XPS分析中使用样品磁透镜引起的谱峰位移和峰形畸变

发现当使用Mg/Al双阳极和样品磁透镜进行非导电样品（或与样品托绝缘的导电样品）的X射线光电子能谱分析时，谱峰出现异常大的位移和谱形出现畸变；在同时使用电子中和枪时谱峰位移变小，当导电样品与样品托有良好的电接触时谱峰位移消失；作者提出这种异常大的位移来自样品荷电效应，后者是由于样品磁透镜的磁场与来自X射线枪A1窗的低能杂散电子发生了相互作用并使这些杂散电子不能到达样品表面起中和作用所致。     

磁透镜引起的氯化银谱峰异常位移及其在X射线光电子能谱成象分析中的应用

用X射线光电子能谱（XPS）分析了与样品托有良好电接触的银片及其上面的AgCl。观察到在使用样品磁透镜和非单色化X射线源的实验条件下不导电的AgCl的电子峰产生异常大的谱峰位移,还发现这种异常谱峰位移可以应用于XPS成象分析,以提高化学位移很小的元素化学态（如Ag^0和Ag^ )的XPS象的分辨能力。     

X光电子能谱分析中光电子峰和俄歇峰的干扰及消除

X光电子能谱(XPS)在分析多元素材料时,光电子峰可能受到其它元素俄歇谱的干扰.在AlKα激发CrZnSi合金样品时,光电子峰Cr2p和俄歇峰ZnLMM相互干扰,而换用双阳极中的MgKα源激发,虽可消除此相互干扰,但样品表面的Cls和Nls又会受到ZnLMM干扰.类似地,AlKα激发的GaN样品中Nls受俄歇峰GaLMM的严重干扰,而换用MgKα源激发时,Cls峰又受到的GaLMM的干扰.交替使用Mg/Al双阳极激发源,可改变XPS分析中的俄歇谱及其背景对光电子峰的干扰位置,并用未受干扰的峰互相校正2组谱图能量位置,以对样品谱峰作出正确的分析.     

单色化X射线对薄膜表面高分子降解行为的影响

采用聚甲基丙烯酸甲酯(PMMA)和苯乙烯-丙烯腈无规共聚物(SAN)薄膜体系, 在不同的实验温度下, 研究了单色化的X射线对其中一个组分(PMMA)降解行为的影响.     

荷电(±1)对二十面体X_(13)(X=Cr,Mn,Fe,Co)团簇的稳定性与磁性的影响

采用基于密度泛函理论的计算方法,对正二十面体金属X13(X=Cr,Mn,Fe,Co)中性和荷电团簇进行了全面的结构优化计算,研究了荷电对团簇的稳定性和磁性的影响.结果表明:荷负电能够使团簇的稳定性增强;荷电对不同团簇的原子间距离的影响不同;同时荷电对不同团簇磁性的影响也是不一样的,尤其是荷负电能够使Fe13和Co13团簇的磁性大大增强;荷电对不同团簇磁性的影响不是通过原子间距离的变化来实现的,而是受到原子内部电荷的转移和杂化程度的影响.     

二氧化硅接枝聚合磷酸胆碱/聚醚砜复合膜的制备及性能

以2-甲基丙烯酰氧基乙基磷酰胆碱(MPC)为两性离子单体,采用反向原子转移自由基聚合(RATRP)技术,在纳米二氧化硅表面接枝聚合磷酸胆碱,合成了两性离子材料二氧化硅-聚磷酸胆碱(SiO_2-PMPC);将其与聚醚砜(PES)共混,利用相转化方法制备了聚醚砜基杂化荷电复合膜(SiO_2-PMPC/PES).采用透射电子显微镜(TEM)、扫描电子显微镜(SEM)、傅里叶变换红外光谱(FTIR)、X射线光电子能谱(XPS)、接触角、原子力显微镜(AFM)及膜性能测试等研究了杂化荷电复合膜的结构与分离性能,考察了SiO_2-PMPC含量对杂化荷电复合膜性能的影响.研究结果表明,SiO_2-PMPC的添加有助于提高PES复合膜的亲水性;杂化荷电复合膜对染料活性黑5和活性绿19的截留率较高,分别达到82.6%和92.4%,而杂化荷电复合膜对无机盐的截留率则保持在8%以下,在保持较高水通量的同时,杂化荷电复合膜能够有效分离活性染料与无机盐.     

制样方法对固体粉末X射线光电子能谱测试结果的影响

为了得到准确且分辨率高的X射线光电子能谱(XPS)数据,采用不同制样方法对不同类型的导电、不导电和混合粉末的测试结果进行了研究. 从图谱半峰宽、是否有荷电、真实性、制样效率和数据处理等方面阐述不同制样方法对测试结果的影响. 试验结果表明,对于导电和不导电粉末,粘取制样略优于铟片制样,其中使用碳导电胶带制样效果更好. 对于混合样品,Scotch双面胶带粘样后的测试结果优于其他3种制样方式. 此外,铟片制样可作为数据处理时荷电校正的参考方法.     

动电法研究磺化聚醚砜纳滤膜界面电现象

采用动电法对表面具有功能基团解离的磺化聚醚砜纳滤膜(NTR-7450)界面电现象进行探索。其中,在Zeta电位测试过程中引入相关措施,例如采用电化学工作站测定体系总电导(膜体电导、膜表面电导和电解质溶液电导)和变化流道高度等,以便获得更为真实的Zeta电位,进而根据Gouy-Chapman双电层模型系统地考察了离子强度、阴离子种类(KCl,K2SO4和K3PO4)对膜表面荷电性能的影响。实验结果表明,在较低浓度(0.1～0.5mmol/L)电解质溶液中,磺酸基的解离是NTR-7450纳滤膜荷电的主要原因;而在较高浓度下(1.0～10mmol/L),NTR-7450纳滤膜荷电则是由特性吸附引起,并且膜体积电荷密度与电解质溶液浓度之间符合Freundlich吸附等温式:在KCl,K2SO4和K3PO4溶液中分别为:ln|X|(mmol/L)=2.3337+0.772lnC(mmol/L),ln|X|(mmol/L)=3.584+1.119lnC(mmol/L)和ln|X|(mmol/L)=2.988+1.067lnC(mmol/L)。     

低能离子散射谱分析中的荷电效应及中和作用

用低能离子散射谱（ISS）对比分析了与样品托有良好电接触的和与样品托绝比的金属银片，观察到荷电效应对ISS分析有严重影响。实验还表明在ISS分析时使用低能电子中和枪可以有效地消除荷电效应，还发现电子中和枪的使用对于惰性气体离子的中和作用无明显影响。     

样品高度对XPS测试的影响

采用Al靶微聚焦单色器光电子能谱仪进行XPS测试时,如果样品高度选择不好,会导致测得的光电子峰强度降低. 而对于一些电子结合能较高的元素,其光电子峰会变宽,有时出现双峰. 分析了该现象的原因是X射线光斑、电子中和枪中和区域以及光电子能量接收区域没有聚焦于同一点.     

X射线衍射仪新功能的开发及其应用

根据Ｘ射线衍射仪的结构特点,通过巧妙而简易的改装,增添了“同步照相”新功能。文中分析了开发新功能的可行性;列举了新功能在某些场合下,能使传统的照相法和现代的衍射仪法结合起来,取长补短的例子;指出新功能有助于提高分析测试水平,并可收到一机多用、节能高效的综合效果。     

Electrically Cooled SiLi Detectors for Application in X-Ray Equipment

The results of the development of electrically cooled SiLi detectors are presented for applications in X-ray equipment. The characteristics of such detectors compare well with those of the detectors cooled by liquid nitrogen, and to obtain these characteristics only 60 W of electric energy is needed instead of liquid nitrogen.     

Ab initio Hartree-Fock calculations of molecular X-ray intensities. Validity of one-center approximations

Ab initio Hartree-Fock calculations of relative X-ray transition probabilities for core hole states of N₂, CO, H₂O and NH₃ have been carried out and compared with the respective high-resolution soft X-ray spectra. The same one-determinental wavefunctions were employed for both initial and final states and the dependence of the X-ray transition moments on the choice of orbitals and of basis set parameters was investigated. In particular, orbitals optimized for a transition state were tested. The use of the one-center intensity model as a guide for the assignment of second row X-ray spectra was justified at bothab initio and semiempirical (CNDO) levels of approximation. The breakdown of the MO-picture for inner-valence electrons is demonstrated in the X-ray spectrum of N₂ and the analogy with the corresponding photoelectron bands is pointed out.     

X-ray fluorescence imaging with polycapillary X-ray optics

X-ray fluorescence spectrometry imaging is a powerful tool to provide information about the chemical composition and elemental distribution of a specimen. X-ray fluorescence spectrometry images were conventionally obtained by using a μ-X-ray fluorescence spectrometry spectrometer, which requires scanning a sample. Faster X-ray fluorescence spectrometry imaging would be achieved by eliminating the process of sample scanning. Thus, we developed an X-ray fluorescence spectrometry imaging instrument without sample scanning by using polycapillary X-ray optics, which had energy filter characteristics caused by the energy dependence of the total reflection phenomenon. In the present paper, we show that two independent straight polycapillary X-ray optics could be used as an energy filter of X-rays for X-ray fluorescence. Only low energy X-rays were detected when the angle between the two optical axes was increased slightly. Energy-selective X-ray fluorescence spectrometry images with projection mode were taken by using an X-ray CCD camera equipped with two polycapillary optics. It was shown that Fe Kα (6.40 keV) and Cu Kα (8.04 keV) could be discriminated for Fe and Cu foils.     

Near K-edge measurement of the X-ray attenuation coefficient of heavy elements using a tuneable X-ray source based on an electron LINAC

The X-ray attenuation coefficients of bismuth and of uranium were measured in the regions of 40–240 and 70–240 keV, respectively, using a tuneable hard X-ray source based on the linear electron accelerator at the University of Ghent. Results were compared with the semi-empirical values of Storm and Israel and to the theoretical values of Berger and Hubbell. We also propose a simple function for the attenuation coefficient in the vicinity of the K-edge for uranium and in an extended range of energy for bismuth. The set-up of the source at Ghent is described and the future improvements are explained.     

X-ray imaging using the radiation diffracted by polycrystalline materials

Imaging requires not only an area detector but also optics to relate the elements of the object to those of the detector. For X-rays optical elements based on reflection or refraction allowing the imaging of objects of several mm size are not available. Therefore, image formation like in the human eye cannot be achieved, but an approach realized in the eyes of insects where each facet has its own optics, has to be used. In the X-ray regime such a system can be realized by an arrangement of collimating tubes guiding the radiation from a region of the sample to the corresponding area of the detector and suppressing cross-fire from other regions.

Such an imaging system consisting of a microchannel plate in front of a CCD-detector has been installed on the 2Θ-arm of a 4-circle diffractometer at beamline G3 at HASYLAB, DESY. With this instrument, images as a function of one or more parameters can be collected. The structure of the data obtained in this way is distinct from those obtained by conventional diffraction techniques mostly yielding only one intensity value per scanning step and therefore requires different strategies for processing.     

A Probe of Valence and Conduction Band Electronic Structure of Lead Oxide Films for Photodetectors

We investigate how the electronic structure of amorphous lead oxide (a-PbO) films deposited on ITO substrate is changed after annealing at various temperatures. Both experimental soft X-ray spectroscopic and density functional theory (DFT) based computational techniques are used to explore the electronic structure of this material. X-ray emission, resonant X-ray inelastic scattering, and X-ray absorption spectroscopic techniques are employed to directly probe the valence and conduction bands. We discover that the films are very stable and remain amorphous when exposed to temperatures below 300 °C. An amorphous-to-polycrystalline (α-PbO phase) transformation occurs during annealing at 400 °C. At 500 °C, an alpha to beta phase change is observed. These structural modifications are accompanied by the band gap value changing from 1.4±0.2 eV to 2.0±0.2 eV upon annealing at 400 °C and to 2.6±0.2 eV upon annealing at 500 °C. A difference between surface and bulk structural properties is found for all samples annealed at 500 °C and above; these samples also exhibit an unexpected suppression of O : 2p density of states (DOS) near the bottom of the conduction band, whereas additional electronic states appear well within the valence band. This study provides a significant step forward to understanding the electronic properties of two polymorphic forms of PbO needed for optimization of this material for use in X-ray sensors.     

An ab initio investigation of the collective phenomena accompanying the core ionization in the radical NO

The influence of the reorganization effect of an electron system on potential energy curves of X-ray excited states of the radical nitric oxide has been investigated by the restricted Hartree-Fock method. A dominating role of this collective effect in forming fine vibrational structures in ESCA and X-ray K emission spectra of this radical has been shown by such calculations.     

Extended fine structure in characteristic X-ray fluorescence: A novel structural analysis method of condensed systems

An oscillation similar to that in extended X-ray absorption fine structure (EXAFS) is found in characteristic X-ray fluorescence spectra, originating from a quantum interference effect during the X-ray emission process in a solid. We observe the oscillating fine structure in the radiative Auger X-ray fluorescence spectra of aluminum metal. The Al-Al interatomic distances are successfully reproduced by the Fourier transform of the fine structure. Thus, the present method has the potential to become a convenient alternative to EXAFS measurement for light elements.     

On the use of polycapillary structures to improve laboratory Energy-Dispersive X-ray Diffractometry and Reflectometry

One of the major limits of the laboratory X-ray sources is represented by their low photon flux which induces many researchers to move to synchrotron beamlines. From this point of view, polycapillaries lenses represent an extraordinary tool to improve the performances of laboratory machine and, indeed, several models of polycapillary optics-based instruments, such as diffractometers, spectrometers etc., are currently available on the market. In this work, the application of polycapillary optics to a particular kind of non-commercial X-ray instruments, namely the Energy-Dispersive X-ray Diffractometers and Reflectometers, is proposed. The advantages and limits of the use of polycapillaries are discussed and the results of preliminary experiments are shown.