基于MEMS技术的原子气室封装工艺

在基于MEMS技术原子气室的制备工艺中，难度较大的是碱金属的填充技术及阳极键合封装工艺，该工艺流程直接影响原子气室的质量。为进一步简化原子气室的制备工艺，设计了“双腔式”原子气室结构，采用先阳极键合，再化学反应的方法实现了原子气室批量化的封装。单个原子气室体积为6 mm×4 mm×2.5 mm,经氦气细检漏气率平均达到5×10^-8 Pa·m³·s^-1,通过搭建实验平台，测得了不同温度下的原子气室D1线吸收谱线图，实验结果表明原子气室封装成功。     

基于pH-ISFET片上系统的研究

采用标准CMOS工艺实现了基于pH-ISFET微传感器与读出电路的单芯片集成,该芯片包括差分结构ISFET/REFET传感器、金属准参比电极、恒流源和前级读出电路.芯片采用商用0.35μm,4-金属和2-多晶硅标准CMOS工艺流片,整个芯片面积2mm×2.5mm,工作电压3.3V.在标准CMOS工艺代工的基础上,设计并实现了合理的后续工艺流程.微传感系统获得53.65mV/pH的灵敏度和很好的线性度.由此说明,把ISFET微传感阵列与集成电路集成在单个芯片上构建智能型片上系统(SOC)是完全可能的,应用前景良好.     

吸收光谱型气体红外传感器的设计与实现

对一种吸收光谱型气体红外传感器的工作原理、设计原理和集成化设计进行了分析.其中气体浓度对光谱的吸收会影响光强的变化,所以将微型热释电红外敏感头、小型灯泡都集成在1个小型的气室中,气室中有2个通道,气体探测通道和参考通道.2个通道光强的强弱差就会体现出气体浓度的大小,这样就实现了测试气体浓度的功能.集成化采用MEMS工艺将红外双路敏感元件及滤光片制作成探测头,然后通过微封装和微小集成技术将探测头、红外光源、过滤网集成在气室内.     

毫米波有源相控阵射频前端集成制造技术

毫米波有源相控阵射频前端工艺集成度高,立体组装、先进封装材料、TR组件热路设计和芯片技术是实现有源相控阵射频前端集成制造的关键技术.综合国内外研究发展现状,系统封装、综合集成以及多功能芯片技术是有源相控阵射频前端集成制造技术的未来发展趋势.     

一种适用于MEMS陀螺仪的高性能电容读出电路

针对音叉式体硅MEMS陀螺仪传感器,提出了一种新颖的电容读出电路结构,该结构对共模电压漂移不敏感,能消除电容不匹配引入的误差.相关双采样(CDS)技术有效降低了电路的低频噪声和电压失调的影响.采用了一种简化的微陀螺传感器仿真模型,用于读出电路与微传感器的联合仿真.读出电路在0.35 μm 2P4M标准CMOS工艺下设计流片,芯片面积为2.5 mm×2.5 mm,5 V电源电压,电路工作在500 kHz的时钟频率下,实现了1.5 aF/Hz1/2的电容分辨率和大于100 dB的动态范围.     

基于STM32的微量硫化氢检测系统设计

硫化氢(H_2S)在经天然气脱硫过程后含量较低,需连续检测,目前国内对微量H_2S的检测研究设计较少。本文使用高灵敏度硫化氢传感器,采用STM32系列主控芯片,基于电化学原理,进行一种微量H_2S检测系统设计。以可编程的低噪声AD7794作数模转换,对电化学反应电流进行精准采集;设计过程中,对检测气室的温度、压力及流量采取在线监测以确保实验设计的标准环境,各项实验数据以Modbus协议与HMI触摸屏交互,该装置采用了自主研制的信号处理模块和供电模块,便于集成。测试结果表明:所设计的H_2S检测装置对含量10ppm的H_2S标准气体检测波动范围小于±0.1ppm,可满足二类天然气检测要求。     

新型运载火箭中电容式液位传感器接口专用集成电路

为了提高新型航天运载火箭中电容式液位传感器系统的电容检测性能,设计了一款适用于航天运载火箭中电容式液位传感器的接口专用集成电路(Application Specitic Integrated Circuit,ASIC)芯片。首先,完成了整体电路的系统级设计,实现了对电容式液位传感器输出电容的线性检测,将传感器输出电容量转化为与之呈线性关系的电压量输出。然后,对接口ASIC芯片的线性度、噪声特性和温度环境适应性进行了理论分析与研究。最后,采用0.5μm CMOS工艺完成接口ASIC的流片,并进行了芯片的性能测试。实际测试结果显示,芯片电容检测非线性为0.005%,输出噪声密度3.7aF/Hz~(1/2)(待测电容40pF),电容测量稳定性7.4×10-5 pF(参考电容40pF,待测电容40pF,1σ,1h),输出零位温度系数4.5μV/℃。测试结果证明,该接口ASIC的电容检测性能已经达到国外最高性能的电容式液位传感器液位测量芯片的水准,可以广泛应用到多种电容式检测传感器中。     

硅微振动陀螺仪设计与性能测试

介绍了基于DDSOG(Deep Dry Silicon On Glass)工艺自主研发的硅微振动陀螺仪的结构,封装,及信号与性能检测.利用结构解耦的方法和DDSOG工艺设计和制备了双质量线振动式陀螺结构.为了提高它的机械灵敏度、可靠性和长期稳定性,采取真空封装技术实现了器件级真空封装,并消除了轴向加速度等共模干扰的影响.陀螺电路采用自激闭环驱动、开环检测的方式,简化了电路.为了降低环境温度对陀螺零偏的影响,研究了既定范围内陀螺的输出特性,建立了陀螺输出与温度之间的关系模型,设计了温度补偿电路,降低了陀螺整表的功耗和体积.对采用上述技术的硅微陀螺仪进行了性能测试,测试结果表明,陀螺Q值＞100 000,量程为±500(°)/s,标度为21.453 mV·(°)-1s-1,非线性和对称性分别为36.905×10-6和184.125×10-6.常温下陀螺零偏稳定性为7.714 3(°)/h,带宽为100 Hz,整表体积为31mm×31mm×12mm,功耗为288 mW.该陀螺仪性能好、体积小、功耗低,在中等精度的惯性导航系统中有较好的应用前景.     

Bell-Bloom型SERF原子磁力仪综述

弱磁检测技术可应用于地球物理探测、医学、军事等诸多领域。随着弱磁检测技术的不断提升,磁力仪的发展十分迅猛。近些年,无自旋交换弛豫原子磁力仪超越了超导量子干涉磁力仪成为目前世界上最灵敏的磁强计。首先介绍了无自旋交换弛豫原子磁力仪超高灵敏度的根本原因-无自旋交换弛豫现象,以及Bell-Bloom型无自旋交换弛豫原子磁力仪机理;接着给出了国内外最常用的Bell-Bloom型无自旋交换弛豫原子磁力仪的装置结构,并对其各组成部分加以详细描述分析;根据原子磁力仪的不同工作模式,归纳出3种系统设计方案并对其优缺点和适用场合进行对比;最后,对其灵敏度、响应带宽和实用集成化三方面进行论述,指出Bell-Bloom型无自旋交换弛豫原子磁力仪具有广泛应用前景。     

应用于反射式编码器的光电集成芯片设计

为满足反射式光电编码器的应用需求，设计一款集成光电二极管阵列、跨阻放大器、全差分放大器以及偏置电路的光电芯片。首先，根据反射式编码器的成像原理设计光电二极管阵列。然后，设计可调增益跨阻放大器、全差分驱动放大器级联作为增量信号处理链路，降低读出信号的噪声同时提高带负载能力。接着，集成具有宽电源电压输入范围以及较好的电源纹波抑制能力的偏置电路。基于0.35μm光电CMOS工艺进行流片，通过搭建测试环境，光电集成芯片可以在3.5～6 V宽电源电压范围内正常工作，且在电机转速6 000 r/min内输出的增量信号正交性良好。角度测量结果表明，正反转情况下角度测量误差最大值分别为4.752″和5.04″。在5 V供电电压下电路的直流功耗为66.5 mW，整体芯片面积为5.91 mm×2.81 mm。能够满足光电芯片高度集成化、较好的信号正交性、宽电源电压输入范围、高电源纹波抑制能力等要求，适用于反射式光电编码器。     

Ferrule-top atomic force microscope

Ferrule-top cantilevers are a new generation of all-optical miniaturized devices for utilization in liquids, harsh environments, and small volumes [G. Gruca et al., Meas. Sci. Technol. 21, 094033 (2010)]. They are obtained by carving the end of a ferruled fiber in the form of a mechanical beam. Light coupled from the opposite side of the fiber allows detection of cantilever deflections. In this paper, we demonstrate that ferrule-top cantilevers can be used to develop ultra compact AFMs for contact mode imaging in air and in liquids with sensitivity comparable to that of commercial AFMs. The probes do not require any alignment procedure and are easy to handle, favoring applications also outside research laboratories.     

The influence of atomic vibrations on the imaging properties of atomic focusers

The resolving power of atomic focusers consisting of from one to several gold atoms in a column is examined through consideration of the optical transfer function of the system. It is found that resolutions better than 0.1 nm are possible for ten-atom focusers, but for greater numbers of atoms the effects of atomic vibrations degrade the resolving power. For accurate characterization of the transfer function it is necessary to take into account electrons which have transferred vibrational energy to the focuser.     

Recirculating atomic beam oven

We describe an atomic beam oven that reuses alkali metal in the unused portion of the beam. This is accomplished by condensing the desired vapor on a cooled jacket from which it may be drained back into the oven.     

Print your atomic force microscope

Progress in scanning probe microscopy profited from a flourishing multitude of new instrument designs, which lead to novel imaging modes and as a consequence to innovative microscopes. Often these designs were hampered by the restrictions, which conventional milling techniques impose. Modern rapid prototyping techniques, where layer by layer is added to the growing piece either by light driven polymerization or by three-dimensional printing techniques, overcome this constraint, allowing highly concave or even embedded and entangled structures. We have employed such a technique to manufacture an atomic force microscopy (AFM) head, and we compared its performance with a copy milled from aluminum. We tested both AFM heads for single molecule force spectroscopy applications and found little to no difference in the signal-to-noise ratio as well as in the thermal drift. The lower E modulus seems to be compensated by higher damping making this material well suited for low noise and low drift applications. Printing an AFM thus offers unparalleled freedom in the design and the rapid production of application-tailored custom instruments.     

A heated vapor cell unit for dichroic atomic vapor laser lock in atomic rubidium

The design and performance of a compact heated vapor cell unit for realizing a dichroic atomic vapor laser lock (DAVLL) for the D(2) transitions in atomic rubidium is described. A 5 cm long vapor cell is placed in a double-solenoid arrangement to produce the required magnetic field; the heat from the solenoid is used to increase the vapor pressure and correspondingly the DAVLL signal. We have characterized experimentally the dependence of important features of the DAVLL signal on magnetic field and cell temperature. For the weaker transitions both the amplitude and gradient of the signal are increased by an order of magnitude.     

Cross-talk correction in atomic force microscopy

Commercial atomic force microscopes usually use a position-sensitive photodiode to detect the motion of the cantilever via laser beam deflection. This readout technique makes it possible to measure bending and torsion of the cantilever separately. A slight angle between the orientation of the photodiode and the plane of the readout laser beam, however, causes false signals in both readout channels. This cross-talk may lead to misinterpretation of the acquired data. We demonstrate this fault with images recorded in contact mode on periodically poled ferroelectric crystals and present a simple electronic circuit to compensate for it. This circuit can correct for cross-talk with a bandwidth of approximately 1 MHz suppressing the the false signal to <1%.     

Near-grain-boundary characterization by atomic force microscopy

Characterization of near-grain boundary is carried out by atomic force microscopy (AFM). It has been observed to be the most suitable technique owing to its capability to investigate the surface at high resolution. Commercial purity-grade nickel processed under different conditions, viz., (i) cold-rolled and annealed and (ii) thermally etched condition without cold rolling, is considered in the present study. AFM crystallographic data match well with the standard data. Hence, it establishes two grain-boundary relations viz., plane matching and coincidence site lattice (CSL Σ=9) relation for the two different sample conditions.     

Combined low-temperature scanning tunneling/atomic force microscope for atomic resolution imaging and site-specific force spectroscopy

We present the design and first results of a low-temperature, ultrahigh vacuum scanning probe microscope enabling atomic resolution imaging in both scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) modes. A tuning-fork-based sensor provides flexibility in selecting probe tip materials, which can be either metallic or nonmetallic. When choosing a conducting tip and sample, simultaneous STM/NC-AFM data acquisition is possible. Noticeable characteristics that distinguish this setup from similar systems providing simultaneous STM/NC-AFM capabilities are its combination of relative compactness (on-top bath cryostat needs no pit), in situ exchange of tip and sample at low temperatures, short turnaround times, modest helium consumption, and unrestricted access from dedicated flanges. The latter permits not only the optical surveillance of the tip during approach but also the direct deposition of molecules or atoms on either tip or sample while they remain cold. Atomic corrugations as low as 1 pm could successfully be resolved. In addition, lateral drifts rates of below 15 pm/h allow long-term data acquisition series and the recording of site-specific spectroscopy maps. Results obtained on Cu(111) and graphite illustrate the microscope's performance.     

Mean atomic number and backscattered electron coefficient calculations for some materials with low mean atomic number

In modelling electron backscattering from solids using Monte Carlo simulations, knowledge of mean atomic number, mean atomic weight, and density of the bulk material are required. We studied four different ways in common useforthe calculation of mean atomic number. An alternative and improved approach is to calculate the mean backscattered electron (BSE) coefficient, η , from a knowledge of the elemental composition and values of η for the elements. Again, we studied a number of formulae suggested for this averaging process. As it is not possible to measure η directly for a number of elements, the method used to interpolate between elements with known η was also examined. In addition, we obtained experimental backscattering relationships for topography-free samples of poly (methylmethacrylate) (PMMA), carbon, aluminium, and a series of novel halogenated resins, all solids with relatively low mean atomic numbers, and calcified tissues. None of the methods for determining mean atomic number placed the materials of interest in the correct sequence of their experimentally determined BSE peaks: the data differed widely between the individual methods. The averaged BSE coefficient calculated by the Castaing formula gave the best agreement with the experimentally derived data.     

Channelling effects in atomic resolution STEM

A Bloch wave theory for incoherent scattering of an incident plane wave has proved successful in predicting the fine detail in 2-D zone axis channelling patterns formed by ADF, BSE and characteristic X-ray detection in beam rocking mode. A previously published example of polarity determination of GaAs by channelling contrast is compared with simulations in order to illustrate the applicability of the theory. Modification of boundary conditions for a focused coherent probe allows lattice-resolution incoherent contrast based on ADF and EELS detection as well as X-ray emissions to be catered for within a similar theoretical framework. Mixed dynamic form factors constitute an integral part of this theory, where quantum-mechanical phase is a core issue. Simulations of lattice-resolution ADF and EELS are discussed with reference to various zone axis projections of GaAs. Issues of single versus double channelling conditions, and local versus nonlocal interactions, are discussed in relation to X-ray, ADF and EELS detection.