应用于体声波谐振器的ZnO薄膜结构和电学特性

采用直流磁控溅射的方法制备了ZnO压电薄膜,并在双面抛光的熔融石英基片上制备了高次谐波体声波谐振器.x射线衍射结果显示ZnO压电薄膜C轴择优取向明显,衍射峰半高宽为0.1624°,显示出较好的结晶质量;扫描电镜分析观察到ZnO垂直于基片表面的柱形晶粒结构和较平滑的薄膜表面.体声波器件的电学测试结果显示器件具有很好的多模谐振特性,说明ZnO压电薄膜很好地激发出了厚度方向的纵声波,可应用于体声波器件和声表面波器件中.另外采用间接的方法得到ZnO压电薄膜在870MHz时的介电常数约为5.24,介电损耗因子为1.07,进一步减小介电损耗因子,可以提高器件的Q值.     

2.4GHz射频薄膜体声波谐振器的研制

提出了基于ZnO压电薄膜多层结构的2.4GHz射频薄膜体声波谐振器,并进行了研究.采用修正后的Mason等效电路模型对器件的谐振特性进行了分析和模拟.给出了采用MEMS工艺制备器件的工艺流程,并利用射频网络分析仪对实验器件进行了测试.利用多点数值拟合的方法消除射频测试中引入的寄生分布参数,提取出器件的实际参数:器件的串联谐振频率fs和并联谐振频率fp分别为2.3714GHz和2.3772GHz,相应的有效机电耦合系数为0.598%;串联谐振频率处和并联谐振频率处的Q值分别为500.3和425.5,f·Q值乘积达到1.2×1012.该谐振器器件的有效直径为200μm,样品实际尺寸为1.2mm×1.2mm×0.3mm,可用来制备体积小、高性能和低相噪的射频振荡器.     

固贴式薄膜体声波谐振器性能受压电材料的影响分析

利用Math CAD软件对固贴式薄膜体声波谐振器(SMR-FBAR)器件建立数学模型进行仿真,分析了不同压电薄膜材料和厚度,不同电极材料和厚度对FBAR器件谐振特性的影响。采用射频磁控溅射方法制备氮化铝(AlN)薄膜,利用扫描探针显微镜中的压电力显微镜(PFM)模块对AlN薄膜的压电性能进行了测试。得到主要结论为:复合FBAR的谐振频率因为增加了电极厚度因素相比理想FBAR的谐振频率偏低;压电材料的机电耦合系数对器件带宽起决定性作用,器件的机电耦合系数正比于材料的机电耦合系数;AlN具有较高的压电系数,可以有效提升器件性能,增大带宽,适合作为压电薄膜材料;采用小尺寸压电薄膜和电极厚度有益于提高器件的频率。     

AlN薄膜腔声谐振器的制备及性能研究

采用体硅微细加工工艺制备了基于AlN压电材料的薄膜腔声谐振器，研究了器件结构中谐振区形状和面积对谐振器性能的影响。以X射线衍射仪、扫描电镜表征了AlN压电薄膜的结构及形貌，高频网络分析仪表征谐振器频率特性。测试结果表明，谐振器所用AlN压电薄膜具有C轴择优取向及良好的柱状晶结构；器件频率特性良好，谐振频率达1．759GHz，机电耦合系数3．75％，品质因数79．5。通过研究不同谐振区形状、面积谐振器的性能，明确了结构因素对器件频率特性的影响，分析了其中的机制。     

流式细胞仪中压电扫描振镜的设计

针对流式细胞成像的应用需求,设计了一维压电扫描振镜并进行了性能测试.该振镜利用微铰链梁将压电片的伸缩振动转化为反射面的旋转振动.首先,通过有限元仿真对压电振镜进行结构建模和性能分析,得到了振镜的工作模态以及扫描频率和最大扫描角度随结构尺寸的变化关系.接着,制备了由压电片和硅片基底组成的振镜样机.最后,利用角度测量系统对振镜的扫描特性和频响特性进行了测试.实验结果表明:2 mm×2 mm的反射面在12Vpp的电压驱动下可在谐振频率10.034 k Hz处产生14°的扫描角度,在5.2Vpp的电压驱动21.26 k Hz的高频谐振下,仍可以产生3.35°的扫描角度.振镜样机Q值达865,扫描角度与驱动电压幅值呈线性关系.该振镜具有较大的镜面尺寸和较高的扫描频率,可满足流式细胞扫描成像快速和高分辨率的应用需求.     

AlN薄膜体声波谐振器研究

采用一维Mason模型,研究了体声波谐振器的频率特性,探讨了压电薄膜AlN和上电极膜厚对谐振频率的影响,压电参数d33及压电薄膜与电极的厚度比率对机电耦合系数的影响,同时研究了谐振区域的面积和声能在衬底中的损耗对品质因数的影响.测量的体声波谐振器频率特性曲线与模拟结果吻合的较好.     

基于压电效应的声能量收集

对圆盘式压电能量收集器在声场作用下的电能输出效果进行了研究。将处于夹持状态的压电陶瓷片,放置在单频稳态的正弦波形声场中,由于激振作用,压电陶瓷片会产生形变。实验结果表明,在器件处于谐振状态时输出电压和功率会达到最大值。在正弦声场中,当声波频率达到907 Hz的谐振频率时压电陶瓷片的开路输出电压可以达到4.6 V;在110 dB的声场中,当负载电阻达到11.2 kΩ时,输出功率最大可达60.4μW。     

以四面体非晶碳为布拉格反射栅高声阻抗材料的固贴式薄膜体声波谐振器性能仿真分析

为了提高固贴式薄膜体声波谐振器(SMR)的电学和声学品质,实现四面体非晶碳(ta-C)在体声波器件领域的新应用,建立了以ta-C为布拉格反射栅高声阻抗材料的SMR模型,利用MathCAD仿真研究布拉格反射栅层数对该SMR的谐振特性的影响以及ta-C中sp3杂化含量和高/低声阻抗层厚度偏差对SMR的品质因子(Q值)的影响。结果表明层数的增加提高了SMR的品质;ta-C薄膜sp3杂化含量越高,达到饱和Q值所需层数越少,当含量为80%时,至少需要6层(3对)布拉格反射层使SMR达到优异Q值;距离压电堆越近的高/低声阻抗层,其厚度偏差对Q值的影响越大,从而实现了高频率(8GHz)低损耗的SMR的设计。     

固贴式薄膜体声波谐振器用材料体系研究进展

固贴式薄膜体声波谐振器(SMR-FBAR)技术是近年来电子工业领域里的突破性技术,具有2GHz以上的工作频率、极高的的品质因子及良好的机械稳定性等众多的优异特性.基于其独特的优越性,固贴式薄膜体声波谐振器成为了科研工作者们关心的热点,并在第三代无线通信系统中已得到广泛应用,例如作为基本单元用来制作滤波器、双工器和振荡器等第三代无线通信系统中的频率选择器件.器件选用的材料体系是决定器件性能的关键因素.本文以器件结构为线索,综述了固贴式薄膜体声波谐振器用材料体系的研究进展,包括压电薄膜(氮化铝、氧化锌等)、高/低声阻抗材料以及电极薄膜,讨论了材料性能和器件性能的关系,并对材料体系下一步的研究方向进行了展望。     

基于COMSOL的声表面波器件仿真

声表面波器件在通信、传感、射频识别等领域有着广泛的应用.以有限元方法为基础,利用有限元软件COMSOL对声表面波器件进行了仿真.从器件的模型建立入手,按由浅入深的顺序对无电极压电基片、压电基片表面沉积叉指换能器、叉指换能器表面溅射薄膜、薄膜上负载液体的4种结构进行了仿真分析.仿真研究表明:叉指换能器的电极效应会产生正、反特征频率,并且两种频率都随着叉指电极的敷金比与高度增加而向低频偏移;薄膜厚度的增加同样会导致器件频率向低频变化;当器件负载液体用于液体密度检测时,可通过器件频率变化对液体密度的灵敏程度来对薄膜厚度进行优化.其研究结果可以为声表面波器件的设计制作提供依据.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.