铝衰减膜表面氧化对软X光透过率的影响与修正

对用不同方法制备的软Ｘ光激光实验用的Ａｌ衰减膜样品,用Ａｕｇｅｒ电子能谱（ＡＥＳ）结合氩离子束刻蚀进行了组分的表面和深度分布分析,结果表明表面氧化层主要由Ａｌ２Ｏ３组成,氧化达到饱和时的氧化层厚度≈７．５ｎｍ。由于在软Ｘ光波段内,氧的吸收系数比铝大一个多数量级,这一氧化层对软Ｘ光透过率的影响甚大。将ＡＥＳ测试结果作为参数,使用公式Ｉ＝Ｉ０·ｅｘｐ［－μ（Ｅ）·（ρｄ）］对Ｘ光透过强度进行修正。同步辐射软Ｘ光对样品透过率的直接测量表明,对于透过率大于２０％的Ａｌ膜,直接测量结果与按修正公式计算的结果在最大偏差１１％范围内符合。     

现阶段模拟移动网发展方向探讨

随着数字移动通信的迅猛发展,第一代模拟移动通信已呈日趋萎缩的迹象。本文作者以泉州市的一些具体数据对模拟网的萎缩进行限说明,并着重指出,在现阶段应通过下调模拟网资费、作为市话网的延伸和补充,开展移动公用电话和租机业务以及缩减模拟网规模等手段,挖掘模拟网的潜力,使之发挥最大的经济效益。     

Engineering of Polyanion Type Cathode Materials for Sodium‐Ion Batteries: Toward Higher Energy/Power Density

The development of high energy/power density sodium‐ion batteries (SIBs) is still challenged by the high redox potential of Na/Na⁺ and large radius of Na⁺ ions, thus requiring extensive further improvement to, in particular, enhance the capacity and voltage of cathode materials. Among the various types of cathodes, the polyanion cathodes have emerged as the most pragmatic option due to their outstanding thermostability, unique inductive effect, and flexible structures. In this Review, a critical overview of the design principles and engineering strategies of polyanion cathodes that could have a pivotal role in developing high energy/power density SIBs are presented. Specifically, the engineering of polyanion cathode materials for higher voltage and specific capacity to increase energy density is discussed. The way in which morphology control, architectural design, and electrode processing have been developed to increase power density for SIBs is also analyzed. Finally, the remaining challenges and the future research direction of this field are presented.     

Ultrasoft Liquid Metal Elastomer Foams with Positive and Negative Piezopermittivity for Tactile Sensing

Soft, capacitive tactile (pressure) sensors are important for applications including human–machine interfaces, soft robots, and electronic skins. Such capacitors consist of two electrodes separated by a soft dielectric. Pressing the capacitor brings the electrodes closer together and thereby increases capacitance. Thus, sensitivity to a given force is maximized by using dielectric materials that are soft and have a high dielectric constant, yet such properties are often in conflict with each other. Here, a liquid metal elastomer foam (LMEF) is introduced that is extremely soft (elastic modulus 7.8 kPa), highly compressible (70% strain), and has a high permittivity. Compressing the LMEF displaces the air in the foam structure, increasing the permittivity over a large range (5.6–11.7). This is called “positive piezopermittivity.” Interestingly, it is discovered that the permittivity of such materials decreases (“negative piezopermittivity”) when compressed to large strain due to the geometric deformation of the liquid metal droplets. This mechanism is theoretically confirmed via electromagnetic theory, and finite element simulation. Using these materials, a soft tactile sensor with high sensitivity, high initial capacitance, and large capacitance change is demonstrated. In addition, a tactile sensor powered wirelessly (from 3 m away) with high power conversion efficiency (84%) is demonstrated.     

基于分段PID实现永磁同步电机快速启停控制技术的研究

扫描镜常用于获取空间光电信息,应用中对其快速启停和指向精度有较高的要求。针对永磁同步电机驱动扫描镜的运动方式,建立了电机Simulink仿真模型,并采用了三闭环矢量控制策略,提出了采用分段式比例积分微分(Proportion Integration Differentiation, PID)算法进行位置环控制的方法。结果表明,相较于传统的PID,分段式PID提高了系统的响应速度,同时控制精度和稳定性也有一定提升。     

悬臂式RF MEMS开关的设计与研制

介绍了一种制作在低阻硅(3～8Ω·cm)上的悬臂式RF MEMS开关.在Cr/ Au CPW共面波导上,金/Si Ox Ny/金三明治结构或电镀金作为悬置可动臂,静电受激作为开关机理.当开关处于“关断”态,其隔离度小于- 35 d B(2 0～4 0 GHz) ;阈值电压为13V ;开关处于“开通”态,插入损耗为4～7d B(1～10 GHz) ,反射损耗为- 15 d B.另外,还分析了开关的悬臂梁弯曲度与驱动电压的关系,并应用ANSYS软件对开关进行了电学、力学及耦合特性的计算机模拟     

Chemical natures and distributions of metal impurities in multicrystalline silicon materials

We present a comprehensive summary of our observations of metal‐rich particles in multicrystalline silicon (mc‐Si) solar cell materials from multiple vendors, including directionally‐solidified ingot‐grown, sheet, and ribbon, as well as multicrystalline float zone materials contaminated during growth. In each material, the elemental nature, chemical states, and distributions of metal‐rich particles are assessed by synchrotron‐based analytical x‐ray microprobe techniques. Certain universal physical principles appear to govern the behavior of metals in nearly all materials: (a) Two types of metal‐rich particles can be observed (metal silicide nanoprecipitates and metal‐rich inclusions up to tens of microns in size, frequently oxidized), (b) spatial distributions of individual elements strongly depend on their solubility and diffusivity, and (c) strong interactions exist between metals and certain types of structural defects. Differences in the distribution and elemental nature of metal contamination between different mc‐Si materials can largely be explained by variations in crystal growth parameters, structural defect types, and contamination sources. Copyright © 2006 John Wiley & Sons, Ltd.     

Modeling node mobility for reliable packet delivery in mobile ip networks

In this paper, we analyze node mobility for reliable packet delivery in mobile IP networks. In mobile IP, packets destined to roaming nodes are intercepted by their home agents and delivered via tunneling to their care of addresses (CoA). A mobile node may roam across multiple subnets. At each boundary crossing, a handoff is initiated such that the CoA is updated and a new tunnel is established. We consider both basic mobile IP handoff and smooth handoff. We find that reliable packet delivery in mobile IP networks can be modeled as a renewal process, because the retransmission over a new tunnel after each boundary crossing is independent of the previous history. We then derive the probability distribution of boundary crossings for each successful packet, based on which the packet reliable delivery time can be obtained. Our analytical model is derived based on a general distribution of residence time in a subnet and a general distribution of successful retransmission attempts in each subnet. The results can be readily applied to any distributions for both items. We also provide numerical examples to calculate the probability distribution of boundary crossings, and conduct simulations to validate our analytical results     

Comprehensive Study of Emitter-Ledge Thickness of InGaP/GaAs HBTs

A comprehensive study of emitter-ledge thickness of InGaP/GaAs heterojunction bipolar transistors (HBTs) has been undertaken. It is shown that the recombination rate and electron densities are drastically increased near the exposed base surface between the base contact and the emitter ledge. In contrast, the corresponding hole densities are decreased. If the emitter ledge is too thick, current will flow through the undepleted ledge, which increases the emitter-size effect. In contrast, if the emitter ledge is too thin, it may not effectively passivate the surface. Therefore, the thickness of the emitter ledge is a crucial issue and should be carefully considered. It is shown that, from simulated and experimental results, the optimum emitter-ledge thickness of InGaP/GaAs HBT is 100-200 Aring     

An investigation into the effects of probing and wire bonding stress on the reliability of BOAC

This work describes two types of low stress bonding over active circuit (BOAC) structures applying a finite element analysis. The advantage of improving the chip area utility of the BOAC design is approximately 150–180 μm for each dimension. A 0.13 μm 2 Mb high-speed SRAM with fluorinated silicate glass (FSG) low-k dielectric was combined with these two BOAC structures as the test vehicles to evaluate the impact of the probing and wire bonding stress on the reliability. Initially, a cantilevered probe card was applied to probe the BOAC pads using the typical and the worse probing conditions. Before and after the circuits probing (CP1 and CP2) the experimental results were compared, including the 2 Mb high-speed SRAM yield and wafer bit map data. The difference between the CP1 and CP2 results were negligible for all probing split cells. Next, the cross-section of the BOAC pad under the probing area was investigated following the worst probing condition. In addition, the BOAC pads evaluate the bondability, including the use of ball shear, wire pull and cratering tests. Moreover, all BOAC packaging samples underwent reliability tests, including HTOL, TCT, TST, and HTST. All the bondability and reliability tests passed the criteria for both proposed BOAC structures. Finally, the immunity level of both proposed BOAC pads, for ESD-HBM (human body mode) and ESD-MM (machine mode), differed slightly from the normal pads. No performance degradation was detected. Accordingly, this work shows that both proposed BOAC structures can be used to improve the active chip area utility or save the chip area.