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《材料导报》2020,(3)
微通道板(MCP)是光通讯和光电子技术领域实现电子倍增和信号放大的核心器件,其性能提升主要包括提高增益、延长寿命和降低暗计数。目前国内外普遍使用的商品化微通道板仍是基于传统铅硅酸盐玻璃经氢还原工艺制备的。尽管经过四代玻璃组分和制备工艺优化,MCP增益可达10~3,寿命为0.3 C/cm~2,暗计数为0.25 events/(s·cm~2),但由于玻璃组分和复杂制备工艺的限制,其离子反馈、背景噪声很难进一步降低,增益也无法大幅提升。鉴于此,近10年来科研人员提出并完善了新的解决方案——利用原子层沉积(ALD)技术,在硼硅酸盐玻璃基板孔内制备导电层和二次电子发射层等功能层,从而获得具有导电和电子倍增能力的微通道板。这种新型原子层沉积微通道板(ALD-MCP)有效避免了基板玻璃材料对其性能优化的制约,实现了基板材料和功能材料的独立设计,能够显著提高微通道板的综合性能。经过一系列尝试,国际上已开发出性能远优于传统MCP的ALD功能层:以Al_2O_3/ZnO、Al_2O_3/W或Al_2O_3/Mo为导电层,MgO或Al_2O_3为二次电子发射层的ALD-MCP增益已达10~4,暗计数降低至0.078 events/(s·cm~2),寿命提升至7 C/cm~2,但是其性能稳定性仍有待进一步提高。此外,还需要在提高沉积效率、优化调控功能层性能等方面进一步深入研究。本文从功能层的组成和微通道板的性能两方面归纳、梳理了利用原子层沉积技术制备微通道板的国内外研究情况,并总结了目前研究中存在的不足,展望了未来发展趋势。 相似文献
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ZnO薄膜中可见光的发射与缺陷有关,为了研究ZnO薄膜中与Zn原子缺陷相关的发光特性,将不同Zn缓冲层厚度的ZnO薄膜沉积在Si衬底上,且所有样品在400℃下真空中退火1 h,采用X射线衍射谱(XRD)、吸收谱和光致发光谱(PL)表征了样品的晶体结构和光学特性。结果表明,随着Zn缓冲层溅射时间的增加,ZnO薄膜中的紫光峰向长波段发生了红移,且所有的发光峰强度逐渐增加;缓冲层和真空中退火都使得样品中有过量的Zn原子缺陷出现,薄膜中所有的发光峰与Zn原子缺陷相关。 相似文献
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间隙密封技术是自由活塞斯特林发动机的一项关键技术,间隙密封避免了摩擦损耗,不需要润滑,对自由活塞斯特林发动机整机性能的提高起到了重要的作用。本文建立了自由活塞斯特林发动机间隙密封双边运动的一维层流模型,结合施密特等温分析法,对一台输出功率为100 W的自由活塞斯特林发动机计算了工作腔与缓冲腔之间的泄漏率曲线和单个循环工作腔向缓冲腔泄漏的泄漏量,并比较了不同间隙宽度情况下泄漏损失所占的比重,得到了最大允许的密封间隙宽度。同时,建立带有进出口的二维模型,运用Fluent进行了数值模拟,并与一维层流模型计算结果进行对比,得出二者泄漏率基本一致的结果,但由于间隙流动处进出口体积骤变的存在,二维模型数值模拟结果泄漏率略低于一维层流模型,更接近实际情况。 相似文献
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Si(111)衬底上多层石墨烯薄膜的外延生长 总被引:1,自引:0,他引:1
利用固源分子束外延(SSMBE)技术, 在Si(111)衬底上沉积碳原子外延生长石墨烯薄膜, 通过反射式高能电子衍射(RHEED)、红外吸收谱(FTIR)、拉曼光谱(RAMAN)和X射线吸收精细结构谱(NEXAFS)等手段对不同衬底温度(400、600、700、800℃)生长的薄膜进行结构表征. RAMAN和NEXAFS结果表明: 在800℃下制备的薄膜具有石墨烯的特征, 而 400、600和700℃生长的样品为非晶或多晶碳薄膜. RHEED和FTIR结果表明, 沉积温度在600℃以下时C原子和衬底Si原子没有成键, 而衬底温度提升到700℃以上, 沉积的C原子会先和衬底Si原子反应形成SiC缓冲层, 且在800℃沉积时缓冲层质量较好. 因此在Si衬底上制备石墨烯薄膜需要较高的衬底温度和高质量的SiC缓冲层. 相似文献
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基于NiFeCo/Cu多层膜巨磁电阻效应的磁微球检测 总被引:1,自引:0,他引:1
分析了应用于磁性生物检测的GMR传感器的工作原理.直流磁控溅射法制备了Ni65Fe15CO20/Cu多层膜,研究了室温下多层膜的GMR效应对缓冲层(NiFeCo)厚度、间隔层(Cu)厚度及铁磁层(NiFeCo)厚度等参数的依赖关系,得到了GMR值达8.8%的多层膜样品:缓冲层(NiFeCo)5nm,间隔层(Cu)2.4nm,铁磁层(NiFeCo)1.6nm,且饱和场低、磁滞小、灵敏度较高,符合磁性生物检测技术的要求.制备了基于优化参数NiFeCo/Cu多层膜的GMR传感器,对器件的性能进行了测试,结果表明所制备的GMR传感器能够检测磁微球. 相似文献
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Coherent population trapping (CPT) on 87Rb atoms in neon atmosphere has been studied in small-size glass absorption cells under conditions of pumping with narrow-band laser radiation at the D2 line of the main doublet. Parameters of the absorption signal have been measured in 3-mm-diameter cells at buffer gas (Ne) pressures varied within 200–400 Torr, cell temperatures within 65–120°C, and pumping radiation power densities within 30–400 μW/cm2. Optimum values of the buffer gas pressures, cell temperature, and pumping power are determined at which the short-term instability of the resonance line is at minimum. Orientational shifts of the CPT resonance signal in gas-filled cells and small-size cells with antirelaxation coating have been compared. 相似文献
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Gerginov V. Knappe S. Shah V. Hollberg L. Kitching J. 《IEEE transactions on instrumentation and measurement》2008,57(7):1357-1361
We demonstrate a new technique for the suppression of noise associated with the laser source in atomic clocks based on coherent population trapping (CPT). The technique uses differential detection of the transmission of linearly and circularly polarized beams that propagate through different parts of a single rubidium vapor cell filled with a buffer gas mixture. The common-mode noise associated with the laser frequency and amplitude noise is suppressed by the differential detection of the two laser beams. The CPT signal, which is present only in the circularly polarized laser beam, is unaffected. The implementation of the technique requires only a change of the polarization of part of the laser beam and an additional photodiode. The technique is simple and applicable to CPT frequency references where a major source of noise is the laser, such as compact and chip-scale devices. 相似文献
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The successful application of micro-sensing chips based on ion-sensitive field effect transistor principles depends on preventing the penetration of electrolyte into the interface between the encapsulation polymer and the insulating layer. This study employs a capacitance-voltage (C-V) technique to evaluate the adhesion and hermeticity of the polymer-substrate interface in a liquid environment. Three-layered structures simulating micro-sensing chips were fabricated for the evaluation. Each three-layered structure comprises an upper epoxy layer (with or without a window opening), a middle dielectric layer, and a lower Si wafer substrate. Equivalent circuits were established to explain the C-V characteristics of the three-layered structures. The results show that by applying the C-V technique and using an appropriate equivalent circuit, the adhesion and hermeticity between the encapsulating epoxy layer and the insulating layer can be evaluated. 相似文献
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Iyanu G. He Wang Camparo J. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(6):1139-1144
Although atomic clocks have very low levels of frequency instability, they are nonetheless sensitive (albeit slightly) to various environmental parameters, including temperature, power supply voltage, and dc magnetic fields. In the terrestrial environment, however, atmospheric pressure (i.e., the air's molecular density) is not generally included in this list, because the air's density variations near the surface of the Earth will typically have a negligible effect on the clock's performance. The situation is different, however, for clocks onboard satellites like Galileo, where manufacturing and testing are done at atmospheric pressure, while operation is in vacuum. The pressure sensitivity of atomic clocks, in particular vapor-cell atomic clocks, can therefore be of significance. Here, we discuss some of the ways in which changes in atmospheric pressure affect vapor-cell atomic clocks, and we demonstrate that, for one device, the pressure-sensitivity traces back to a pressure-induced change in the temperature of the clock's filter and resonance cells. 相似文献
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戚长政 《真空科学与技术学报》2003,23(2):143-146
本文建立了CPT管壳有限元计算模型 ,以计算的机械应力和热应力为依据 ,分析了CPT管壳在排气炉内炸裂的原因 ,为合理制定在排气过程中升、降温工艺路线 ,正确设计CPT管壳等提供了参考依据 相似文献
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Adsorptive removal of chlorophenols from aqueous solution by low cost adsorbent--Kinetics and isotherm analysis 总被引:1,自引:0,他引:1
Adsorptive removal of parachlorophenol (PCP) and 2,4,6-trichlorophenol (TCP) from aqueous solutions by activated carbon prepared from coconut shell was studied and compared with activated carbon of commercial grade (CAC). Various chemical agents in different concentrations were used (KOH, NaOH, CaCO(3), H(3)PO(4) and ZnCl(2)) for the preparation of coconut shell activated carbon. The coconut shell activated carbon (CSAC) prepared using KOH as chemical agent showed high surface area and best adsorption capacity and was chosen for further studies. Batch adsorption studies were conducted to evaluate the effect of various parameters such as pH, adsorbent dose, contact time and initial PCP and TCP concentration. Adsorption equilibrium reached earlier for CSAC than CAC for both PCP and TCP concentrations. Under optimized conditions the prepared activated carbon showed 99.9% and 99.8% removal efficiency for PCP and TCP, respectively, where as the commercially activated carbon had 97.7% and 95.5% removal for PCP and TCP, respectively, for a solution concentration of 50mg/L. Adsorption followed pseudo-second-order kinetics. The equilibrium adsorption data were analysed by Langmuir, Freundlich, Redlich-Peterson and Sips model using non-linear regression technique. Freundlich isotherms best fitted the data for adsorption equilibrium for both the compounds (PCP and TCP). Similarly, acidic pH was favorable for the adsorption of both PCP and TCP. Studies on pH effect and desorption revealed that chemisorption was involved in the adsorption process. The efficiency of the activated carbon prepared was also tested with real pulp and paper mill effluent. The removal efficiency using both the carbons were found highly satisfactory and was about 98.7% and 96.9% as phenol removal and 97.9% and 93.5% as AOX using CSAC and CAC, respectively. 相似文献
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Camparo J.C. Klimcak C.M. Herbulock S.J. 《IEEE transactions on instrumentation and measurement》2005,54(5):1873-1880
Over the past several years, anecdotal evidence has grown indicating that Rb vapor-cell frequency standards exhibit a long "frequency equilibration" period following activation (i.e., time constant /spl sim/10/sup 2/ days). Though this long equilibration period can have important implications for diverse timekeeping systems, the mechanism driving the behavior is not well understood and has been the subject of debate. In this paper, we investigate this phenomenon for a number of Rb vapor-cell clocks with the purpose of 1) establishing the validity of frequency equilibration as a generic vapor-cell atomic clock phenomenon and 2) obtaining characteristics of the equilibration process that can be used to constrain hypothesized frequency-equilibration mechanisms. Consistent with anecdotal evidence, results on three separate manufacturers' clocks indicate that frequency equilibration is a generic vapor-cell clock phenomenon, observable in both laboratory-based and space-based systems. However, the experimental data also casts doubt on the two mechanisms most often offered to explain frequency equilibration: helium permeation through the resonance cell's glass envelope, and the intensity-dependent light-shift effect. To help guide further research, we propose two alternate mechanisms for frequency equilibration: alkali surface diffusion on the resonance-cell and lamp walls, and the spectrum-dependent light-shift effect. 相似文献
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The effect of LiAl-layered double hydroxides (LiAl-LDHs) with 3D micro-nano structures on the early properties and hydration process of calcium sulphoaluminate cement (CSAC) clinker was investigated. Three LiAl layered double hydroxides (LiAl-LDHs) with different particle size were prepared through a facile solvothermal method. CSAC clinker incorporating LiAl-LDHs with constant water to cement radio were made and tested. The results indicate that a higher content of LiAl-LDHs resulted in a faster hydration rate, a shorter setting time and a higher early compressive strength. Besides, with the decrease of the particle size of LiAl-LDHs, the hydration rate was accelerated with corresponding increase in compressive strength. However, the influence of particle size of LiAl-LDHs on the setting time of CSAC clinker is not significant. Moreover, the addition of LiAl-LDHs did not result in a new phase formed, but increased the quantity of hydration products providing higher compressive strength and shorter setting time. 相似文献
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Camptothecin (CPT) is a topoisomerase I inhibitor that acts against a broad spectrum of cancers. Unfortunately clinical application of CPT is limited by insolubility, instability, and toxicity problems. To circumvent these delivery problems of CPT, we propose biocompatible, targeted sterically stabilized micelles (SSM) as nanocarriers for CPT (CPT-SSM). SSM composed of polyethylene glycol (PEGylated) phospholipids are attractive nanocarriers for CPT delivery because they are sufficiently small to extravasate through the leaky microvasculature of tumor and inflamed tissues for passive targeting. The purpose of this study was to develop a novel method of preparing CPT-SSM based on its pH dependent, reversible carboxylate-lactone conversion chemistry. CPT carboxylate was added to SSM at pH 5 that favored the formation of active but hydrophobic CPT lactone for spontaneous association with SSM. The kinetics of CPT conversion and CPT-SSM formation, and the effect of varying CPT-PEGylated phospholipid molar ratio on CPT-SSM properties and CPT solubilization were evaluated. CPT converted gradually from the carboxylate form to lactone, and CPT-SSM were formed after 12 h incubation. The mean size of CPT-SSM was approximately 14 nm. CPT solubilization (approximately 12 microg/ml) and other CPT-SSM micelle properties did not change significantly with increasing CPT to PEGylated hospholipid molar ratios using this novel method, unlike the coprecipitation/reconstitution technique previously reported. This reproducible CPT solubilization in SSM was attributed to avoidance of drug aggregate formation by this method. The advantages of our solvent pH change method to prepare CPT-SSM support further investigations of this approach to other hydrophobic drugs similar to CPT in chemistry and also CPT molecular solubilization in other nanocarriers. 相似文献
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高性能芯片级原子气室的制备是现阶段芯片级量子传感仪器研制急需解决的关键技术之一。为解决目前芯片级原子气室研制领域存在的碱金属定量填充难、气密性差等问题,开展了高气密性芯片级原子气室制备方法研究,利用微电子机械系统(MEMS)技术实现了芯片级原子气室的批量制备。采用深硅刻蚀技术制备硅气室腔,利用RbN3的光分解实现碱金属单质的制备及定量填充,采用阳极键合技术对原子气室进行两次硅片/玻璃键合封装,成功获得了以N2为缓冲气体的Rb碱金属原子气室。对所制备的原子气室进行键合强度、气密性、吸收光谱测试,结果表明原子气室的玻璃/硅片/玻璃键合强度均较高,其中B组原子气室的漏气率平均值为2.2×10-9 Pa![]()
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s-1,其气密性为目前行业内领先水平。最后从制备工艺上分析了两组原子气室的性能差异原因,为推动量子传感仪器的芯片级集成技术发展奠定重要基础。 相似文献