覆氧或氧离子轰击下固体表面二交正离子发射的研究

通过对离子轰击下固体表面电离过程重新考虑认为，在固体表面覆氧或氧离子轰击下除表面原子的直接电离外，激发态双原子间电子交换和断键亦起重要作用，在此基础上修正了局部热力学平衡模型，得到了一个包含各类离子内配分函数、电离能、金属－氧原子键断键能以及表面金属原子与氧原子结合份数等参数决定的新电离几率分析表达式。应用该分析表达式解释了金属表面覆氧、氧离子轰击金属、化合物半导体表面二次离子发射中氧增强效应、充     

飞行时间二次离子质谱结合X-射线光电子能谱分析化学清洗后残留的表面有机物

用飞行时间二次离子质谱(TOF-SIMS)结合X射线光电子能谱,分析了用化学方法清洗后银片上残留的未知有机物.TOF-SIMS与XIPS提供的互补的表面信息显示,中分子量以上的有机物主要是几种链长22～27碳原子、碳链饱和度很高的多酮类化合物,可能还有一些多酯类化合物.这些有机物中的C=O基团易于采取氧原子指向金属基体表面的取向,通过带部分负电荷的氧原子与金属基体镜像力的作用而增强粘附.     

一种新型二次离子质谱的一次离子源及其离子光学系统

本研究设计了一种新型用于二次离子质谱的一次离子源及其离子光学系统.通过此一次离子源,大气压下产生的一次离子可以被加速、聚焦并传输到位于真空条件下的样品表面并电离样品得到可供质谱仪分析的二次离子.通过理论模拟结合实验系统研究了此一次离子源的主要组成部分——离子光学系统的原理、结构和性能.以电喷雾电离源为例,成功地将大气压...     

合金电子谱定量分析中离子溅射修正因子的研究

离子溅射修正是电子谱(俄歇电子谱,AES和X射线光电子谱,XPS)、离子谱(二次离子质谱,SIMS和低能离子散射谱,ISS)定量分析中的关键问题之一。本文根据作者最近提出的离子轰击合金表面成分再分布关系,得到了表面分析中离子溅射修正因子的分析表达式,总结了近十多年来合金离子溅射修正因子的一些较普遍的实验结果,用本文报道的计算关系较好地解释了这些实验结果。讨论了溅射修正因子受轰击离子参数(入射角、能量)、组分浓度等因素的影响。同时用本文给出的分析计算关系讨论了择优溅射、离子辐照诱导偏析和增强扩散效应对溅射修正因子的影响。     

Cr-AlN界面的二次离子质谱研究

采用电子束蒸发的方法在２００℃抛光的氮化铝（ＡｌＮ）陶瓷衬底上淀积２００ｎｍ的Ｃｒ膜，并在高真空中退火。利用ＭＣｓ＋－ＳＩＭＳ技术（在Ｃｓ＋一次离子轰击下检测ＭＣｓ＋型二次离子）对样品进行了深度剖析，给出了界面组分分布随退火温度与时间的变化关系。结果表明，ＭＣｓ＋－ＳＩＭＳ技术是研究金属－陶瓷界面扩散与反应的有效方法。     

飞行时间二次离子质谱(TOF-SIMS)结合化学衍生法分析杂环新化合物的结构

飞行时间二次离子质谱(TOF-SIMS)分析了难挥发的杂环新化合物咪唑啉硫氰酸盐及其三种衍生物,确认出很强的氢离化及银离化准分子离子峰,通过对各种衍生物谱图的对照分析,确认出较强的含有结构特征的碎片离子峰,并对该化合物在离子轰击下的裂解规律作了分析,支持了对该新化合物结构的鉴定.     

有机化合物对电感耦合等离子体质谱(ICP-MS)法测定食品中总砷的影响

目的 研究有机化合物对电感耦合等离子体质谱法（ICP-MS）测定食品中总砷的影响,分析总结一般规律,为食品中总砷的准确测定提供理论依据。方法 研究了甲醇和乙醇等14种有机化合物对ICP-MS测定砷的动能歧视模式（KED）信号值和动态反应模式（DRC）信号值的影响,通过分析各有机化合物的电离能、极性和溶解度等性质,推测其在ICP-MS测定体系中对砷响应信号值增敏或者抑制的可能机理。结果 有机化合物对ICP-MS的KED模式测定砷离子As+的信号值有增敏效应,对DRC模式测定氧化砷离子AsO+信号值的影响小于KED模式测定As+的信号值,而且过程也更为复杂。相反,氮氧化物会减弱As+和AsO+的信号值。锗、铟等内标元素原子与砷原子在等离子体中电离行为和灵敏度的差异,使得内标元素校准砷测定信号的漂移受到干扰。结论 推测有机化合物影响ICP-MS测定砷响应信号值的可能机理是：有机化合物和氮氧化物经电离或裂解之后分别生成碳离子或多原子碳离子和氮氧离子或氮氧基团,碳离子或多原子碳离子会与砷原子发生电荷转移反应,增强As+或AsO+的信号值,同时有机化合物也可能会与As+竞争氧气而降低AsO+的信号值,而具有强电负性的氮氧基团可能会与As+和AsO+发生电荷转移反应而减弱其信号值。有机化合物对砷的ICP-MS响应信号值的影响可能是受到有机化合物电离能、溶解度、极性和分子结构等综合因素的结果。     

氯碘甲烷在A带的光解动力学

利用离子速度影像方法结合共振增强多光子电离(REMPI)技术研究了氯碘甲烷在A带的光解机理. 从266和277 nm的I*(5p 2P1/2)和I(5p 2P3/2)离子速度影像获得了碎片的平动能分布和角度分布. I和I*的平动能分布呈单高斯型, 可用软自由基近似来解释. I和I*是在排斥的势能面上直接解离产生的. 实验得到的各向异性参数β证实分子受激发后主要产生3Q0态, 并且3Q0和1Q1态之间存在非绝热转移. 波长越短, 这种非绝热转移越强. 在235 nm附近, Cl和Cl*各向同性的离子影像说明氯原子来自于CH2ICl的二次解离过程, 即CH2ICl先解离产生CH2Cl自由基, 自由基再解离产生氯原子.     

β－烷氧羰乙基三氯化锡与水杨醛缩苯胺类Schif碱配合物的合成及表征

由β－烷氧羰乙基三氯化锡与水杨醛缩苯胺类Ｓｃｈｉｆ碱反应，合成了１３种新的有机锡－Ｓｃｈｉｆ碱配合物。经元素分析、ＩＲ、ＮＭＲ和ＴＧ－ＤＳＣ测定，对其结构进行了表征，配合物是通过酚羟基氧原子和锡原子的配键生成的。摩尔电导率测定结果表明，配合物均为非电解质。     

二次离子电池高比容量负极碳载体的研究进展

二次离子电池商业化负极石墨的比容量已接近理论比容量. 合金型负极和金属负极因具有高比容量而受到广泛关注, 但其循环性能差和安全性问题限制了实际应用, 据此提出载体设计策略. 碳材料具有来源广泛、 易于调控等特性, 常用作二次离子电池高比容量负极的载体. 本文从碳载体的孔结构、 比表面积、 电子导电率、 离子导电率、 杂原子掺杂和界面修饰的角度出发, 综述了其在硅基、 磷基、 锗基、 锡基负极以及金属锂、 钠等负极中的研究进展, 展望了碳载体的发展前景和方向.     

Determination of the ionization coefficient of carbon on an example of silicate glasses analysis by secondary ion mass spectrometry (SIMS)

A method is proposed for the quantitative estimation of the carbon ionization coefficient followed by the determination of its concentration in silicate glasses by secondary ion mass spectrometry (SIMS). The method is based on the calculation of the sputtering ratio of carbon from the surface of silicate glasses. The dependence of the ionization coefficient on the NBO/T parameter (ratio of the number of nonbridging oxygen atoms to the number tetrahedrally coordinated silicon and aluminum ions), corresponding to the structure and composition of the matrix, is shown. The dependences obtained are calibration graphs for the determination of the ionization coefficient and for the subsequent quantitative estimation of carbon in a silicate sample for a particular SIMS instrument and experimental conditions.     

Comparative studies of SIMS and SNMS analyses during the build up of sputter equilibrium under oxygen and rare gas ion bombardment

Sputtering of solid surfaces by using a focused ion beam is the basis for secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS). The ion bombardment initiates not only redistribution of sample atoms but also massive changes in the surface and near surface composition of the bombarded area due to the sputter process and implantation of the primary ions. Changes in the matrix-composition affects the secondary ion yields and therefore a steady state (sputter equilibrium) has to be reached before SIMS data can give quantifiable results. SNMS is much less affected by those yield effects and therefore a combination of SIMS and SNMS can establish a basis for interpretation of SIMS data before the steady state is reached. In order to determine the effects of primary ion incorporation, we applied different primary ion species successively to generate different equilibria. An oxygen ion beam oxidizes the sample surface and by using a rare gas primary ion (PI) this oxide can be removed and analyzed.     

Sputtering induced recombination of nitrogen isotopes on tungsten

Adsorbed isotopic mixtures of ¹⁴N₂ and ¹⁵N₂ at low coverages on polycrystalline tungsten have been used as model systems for studying sputtering induced recombination during secondary ion mass spectrometry (SIMS). Earlier studies have shown that N₂ is completely dissociated on a W surface at low coverage. Thermal desorption spectroscopy (TDS) has been employed here to confirm this fact; our results show that complete isotopic mixing occurs. Adsorbed nitrogen can be sputtered as both atoms and molecules and sputtering induced recombination of adsorbate atoms increases as primary ion energy increases. Sputtering induced recombination is detected through isotopic mixing in SIMS. The data show that the dominant mechanism for sputtering of dimers (N₂) is not direct emission from the surface but rather a sputtering induced recombination mechanism.     

Topography and field effects in secondary ion mass spectrometry Part II: insulating samples

A study is conducted on the effects of sample topography on the secondary ion mass spectrometry (SIMS) analysis of insulating samples, using poly(ethylene terephthalate) fibres (100 µm diameter) as a model system and simulations of the ion extraction field using finite element analysis. We focus on two significant issues: topographic field effects caused by the penetration of the extraction field into the sample, and the effect of charge compensation on the secondary ion images. Guidance is provided for setting the reflector voltage correctly for insulating fibres in reflectron SIMS instruments. The presence of the topographic sample distorts the extraction field, causing the secondary ions to be deflected laterally. This results in the severe loss of ion signals from the sides of the fibres because of the limited angular acceptance of the analyser. Strategies to reduce topographic field effects, including alternative sample mounting methods, are discussed. We also find that, in general, insulating samples are charged by the flood gun electrons resulting in a negative surface potential. This causes large variations in the SIMS images depending on the electron current, electron energy, raster mode and secondary ion polarity. Recommendations are given for analysts to obtain more reproducible images and reduce the effect of differential electron charging, for example by using a lower electron flood beam energy. © 2011 Crown copyright.     

Diagnostic and analytical study of post ablation ionization of neutral atoms of major and minor constituents from a low alloy steel

Post ablation ionization (PAI) of neutral atoms from a low alloy steel has been investigated using non-resonant laser ionization in a time-of-flight mass spectrometer. By varying the delay between the ablation and ionization lasers, the velocity distributions of the Ti, V, Cr, Mn and Fe atoms have been determined simultaneously. These distributions have been recorded as a function of ablation laser fluence. The half-range Maxwell-Boltzmann velocity distribution has been used to fit the data and different characteristic temperatures have been determined for the various elements in the sample. The quantitative capability of this method for bulk and surface analysis has been evaluated by calculating the relative sensitivity factors (RSFs) for the various constituent elements. The RSFs for all of the elements are seen to be highly dependent on the delay between the ablating and ionizing lasers. This dependence was reduced by integrating the temporal dependent ion yield, leading to a significant improvement in the calculated RSF values. It was also found that the RSFs were not highly dependent on the power density of the ablation laser beam.     

Oxygen diffusion in nanocrystalline yttria-stabilized zirconia: the effect of grain boundaries

The transport of oxygen in dense samples of yttria-stabilized zirconia (YSZ), of average grain size d approximately 50 nm, has been studied by means of 18O/16O exchange annealing and secondary ion mass spectrometry (SIMS). Oxygen diffusion coefficients (D*) and oxygen surface exchange coefficients (k*) were measured for temperatures 673相似文献   

Oxygen adsorption on small PtNi nanoalloys

The adsorption of an oxygen molecule on nanoclusters of Pt and PtNi, in the size range between 13 and 55 atoms, has been studied using first-principle simulations. The structures have been obtained as a function of size and chemical composition of the clusters by means of the parallel excitable-walkers basin hopping method. O(2) preferentially adsorbs along the edge between two (111) facets due to a massive distortion of the Pt-Pt bond length. This bond elongation favours the adsorption in such a way that the binding energy of oxygen on a pure 55-atom cluster is still twice the value on the clean Pt(111). On the other hand, on 55-Pt(shell)Ni(core) nanoparticles, the O(2) binding energy is slightly lower than on Pt(111), because nickel core inhibits the stretching of the Pt-bond because of their size mismatch. However, as soon as its concentration is increased, Ni appears at the surface and its oxyphilic nature contributes to bind the oxygen molecule stronger.     

Quantitative analysis of films by ion microbeam methods. II: SIMS

The performance indicators for a quantitative analysis (random and systematic uncertainties) are defined, and their origin in SIMS (secondary ion mass spectrometry) is discussed. The different methods for quantitative SIMS analysis: calibration curve approach, implanted standard method, relative sensitivity factor (RSF) method, are discussed. Examples are given for successful quantitative SIMS analyses of epilayers, implanted depth profiles and interface (IF) impurity distribution. In conclusion, a comparison is made between SIMS and other advanced techniques for thin film analysis.     

The mass spectrometric fragmentation of n-heptane

The electron impact fragmentation of n-heptane has been investigated using ¹³C labelled derivatives. A mechanism is proposed for the loss of alkyl radicals where the cleavage of a C? C bond is coupled with the rearrangement of a hydrogen atom, thus yielding a secondary alkyl ion that eventually fragments further by a subsequent loss of olefin. For alkyl ions with less than six carbon atoms this consecutive pathway is in competition with formation directly from the molecular ion. The consecutive pathway contributes about 15% to the intensity of the alkyl ions with four and five carbon atoms and 80% for smaller ions. The electron energy dependence was studied.