Differential sample charging in ESCA

An ESCA study of some “intermediate” conductors demonstrates a differential charging effect when the sample block is biased. The variation of the intensity and width of the peak from silver 3d electrons in silver iodide is used to show how the flux of the beam, the conductivity of the sample, the size and polarity of the bias and the grid mounting alter the effect. The results suggest that in unbiased samples differential sample charging contributes significantly to the width of peaks.     

毫米级栅型电场分布FEP薄膜驻极体的制备及其电荷存储性能研究

采用电晕注极和热注极技术, 在厚度为25 μm的氟化乙丙烯共聚物(FEP)表面制备了宽度为2 mm和3 mm的具有栅型电场分布的驻极体, 研究了注极温度和电极宽度对其电荷存储性能的影响. 样品注极后经150天的存储, 栅型电场分布变得清晰而有规律, 覆盖铝电极区电位已衰减至接近零, 未覆盖铝电极区仍保持高电位; 对电极宽度为2 mm和3 mm的样品, 覆盖铝电极区与未覆盖铝电极区的表面电位差分别为110 V和130 V(电场强度差分别为44 kV/cm和52 kV/cm). 表面电位跟踪测试结果表明: 电晕注极样品初始表面电位高于热注极样品; 在相同的注极方法下, 注极温度越高初始表面电位越高, 电极宽度越小初始表面电位越低. 依据电晕注极和热注极原理对实验结果的分析表明, FEP和金属铝在电荷存储性能上的差异是FEP表面蒸镀铝电极后能获得栅型电场分布的原因所在.     

About the charging effect in X-ray photoelectron spectrometry

Investigations of X-ray photoelectron spectra from electrically nonconductive samples need corrections for the charging effect. This effect is qualitatively well established in the literature but has not been analyzed systematically up to now. Three main contributions determine the resulting mean charging potential at the sample surface: electron emission from the sample, electrons impinging on the sample from the X-ray tube window, and finally electron conduction in the sample surface.     

电子辐照下聚合物介质内部放电模型研究

空间电子辐照环境中,聚合物介质充放电现象是威胁航天器安全的重要因素. 传统航天器介质充放电模型仅能分析材料充电过程,缺乏对放电前后介质电位残余情况与放电脉冲强弱的评估. 本文通过引入介质放电电导率,在数值积分 充电模型基础上建立同时描述航天器介质内部充电和放电过程的新模型,并将模型计算结果与实验数据进行比较,验证了所构建的模型. 模型分析结果表明,聚合物介质放电残余电位与放电电流脉冲宽度随着样品电阻率的增加而增大,放电电流强度随着临界电场强度和充电时间的增加而增强,其增幅随着辐照电子束流强度的增加而增大. 关键词： 放电模型 内部放电 电子辐照 航天器介质     

Spatial structure of an incompressible quantum Hall strip

The incompressible quantum Hall strip is sensitive to charging of localized states in the cyclotron gap. We study the effect of localized states by a density functional approach and find electron density and the strip width as a function of the density of states in the gap. Another important effect is electron exchange. By using a model density functional which accounts for negative compressibility of the QH state, we find electron density around the strip. At large exchange, the density profile becomes nonmonotonic. Both effects, localized states and exchange, lead to a substantial increase of the strip width.     

液相基底温度对沉积银原子及其团簇凝聚过程的影响

研究了沉积银原子及其团簇在液相基底(硅油)表面的凝聚过程随基底温度的变化关系.实验结果表明:当硅油基底温度升高时,沉积银原子及其团簇的凝聚过程仍基本符合二阶段生长模型; 样品具有明显的边缘效应,在样品中心区域,凝聚体的覆盖率比边缘的相应值小,样品中心区域的凝聚体覆盖率先随薄膜名义厚度的增加迅速增大,然后逐渐趋于饱和,覆盖率趋于饱和时的膜厚值随基底温度的升高而降低; 对于一定的薄膜名义厚度,硅油基底温度越高,中心区域的凝聚体覆盖率越小.银原子凝聚体的分枝平均长度随基底温度的演化过程也具有类似的规律.对沉积银 关键词： 薄膜 液相基底 分枝状凝聚体 生长模型     

电子辐照聚合物带电特性多参数共同作用的数值模拟

电子辐照聚合物样品的带电特性是扫描电子显微镜成像、电子束探针微分析以及空间器件辐照效应等领域的一个重要研究课题. 通过建立基于蒙特卡罗方法的电子散射和时域有限差分法的电子输运的数值模型, 并采用高效的多线程并行计算, 模拟了电子非透射辐照聚合物样品的带电特性, 得到了带电稳态下的样品底部泄漏电流密度、表面负电位以及样品总电荷密度等带电特征量受入射电子能量、入射电流密度、样品材料的电子迁移率、样品厚度等相关参数共同作用的影响. 结果表明, 一个参数的变化使表面负电位增强时, 其他参数对负电位的影响将增强. 样品的带电稳态特征量在同一个电流平衡的模式下受参数影响的变化是单调的. 当电流平衡模式发生变化时, 如在入射电子能量较低的条件下, 样品内部的总电荷量会随着样品厚度的增大而先增加后减小, 出现局部极大值. 样品底部的泄漏电流密度随着入射电流密度的增大而近线性成比例地增大. 研究结果对于揭示电子辐照聚合物的带电规律及微观机理、预测不同条件下的样品带电状态具有重要科学意义.     

Nonlinear refraction and nonlinear absorption of silver aggregates in a polymeric matrix

The nonlinear optical characteristics of silver aggregates in a polymeric matrix are studied by the Z-scan method at the wavelength λ = 1064 nm. The nonlinear refractive index and the third-order nonlinear susceptibility of a sample with silver aggregates are measured. It is shown that the nonlinear refraction in the sample is related to the Kerr effect. The character of the nonlinear absorption process is discussed.     

Application of differential charging in XPS for structural study of Langmuir-Blodgett films

Differential charging in XPS was recently shown to be a novel technique for studying in-depth structural information of discrete cadmium layers in Langmuir-Blodgett?(LB) multilayer films. Here we report structural modification in multilayer LB films after sulfidation using differential charging in angle-dependent XPS that are not observable by the x-ray reflectivity technique. An AFM study suggests less modification in compact LB films in comparison to the non-compact ones. The differential charging in the LB multilayers changes after sulfidation due to the formation of cadmium sulfide nanostructures in the cadmium arachidate LB matrix, which was reflected prominently in the differential charging of Cd?3d(5/2) XPS peaks. It was found that, even after sulfidation, the compact multilayer LB films were differentially charged in the out-of-plane (in-depth) direction, whereas this kind of differential charging was not apparent in rough and non-compact films. Our results clearly indicate that for LB films with compact structure a partial layered structure survives the impact of particle formation, whereas for non-compact films the modification is large and no specific conclusion could be drawn. While x-ray reflectivity cannot provide specific information about the internal structure of the post-sulfidation films it shows that the total thickness of the films reduces in all cases.     

侧边抛磨单模光纤表面等离子体传感器的设计和优化

光纤表面等离子体共振传感器具有体积小、抗电磁干扰,可以实现在线实时远距离检测的优点。为提高传感器的性能,建立了侧边抛磨光纤表面等离子体共振传感的物理模型,分别研究了侧边抛磨光纤的剩余厚度、银膜层的厚度对传感器的灵敏度、共振峰的深度和半高全宽等的影响。结果表明：光纤剩余厚度越小,表面等离子体共振现象越强;随银膜层的厚度增大,共振峰的宽度变宽,而传感器的灵敏度呈现非单调变化。通过综合表面等离子体共振传感器的折射率传感灵敏度和共振峰半高全宽,提出了质量因数作为传感器的优化指标,并最终得到最优化的设计方案为光纤剩余厚度为66.5 μm,银膜的厚度为50 nm,此时质量因数达到98.67。     

用于诊断纳秒脉冲电流的微分环现场标定技术

分析了用于纳秒脉冲电流测量的微分环标定难点,提出微分环现场标定方法。通过脉冲形成线脉冲充电以解决微分环标定中信噪比较低、可信度较差等问题;分析了脉冲形成线充电时间、充电电压及脉冲形成开关击穿电压等回路参数对标定结果的影响。基于闪光二号加速器,对测量二极管电流的微分环进行了现场标定,前级隔离开关平均击穿电压为25 kV时,微分环标定回路电流达到1.3 kA,微分环灵敏度为9.311010,方差为0.151010。     

Sur la fiabilité du pic 1s du carbone de contamination comme étalon interne d'énergie dans les spectres de photoélectrons

The hydrocarbon contamination of an AEI ES 100 spectrometer has been studied in order to determine the reliability of the C 1s line as a standard in X-ray photoelectron spectra of non conducting solids. With alumina samples, it is shown that the contamination layer of this non ultra-high vacuum spectrometer is a suitable standard of energy for the correction of the charging effect and that it gives relative measurements with an accuracy of ± 0.2 eV when the sample temperature is varied from ?180°C to 200dgC or the sample holder is biased between ?10 and 10 V. About 75 spectra were recorded with powdered alumina compressed into a copper grid and the standard deviations of the corrected kinetic energies of the Al 2p and O 1s photoelectrons are respectively 0.09 and 0.06 eV.No effects of the X-ray tube current and the irradiation time are detected. The charging effect increases with the sample temperature (+0.6 eV from ?180 to 200°C).     

Excimer laser-assisted annealing of silicate glass with ion-synthesized silver nanoparticles

The effect of KrF excimer laser radiation on a composite layer consisting of sodium-potassium silicate glass with silver nanoparticles is studied as a function of the number of laser nanosecond pulses. The silver nanoparticles are synthesized by ion implantation. The measured optical absorption of the composite layer demonstrates that the silver nanoparticle size decreases monotonically as the number of laser pulses increases. Rutherford backscattering shows that laser annealing is accompanied by silver diffusion into the bulk of the glass and partial metal evaporation from the sample surface. The detected decrease in the silver nanoparticle size is discussed in terms of simultaneous melting of silver nanoparticles and the glass matrix due to the absorption of laser radiation.     

New possibilities for tuning ultrathin cobalt film magnetic properties by a noble metal overlayer

Complementary multiscale magneto-optical studies based on the polar Kerr effect are carried out on an ultrathin cobalt wedge covered with a silver wedge and subsequently with the Au thick layer. A few monolayers of Ag are found to have a substantial effect on magnetic anisotropy, the coercivity field, and Kerr rotation. The silver overlayer thickness-driven magnetic reorientation from easy axis to easy plane generates a new type of 90 degrees magnetic wall for cobalt thicknesses between 1.3 and 1.8 nm. The tuning of the wall width in a wide range is possible. Tailoring of the overlayer structure can be used for ultrathin film magnetic patterning.     

大面积染料敏化太阳电池的串联阻抗特性研究

在电子扩散微分方程的基础上,研究了染料敏化太阳电池光生电流和光生电压随光照强度不同的变化关系.提出敏化太阳电池串联阻抗功率损耗模型,理论模拟了大面积电池（有效面积>1 cm²）光电转换效率随多孔薄膜有效面积宽度变化的曲线、透明导电基底膜与银栅极的比接触电阻以及在不同入射光强下银栅极体电阻对大面积染料敏化太阳电池光伏性能的影响.结果表明透明导电基底膜的方块电阻和银栅极体电阻对大面积染料敏化太阳电池的性能有很大影响,而这种影响随光强的减弱逐渐减小. 关键词： 染料敏化 太阳电池 串联阻抗 光电转换效率     

A new approach for preventing charging up of soft material samples by coating with conducting polymers in SIMS analysis

Dynamic secondary ion mass spectroscopy (SIMS) analysis of soft materials such as polymer or biomaterial is one of challenging subjects due to the charge up effect brought from the irradiation of a primary ion beam, hampering the collection of secondary ions. Conventional methods against the charging up are the electron beam irradiation for charge compensation and surface coating with metal, normally gold. Those methods require a compromise analytical condition, reducing the primary ion beam current to suppress the range of the charging, which degrading the performances of the SIMS analyses. We have proposed that a thicker conductive layer, capable of delocalizing the charge onto the surface, should be put on a soft insulator sample to avoid charging up. The depth profile of the hair sample coated wholly with a polythiophen-based conducting polymer was successfully measured in longer time without any charging up even in the maximum current of the oxygen primary ion beam (O₂⁺: 7.5 keV, 400 nA) or using an electron beam compensation system. Thus, the proposed method coating with a conductive organic polymer against the charging issue would be expected as a breakthrough on SIMS analysis.     

Three-dimensional numerical studies on the effect of the particle charge to mass ratio distribution in the electrostatic coating process

Charge to mass ratio is a crucial parameter that governs the behavior of particle trajectories in a charged cloud of particles. The complex nature of the charging process limits our ability to accurately determine the charging level when particles of varying size are present. Using a numerical approach, it is possible, however, to take into account predefined values for this parameter. In this paper, the average charge to mass ratio and the distribution of the charge to mass ratio in the coating of a flat target were systematically varied to demonstrate their effect on the motion of the charged particles. The results show that the transfer efficiency increases as the average charge to mass ratio increases. It was found that the transfer efficiency is a weak function of the average particle size in the range tested and that it increases as the width of the size distribution increases.     

银纳米粒子的SERS效应和SEF效应在微流控芯片光学检测中的应用

银纳米离子的SERS技术和SEF技术的信号检测灵敏度非常高,可以用在微流控芯片的定量分析中。为了提高微流控芯片光学检测技术的检测精度,提出一种在微通道中添加银纳米粒子来增强SYBR GreenⅠ拉曼和荧光信号的方法,并对该方法的原理和增强效果进行了研究。首先,利用准分子激光器在PMMA基板上直写刻蚀出宽200 μm、深68 μm的微通道,接着将制备的银前体溶液加入微通道,通过加热制备出表面增强拉曼（SERS）和表面增强荧光（SEF）基板,接下来对添加银纳米粒子前后的拉曼和荧光信号分别进行对比,进一步研究了微通道中不同浓度银纳米粒子对SYBR GREEN I的拉曼和荧光信号增强效果。添加银纳米粒子后,表面增强拉曼（SERS）实验的增强因子为3.5×10³,添加银纳米粒子的样品的荧光信号强度与不含银纳米粒子样品的荧光信号强度相比,约增加了1倍。结果表明,在微通道中检测SYBR Green I时通过增加银纳米粒子显著地增强了拉曼和荧光信号,这种方法可以用在以SYBR GreenⅠ做染料的微流控芯片检测技术中。     

样品表面银膜的粗糙度对钛酸钡微球成像性能的影响

研究了样品表面镀有不同表面粗糙度的银膜对钛酸钡（BaTiO₃ glass,BTG）微球成像效果的影响,发现当银膜表面的粗糙度（RMS）从3.23 nm增大到6.80 nm时,用直径为15 μm的BTG微球观察直径为250和580 nm的微球阵列,样品的成像范围增大.另外,BTG微球还可以清晰分辨原本不可分辨的直径为200 nm的微球阵列.结果表明,粗糙银膜引起的散射作用和表面等离激元波的局域场增强效应,使得更多物体的高频信息耦合进微球,提高了微球成像的分辨率和成像范围.     

基于PIC单片机的种子源设计

对种子源结构进行了优化设计,为了缩短充电时间,在现有的电容和DC变换器基础之上,选用单片机作为控制芯片,利用其脉冲宽度调制(PWM）输出功能产生用于控制DC变换器的线性电压。对单片机PWM输出转化为线性控制电压的性能以及控制DC变换器恒流充电的可行性开展了实验研究。实验结果表明,基于PIC单片机的种子源储能可以达到250 J,充电时间缩短到6 min以内,满足实验要求。