, while its low thermal conductivity limits its application in heat exchange applications. Aluminum nitride (AlN) is a promising material to improve the thermal conductivity of Al2O3 coatings. This paper proposed a new way to fabricate AlN/Al2O3 coatings through reactive plasma nitriding of Al2O3 powders. It was possible to fabricate cubic-AlN/Al2O3 coatings by spraying Al2O3 powders in atmospheric plasma spray process (APS). During plasma Al2O3 powder reacted in high temperature N2/H2 plasma to form aluminum oxynitride and it easily nitride to produce the cubic AlN phase. Thus, both of Al5O6N and c-AlN phrases have the same cubic symmetry (cubic and closely packed crystal structure). Then, the particles collide, flatten, and rapidly　solidified on substrate surface. The high quenching rate of the plasma flame prevents the crystal growth and formation of hexagonal AlN phase. The fabricated coatings consist of c-AlN, α-Al2O3, Al5O6N and γ-Al2O3. The AlN content was improved with increasing the flight time (spray distance) due to increasing the reaction time between Al2O3 particles and the surrounding N2 plasma. It was possible to fabricate AlN/Al2O3 coating consist of 97 wt. % of AlN phase at the spray distance of 300 mm.
Fabrication and Evaluation of Arrayed Needle-Like TiO2 Particle – Transparent Resin Composite Films
Authors: Kikitsu Shin Ichi , Otsuka Takaaki , Miyazaki Hidetoshi , Suzuki Hisao , Ota Toshitaka
Published: July 2011

Needle-like TiO2-resin composite films were fabricated using needle-like TiO2 particle filler and urethane matrix. The needle-like TiO2 particles in the composite film were arrayed completely under the fabrication condition of applying AC bias of 10 volt with 0.1 Hz for 4 hr, and the transmittance of the resulting composite film showed angularly dependence. The needle-like TiO2 particles in the composite were oriented quickly by a larger applying bias. Furthermore, increase of the mixing ratio of TiO2 particles in the composite film caused increasing an angularly dependence of the transmittance of the composites.
Ternary Phase Relation on Preparation of YBa2Cu3O7-δ Films by Laser CVD
Authors: Zhao Pei , Ito Akihiko , Tu Rong , Goto Takashi
Published: July 2011

c-axis-oriented YBa2Cu3O7- films were prepared by laser chemical vapor deposition (laser CVD) using Y(DPM)3, Ba(DPM)2/Ba(TMOD)2 and Cu(DPM)2 as precursors with enhancement by a continuous wave Nd:YAG laser. YBa2Cu3O7- film almost in a single phase and that with different second phases of BaCuO2, CuBaO2, BaY2O4, CuYO2, Y2O3 and CuO were obtained by varying evaporation temperature of precursors. Ternary phase diagram as a function of evaporation amount of three precursors were obtained. The deposition rate of the c-axis-oriented YBCO film was 60 µmh-1, about 60–600 times higher than those of conventional CVD.
Hydroxyapatite Nano-Barium-Strontium-Titaniumoxide Composites
Authors: Demirkol N. , Kayali Eyup Sabri , Yetmez Mehmet , Oktar F.N. , Agathopoulos Simeon
Published: July 2011

The aim of this study is to produce and to investigate the mechanical and microstructural properties of composite materials made of hydroxyapatite, obtained from natural bovine bone and nano barium strontium titanium oxide (5 and 10 wt%). Compositions were mechanical alloyed and compacted to pellets. The samples were subjected to sintering at different temperatures between 1000oC and 1300oC. Compression strength, Vickers microhardness as well as density were measured. SEM and X-ray diffraction studies were also conducted. With increasing sintering temperature, microhardness, compression strength and density of composites increased. With increasing addition of nano barium strontium titanium oxide (BST) to bovine hydroxyapatite (BHA), microhardness values of composites decreased at all sintering temperatures, but compression strength and density values of composites showed different tendency. Compression strengths of BHA-composites at low sintering temperatures were nearly the same, but their compression strengths at high sintering temperatures decreased with increasing nano BST addition. The best mechanical properties were obtained at 1300°C sintering temperature with BHA-5wt% nano BST. Microhardness and compression strengths values of these nano–oxide composites are generally higher than that BHA-composites produced by traditional methods. Adding of nano-oxides to BHA could be a valuable method to produce rigid and high load carrying ability when compared with BHA-composites produced by conventional methods. Nano-HA and nano-oxides composites could be even better. Those nano-nano studies are still in progress.
Oxidation Behavior of ZrB2-15vol.%SiC at an Oxygen Partial Pressure of 57 Pa
Authors: Momozawa Ai , Kubota Yuuki , Tu Rong , Goto Takashi , Takagi Ken-Ichi , Komurasaki Kimiya , Hatta Hiroshi
Published: July 2011

The oxidation tests of the ZrB2-15vol.%SiC composite were carried out at 1673-1923 K under a low partial pressure of oxygen. Cross sections of the oxidized samples were studied using WDS. The reaction layer consists of ZrO2 and SiO2 at 1673 K. The SiO2 protective layer is formed on the surface. No apparent SiC depleted layer is observed. SiC depletion seems to occur at 1923 K and only the ZrO2 phase exists at the reaction layer. The passive oxidation occurs at 1673 K, whereas the active oxidation at 1923 K. The mass changes are quantitatively discussed by introducing a new emprical equation. The ZrB2-30 vol.%SiC composite is also discussed briefly.
Joining of SiC by Tape-Cast SiC-Al2O3-Y2O3 Interlayer
Authors: Tian Wu Bian , Kita Hideki , Hyuga Hideki , Kondo Naoki
Published: July 2011

SiC substrates were successfully bonded by tape-cast SiC-Al2O3-Y2O3 interlayers in the temperature range of 1800-1900 °C for 60 min at 15 MPa pressure in flowing Ar. Based on microstructure observations, we find that the α-SiC interlayers result in equiaxed microstructure at all joining temperatures while the tape-cast β-SiC leads to a microstructure varying from a mixed characteristic to an elongated one with joining temperature. The detailed image analysis suggests the close interlayer thickness, the quicker grain growth rate of β-SiC relative to α-SiC one and the good agreement between aspect ratio and morphology in all joints. Moreover, the SiC grains of interlayer near to interface develop preferentially from the external SiC grains of substrate, which is possibly related to the morphology difference between substrate and interlayer and the grain growth behaviors. Finally, the SiC joined with tapes exhibits an average bending strength over 359 MPa and usually fracture within SiC bases.
Friction Surface Damage of Carbon-Fibre Reinforced Carbon-Silicon Carbide Composites (Cf/C-SiC)
Authors: Wu Hou Zheng , Wang Yuan
Published: July 2011

Carbon-fibre reinforced carbon-silicon carbide composites (Cf/C-SiC) has increasingly drawn the attention of designers and engineers of transport vehicles and friction components due to the outstanding combination of low density and high tolerance to mechanical/thermal damage across a wide range of temperatures. However, the lack of enough understanding of tribology and hands-on experience in application could create pitfalls for composites design, and be disappointed in engineering application. Through the study of the friction surface using post-mortem microstructural analysis, we have demonstrated that the friction surface development varies largely from one constituent to another. Friction debris could form a strong bond on the surface of silicon, but unlikely on that of carbon fibre and silicon carbide. Silicon carbide regions could undergo an excessive ductile deformation that led to the development of kinks or microcracks on the friction surface.
Silicon Nitride Grain Boundary Glasses: Chemistry, Structure and Properties
Authors: Hampshire Stuart , Pomeroy Michael J.
Published: July 2011

Silicon nitride is recognised as a high performance material for both wear resistant and high temperature structural applications. Oxide sintering additives such as yttrium oxide and alumina are used to provide conditions for liquid phase sintering, during which the additives react with surface silica present on the Si3N4 particles and some of the nitride to form an oxynitride liquid which allows densification and transformation of - to -Si3N4 and on cooling remains as an intergranular oxynitride glass. This paper provides an overview of liquid phase sintering of silicon nitride ceramics, grain boundary oxynitride glasses and the effects of chemistry and structure on properties. As nitrogen substitutes for oxygen in oxynitride glasses, increases are observed in glass transition and softening temperatures, viscosities, elastic moduli and microhardness. These property changes are compared with known effects of grain boundary glass chemistry in silicon nitride ceramics.
The Effect of Heat-Treatment on Thermal Conductivity of Silicon Nitride Ceramics
Authors: Yoshida Katsumi , Sekimoto Yuki , Katayama Keiichi , Wasanapiarnpong Thanakorn , Imai Masamitsu , Yano Toyohiko
Published: July 2011

Alpha- or beta-Si3N4 powder with larger grain size was uses as starting material, and the effect of heat-treatment on thermal conductivity of Si3N4 ceramics using MgO, Y2O3 and SiO2 as sintering additives was investigated in terms of their microstructure and the amount of grain boundary phase. Most of the components derived from sintering additives existed as glassy phase in sintered Si3N4. After heat-treatment at 1950oC for 8 h, the amount of glassy phase significantly decreased, and then small amount of glassy phase existed in Si3N4 ceramics was crystallized as Y2O3 and Y2Si3N4O3. In the case of Si3N4 ceramics using SN-7 powder, thermal conductivity of heat-treated Si3N4 was around twice of the value of sintered Si3N4, and the thermal conductivity was increased from 41.4 to 87.2 W/m•K due to not only the reduction of grain boundary phase but also the grain growth. In the case of Si3N4 using SN-F1 powder, thermal conductivity of Si3N4 ceramics was also significantly increased from 36.0 to 73.2 W/m•K after heat-treatment. In this case, the reduction of grain boundary phase mainly affected the thermal conductivity of Si3N4 ceramics because the grain size of heat-treated Si3N4 was nearly the same as that of sintered Si3N4. The reduction of grain boundary phase from Si3N4 was effective for the improvement of their thermal conductivity in addition to grain growth of Si3N4.