Synchrotron radiation induced total reflection X-ray fluorescence of low Z elements on Si wafer surfaces at SSRL — comparison of excitation geometries and conditions

The analysis of low Z elements, like Na and Al at ultra trace levels (<10¹⁰ atoms/cm²) on Si wafer surfaces is required by the semiconductor industry. Synchrotron radiation induced total reflection X-ray fluorescence analysis (SR-TXRF) is a promising method to fulfill this task, if a special energy dispersive detector with an ultra thin window is used. Synchrotron radiation is the ideal excitation source for TXRF of low Z elements due to its intense, naturally collimated and linearly polarized radiation with a wide spectral range down to low energies even below 1 keV. TXRF offers some advantages for wafer surface analysis such as non-destructive analysis and mapping capabilities. Experiments have been performed at the Stanford Synchrotron Radiation Lab (SSRL) using Beamline 3-4 (BL 3-4), a bending magnet beamline using white (<3 keV) and monochromatic radiation, as well as Beamline 3-3 (BL 3-3), using a crystal monochromator as well as a multilayer monochromator. A comparison of excitation–detection geometry was performed, using a side-looking detector with a vertically positioned wafer as well as a down-looking detector with a horizontally arranged wafer. The advantages and disadvantages of the various geometrical and excitation conditions are presented and the results compared. Detection limits are in the 100-fg range for Na, as determined with droplet samples on Si wafer surfaces.     

Spectral Interference in Antimony Analysis with High Temperature Furnace Atomic Absorption

Abstract

Background correction in atomic absorption spectrophotometry using a high temperature furnace has a close relation to the chemical treatment and the detection limit. Conventionally used for this correction is the D₂ lamp method, but spectral interference is inevitable in this method because the spectral bandwidth of the light from the D₂ lamp after passing through a monochromator is as wide as 0.1 to 5 nm. In the analysis of Sb in lead alloy or in steel, there is spectral interference due to high concentration of elements such as Pb, Cu or Fe, in the matrix, so accurate measurement is impossible unless these elements are removed at the pretreatment stage.

In polarized analyte Zeeman atomic absorption spectrophotometry developed by the authors, the wavelength of the measuring beam is the same as that of the reference and they are identical in spectral line profile as well as in geometrical shape. They differ only in the direction of polarization. For these reasons, we found that there is no spectral interference like that recognized in the D₂ lamp correction technique. As a result, a direct analysis was done simply by dissolving gunmetal or steel in acid without removing the matrix elements Pb, Cu or Fe.     

Optimization of the spectral data processing in a LIBS simultaneous elemental analysis system

An instrumentation variation on laser-induced breakdown spectroscopy (LIBS) is described that allows simultaneous determination of all detectable elements using a multiple spectrograph and synchronized, multiple CCD spectral acquisition system. The system is particularly suited to the rapid analysis of heterogeneous materials such as coal and mineral ores. For the analysis of a heterogeneous material the acquisition cycle typically stores 1000 spectra for subsequent filtering and analysis. The incorporation of an effective data analysis methodology has been critical in achieving both accurate and reproducible results in the analysis of powders with the technology. Using naturally occurring gypsum as the optimization matrix, various data analysis techniques have been investigated including: using pulse-to-pulse internal standardisation; data filtering; and spectral deconvolution. The incorporation of normalization of the elemental emission to the total plasma emission intensity has been found to yield the single biggest improvement in accuracy and precision. Spectral deconvolution has been found to yield further improvement and is particularly relevant to the analysis of complex materials such as black coal. The use of pulse-to-pulse intensity normalization has the further benefit of extending the period between instrument recalibration, thus enhancing the ease of use of the device. The benefit of the optimized data analysis methodology is revealed in the determination of eight elemental components of gypsum (Na, Ca, Mg, Fe, Al, Si, Ti and K) where a typical absolute analysis accuracy of ±10% is obtained. These results compare favourably to analysis by conventional techniques for these materials. The analysis accuracy and repeatability is further demonstrated by the determination of the concentrations of these elements in a black coal sample.     

电感耦合等离子体发射光谱(ICP-OES)法测定水泥熟料中铬的干扰研究

电感耦合等离子体发射光谱法（ICP-OES）测定重金属时常面临干扰问题。为提高ICP-OES测定水泥熟料中铬的准确度,研究选取了Cr205.560、Cr267.716和Cr283.563三条谱线,根据水泥熟料中主量元素（铁、铝、钙和镁）含量,设计不同浓度单元素干扰试验,结果表明：铁对Cr283.563谱线测定有较大的正干扰,钙对三条谱线均有较大的负干扰,两者导致的相对误差（RE）均在±10%以上,其他一般为负干扰,RE在±10%以内。进一步线性回归分析发现,除铝外,其他干扰元素的干扰大小与浓度呈强线性相关性。通过多元素复合干扰试验发现干扰导致的RE约为-18%~11%,同单元素干扰加和结果比较,两者相差约为8%~10%。实际样品检测结果表明实际干扰同多元素复合干扰试验基本相同,Cr283.563谱线测定结果误差可能更小,三条谱线的实际样品加标回收率大致相当,约为80%,经回收率修正,Cr205.560和Cr267.716谱线结果满意,而Cr283.563谱线误差较大。以多元素复合干扰试验溶液作为基体,采用基体匹配法测定可基本消除干扰影响。以钙溶液作为基体的简化基体匹配法同样有效,但仅可选用Cr205.560和Cr267.716谱线。本研究从实际干扰问题出发,通过系统分析问题,找到干扰的原因,并据此提出消除干扰方法,提高了测定铬的准确度,也为检测人员解决相关干扰问题提供借鉴。     

Absorption of electromagnetic radiation by a nanoparticle in a nanocomposite: Going beyond the Maxwell-Garnett approximation

A model has been proposed for calculating the polarizability of a metal nanoparticle in a composite consisting of a dielectric matrix and monodisperse nanoparticles with more exact allowance for the influence of neighboring particles going beyond the Maxwell-Garnett approximation. The main attention has been focused on the imaginary component of the polarizability, which determines electromagnetic radiation absorption by a nanoparticle in the dipole approximation. It has been shown that the absorption may be noticeably enhanced or diminished depending on the incident radiation frequency.     

Open-path laser-induced plasma spectrometry for remote analytical measurements on solid surfaces

Open-path laser-induced plasma spectrometry has been studied for elemental analysis at a distance of 45 m from the target. The 230-mJ pulsed radiation of a Q-switched Nd:YAG laser at 1064 nm has been used to produce a plasma on the sample and light emission has been collected under an off-axis open-path scheme. Under such conditions, the main variables influencing the signal response such as beam focal conditions, laser incidence angle and laser penetration depth have been identified and diagnosed on the basis of spectral signal-to-noise ratio considerations. The incidence angle is critical beyond 60°. Crater morphology and ablation rates have been studied also. A semi-quantitative analysis of several stainless steel grades has been implemented using a pattern recognition algorithm, which allowed to discriminate successfully the samples on the basis of their variable content in alloying elements.     

Role,effect, and influences of micro and nano‐fillers on various properties of polymer matrix composites for microelectronics: A review

Ever since the discovery of polymer composites, its potential has been anticipated for numerous applications in various fields such as microelectronics, automobiles, and industrial applications. In this paper, we review filler reinforced polymer composites for its enormous potential in microelectronic applications. The interface and compatibility between matrix and filler have a significant role in property alteration of a polymer nanocomposites. Ceramic reinforced polymeric nanocomposites are promising candidate dielectric materials for several micro‐ and nano‐electronic devices. Because of its synergistic effect like high thermal conductivity, low thermal expansion, and dielectric constant of ceramic fillers with the polymer matrix, the resultant nanocomposites have high dielectric breakdown strength. The thermal and dielectric properties are discussed in the view of filler alignment techniques and its effect on the composites. Furthermore, the effect of various surface modified filler materials in polymer matrix, concepts of network forming using filler, and benefits of filler alignment are also discussed in this work. As a whole, this review article addresses the overall view to novice researchers on various properties such as thermal and dielectric properties of polymer matrix composites and direction for future research to be carried out.     

基于黑体辐射提高自由定标激光诱导击穿光谱(CF-LIBS)定量精度的方法

自由定标激光诱导击穿光谱(Calibration-Free LIBS,CF-LIBS)技术是定量分析行业发展的主要趋势之一。该技术可直接基于局部热力学平衡等离子体模型,通过LIBS光谱数据和谱线参数计算出等离子体参数和各元素含量。且无需使用标准样品建立定标曲线,该技术不受基体效应的影响,非常适合实时、在线和多元素同时分析。但由光学厚而引起的自吸收效应是影响定量分析的重要因素。通过对比实验光谱数据与黑体辐射强度,研究等离子体温度,提高光学系统收集效率,抑制自吸收效应对CF-LIBS定量结果的影响。经过黑体辐射校正后,基体元素Fe的测定含量从88.700%提升到94.575%,相对误差(RE)从8.072%降低到1.984%。微量元素Cr、Mo和V的测定含量分别从0.635%、0.096%和0.023%降低至0.698%、0.143%和0.022%,相对误差(RE)从13.723%、45.455%和21.053%降低至5.163%、18.75%和15.789%。整体的平均绝对误差(MAE)从1.994%降低至0.497%。玻尔兹曼图拟合回归曲线有了更高的线性度。拟合系数R²     

Theory of space-charge polarization for determining ionic constants of electrolytic solutions

A theoretical expression of the complex dielectric constant attributed to space-charge polarization has been derived under an electric field calculated using Poisson's equation considering the effects of bound charges on ions. The frequency dependence of the complex dielectric constant of chlorobenzene solutions doped with tetrabutylammonium tetraphenylborate (TBATPB) has been analyzed using the theoretical expression, and the impact of the bound charges on the complex dielectric constant has been clarified quantitatively in comparison with a theory that does not consider the effect of the bound charges. The Stokes radius of TBA+(=TPB-) determined by the present theory shows a good agreement with that determined by conductometry in the past; hence, the present theory should be applicable to the direct determination of the mobility of ion species in an electrolytic solution without the need to measure ionic limiting equivalent conductance and transport number.     

Modeling interband transitions in silver nanoparticle-fluoropolymer composites

The interband transition contributions to the optical properties of silver nanoparticles in fluoropolymer matrices are investigated. For the materials in this study, nanoparticle synthesis within the existing polymer matrix is accomplished using an infusion process that consists of diffusing an organometallic precursor gas into the free volume of the fluoropolymer and decomposing the precursor followed by metal nanoparticle nucleation and growth. The resulting polymer matrix nanocomposite has optical properties that are dominated by the response of the nanoparticles owing to the broadbanded transparency of the fluoropolymer matrix. The optical properties of these composites are compared to Maxwell-Garnett and Mie theory with results indicating that interband transitions excited in the silver nanoparticles affect the optical absorption over a range of frequencies including the surface plasmon resonance. It is shown that calculations of the optical absorption spectrum using published data for the silver dielectric function do not accurately describe the measured material response and that a classical model for bound and free electron behavior can best be used to represent the dielectric function of silver.     

Multi-elemental analysis of solidified mineral melt samples by Laser-Induced Breakdown Spectroscopy coupled with a linear multivariate calibration

Laser-Induced Breakdown Spectroscopy (LIBS) has been successfully applied for multi-elemental analysis of solidified mineral melt samples containing several oxides present in various concentrations. The plasma was generated using a Nd:YAG laser and the spectra were acquired using an Echelle spectrometer, coupled to an ICCD detector, which covers a spectral range from 200 to 780 nm. Using a set of 19 calibration samples, we first established univariate calibration curves for the major elements (Al, Fe, Mg, Ca, Ti and Si). We found out that the presence of matrix effects makes such a model, traditionally used in LIBS, not satisfying for quantitative analysis of such samples. Indeed, no sufficiently linear trends can be extracted from the calibration curves for the elements of interest considering all the samples. Instead, a much more robust calibration approach was obtained by considering a multivariate model. The matrix effects are then taken into account by correcting the spectroscopic signals emitted by a given species due the presence of the others ones. More specifically, we established here a calibration model using a 2nd order polynomial linear multivariate inverse regression. The capability of this approach was then checked using a 2nd set of samples with an unknown composition. A good agreement was observed between the analysis provided by X-ray fluorescence (XRF) and the LIBS measurements coupled to the multivariate model for the unknown samples.     

Charge trapping and dielectric relaxations of gamma irradiated radiolytically oxidized highly oriented LDPE

The influence of gamma irradiation in air on the effects of charge trapping in highly oriented LDPE has been studied through dielectric loss (tan δ) analysis in the temperature range from 25 to 325 K and using thermally stimulated discharge current (TSDC) measurements. The radiation induced oxidation was observed using IR spectroscopy. The intensity and the position of the γ and β dielectric relaxation maxima were correlated with maxima of TSDC measurements. It was found that the positions of the relaxation peaks are strongly dependent upon the changes in the microstructure of the amorphous phase and on the surface of the crystallites induced by orientation and gamma irradiation.     

Study of Matrix Effects on Determination of Trace Elements in Aluminum,Using Inductively Coupled Plasma Atomic Emission Spectrometry, 1) Selection of Spectral Lines.

Abstract

The effect of an aluminum matrix on the determination of B, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Si and Zn was studied. These elements are expected to be present in high purity Al base materials. 45 spectral lines of these elements were scanned in a spectral window of 60 pm. Background equivalent concentrations were calculated and compared with existing data. Interference free spectral lines, one for each element, have been recommended to be used for analysis. Depression effects due to the Al matrix were calculated at the selected lines.     

Variable alignment of high resolution data by cluster analysis

High resolution time-of-flight secondary ion mass spectrometry (HR TOF-SIMS) is a powerful surface analytical method. For complex samples, this technique may yield intricate spectra that are difficult to interpret visually. Chemometric methods are useful for data analysis. However, these methods require that spectra are represented in a matrix format. Variances in mass measurements caused by calibration or instrumental effects may present difficulties in properly aligning mass spectral peaks into the correct columns of the data matrix. Cluster analysis of resolution elements is proposed as an alternative approach to construct the data matrix. An automated method for optimizing the data alignment is presented and evaluated for standard steel samples.     

A portable absorption-fluorometer for detection of organic substances in fluids

Using the method of multipath-saturation fluorescence, which considers both fluorescent as well as nonfluorescent substances, the total absorption coefficient can be determined with high sensitivity. This new fluorescence method is appropriate, e.g. for in-situ applications. Thus a portable absorption-fluorometer has been constructed. The main part of the device is a multireflection cell based on a design of Herriott with a 1 cm quartz-cuvette. Two pairs of spherical dielectric mirrors are used to realize the multireflection of the excitation radiation in the UV and blue spectral range. The combination of a cylindrical and a convace mirror leads to a long pathway of the excitation radiation and, thus, to a full absorption by the fluid. A first experiment has been performed with drinking water samples defined polluted by non-fluorescent p-nitrophenol and 2-nitroaniline. Based on the method of multipath-saturation fluorescence a good correlation to the substance concentration was achieved, whereas the conventional absorption failed.     

A portable absorption-fluorometer for detection of organic substances in fluids

Using the method of multipath-saturation fluorescence, which considers both fluorescent as well as nonfluorescent substances, the total absorption coefficient can be determined with high sensitivity. This new fluorescence method is appropriate, e.g. for in-situ applications. Thus a portable absorption-fluorometer has been constructed. The main part of the device is a multireflection cell based on a design of Herriott with a 1 cm quartz-cuvette. Two pairs of spherical dielectric mirrors are used to realize the multireflection of the excitation radiation in the UV and blue spectral range. The combination of a cylindrical and a convace mirror leads to a long pathway of the excitation radiation and, thus, to a full absorption by the fluid. A first experiment has been performed with drinking water samples defined polluted by non-fluorescent p-nitrophenol and 2-nitroaniline. Based on the method of multipath-saturation fluorescence a good correlation to the substance concentration was achieved, whereas the conventional absorption failed.     

Modification of submicron barium titanate particles via sol-gel synthesis of interface layers of SiO2 for fabrication of polymer-inorganic composites with improved dielectric properties

Modification of the surface of submicron BaTiO₃ particles by SiO₂ layer using sol-gel method has led to significant (>50%) increase in the dielectric permittivity and decrease in the dielectric losses of the composites prepared via introduction of BaTiO₃ into a matrix of poly(vinyl alcohol) cyanoethyl ester. The effect has been due to the formation of basic hydroxy groups (Brønsted centers) at the filler surface; these groups can interact with weakly acidic hydroxyl groups of poly(vinyl alcohol) cyanoethyl ester, thus improving the compatibility of the polymer matrix and the filler.     

Surface characterization by spectroscopic infrared ellipsometry

Summary For ellipsometry in the infrared range the advantages of Fourier-transform spectroscopy can be exploited when the experimental procedure is based on photometry. The measured intensities are interpretable in terms of the so-called ellipsometric parameters which describe the polarization state of the radiation after having been reflected from the sample. These parameters in turn are correlated with the optical constants of the sample such as the dielectric function or the complex refractive index as well as with its geometrical structure. The potential of spectroscopic infrared ellipsometry for the characterization of surfaces and surface films is demonstrated by examples including compounds with spectral intervals of strong absorption and assemblies of semiconductor films.     

Chemical fractionation of a fly ash sample by a sequential leaching method

A five-stage sequential leaching procedure was optimized for the analysis of the fly ash sample, CW6, as a candidate reference material. The distribution of particulate elements was achieved for Cd, Cr, Cu, Pb, Zn, and V into different fractions: (1) exchangeable, (2) bound to carbonate, (3) bound to Fe/Mn oxides, (4) bound to sulfide compounds, and (5) acid soluble, residual fraction. The leachability of the metals proved to be different, so various distribution patterns have been achieved. The results of the total elemental analysis and the sequential leaching method were compared and a good agreement was found. The uncertainty of the leaching method is reasonable, even when experimental parameters are strictly fixed and the analysis is quite tedious. The ratio of environmentally mobile fractions was compared to that from the conventional test method and a reasonable conformity has been found. This characterization method can be used to interpret the leaching behavior of element species and mode of binding to the matrix. Using the optimized sequential procedure, a new aspect can be interpreted to understand the behavior of toxic elements released from fly ashes into nature.