Results of a joint auger/ESCA round robin sponsored by astm commitree E-42 on surface analysis: Part I. Esca results

We report results of a round robin involving binding-energy (BE) and relative-intensity measurements on high-purity samples of gold and copper by X-rayWe have conducted an extensive round robin involving ESCA or XPS measurements on high-purity samples of Ni, Au, and Cu. The Ni sample was used to estabThis round robin had three principal objectives. First, it was intended to assess the overall accuracy of BE and intensity measurements in XPS measuremSecond, it was intended to establish an empirical intensity calibration of one type of XPS instrument versus another from the reported intensity ratiosThird, it was desired to determine the peak position and peak shape for the carbon 1s photoelectron line originating for “adventitious” carbonaWe have made an extensive analysis of trends in the BE and intensity data. We have computed deviations of individual BE measurements from the median vaThe two types of plots just described based on BE and intensity data can be regarded as “response functions” that describe the performance of indivWe have invoked Occam's Razor to distinguish instruments with response functions which vary monotonically with electron energy from those instruments wThe reported spreads in BE and relative-intensity data reported here indicate that improved calibration and operating procedures are required for XPS m     

Results of a joint auger/esca round robin sponsored by astm committee E-42 on surface analysis. Part II. Auger results

We report the results of a round robin involving kinetic-energy (KE) and relative-intensity measurements on high-purity samples of copper and gold by Auger-electron spectroscopy. These results were obtained using 28 different instruments or analyzers manufactured by four companies. We found that the spread in reported KE values ranged from 7 eV at a KE of 60 eV to 32 eV at a KE of ～2025 eV. The total spread in reported intensity ratios ranged from a factor of ～38 for the ～6O eV and ～92O eV peaks of Cu to a factor of $\text{~}\text{?}$120 for the ～70 eV and ～2025 eV peaks of Au. We have analyzed the observed trends in some detail. The systematic error of kinetic-energy measurements increases with kinetic energy for many instruments. Even though all instruments were adjusted with the use of 2 keV elastically scattered electrons, the spread in the reported positions of the ～2025 eV Au peak indicates that the instruments were not adequately calibrated. Examples of erratic response were found in the measurements of relative intensities; it was believed, though not proved, that the more extreme values of intensity ratios were associated with instrumental malfunctions or operator mistakes. As in the similar ESCA round robin (Part I), the spread in reported Auger kinetic energies and relative intensities demonstrates clearly the need for standards (e.g., calibration methods, operating procedures, and data analysis) to ensure that data of known accuracy can be obtained routinely. Until suitable standards are available, interested individuals may find it useful to compare measurements using their own Auger or ESCA instruments with the group results and the trends found in the round-robin results.We have conducted an extensive round robin consisting of AES measurements on high-purity samples of Cu and Au. Participants were asked to measure the kinetic energies and relative intensifies of designated Auger peaks under specified conditions. This round robin was conducted contemporaneously with a similar ESCA round robin, the results of which have already been published [1].The AES round robin had three principal objectives. First, it was intended to assess the overall accuracy of KE and relative-intensity measurements in a relatively straightforward AES measurement. An earlier round robin [2] with catalyst samples demonstrated substantial spreads of reported data, and it was believed that comparisons of data obtained for cleaned metallic samples should give a more accurate picture of the current state-of-the-art. With a larger number of participants in the present round robin than in the catalyst round robin, we in fact find a comparable spread in the raw data. The spread in the reported KE measurements is a function of kinetic energy, and ranges from 7 eV at a KE of 60 eV to 32 eV at a KE of 2 keV. The imprecision of the KE measurements is typically ～1–3 eV. The total spread in the reported intensity ratios ranges from a factor of ～38 for Cu (at an incident energy of 3 keV) to a factor of ～120 for Au (at the same incident energy). The imprecision of the intensity ratios is typically less than 10%.Second, it was desired to determine the variation of AES intensities as a Cu sample was displaced along the analyzer axis with respect to its optimum position. Many of the participants found maxima in the intensities of the Cu ～60 eV and ～920 eV peaks at or very close to that sample position found to be optimum for the 2 keV elastic peak. Other participants found intensity maxima at sample positions up to ～4 mm away from the 2 keV elastic-peak position; these participants found that when the sample was at the optimum position for the 2 keV elastic peak, the intensities of the ～60 eV and ～920 eV Cu peaks could be as low as 50% of the corresponding maximum peak intensities that were found when the sample was displaced.Third, it was intended to measure the Auger KE for the “adventitious” carbon that forms on initially clean samples in the ambient vacuum of each instrument. Few participants made this measurement, although it was observed that the spread of reported energies for the carbon Auger peak was comparable to that found for the low-energy (60–7OeV) peaks in Cu and Au.We have examined the KE and relative-intensity data in some detail. We found it useful to compute deviations of individual KE measurements from the median values of the reported measurements for the selected Auger peaks. These deviations were plotted as a function of kinetic energy and lines were drawn connecting data points obtained using the same instrument. Such plots can be regarded as “error functions” or “calibration curves” based on the use of the group median values as reference data. These curves indicate that for many instruments the error of KE measurements increases approximately linearly with KE (unlike the behavior found in similar plots for binding-energy measurements in the ESCA round robin, in which the error was often nearly constant or slowly varying with binding energy). The large spread (32 eV) in the reported positions of the Au M₅N_6,7N_6,7 peak at a KE of ～2024 eV was considered particularly significant, since most instruments were adjusted and aligned using elastically scattered electrons at an energy of 2 keV. This observation clearly indicates that the working KE scales of the instruments were not adequately calibrated using the elastic-peak method; this problem is believed to be due to the insufficient accuracy of the 2 kV power supplies or the voltmeters used to display the KE scales rather than to any intrinsic deficiencies in the use of the elastic-peak method. There were several examples, however, in which plots of the intensities of the ～60 eV and ～920 eV Cu peaks as a function of sample position had maxima for both peaks at a position different from that found optimum for the 2 keV elastic peak. These observations indicate that sample alignment by the elastic-peak method was not done with sufficient accuracy in some laboratories. Finally, while the imprecision in the locations of the elastic peak and of Auger peaks in the round robin was typically 1–3 eV, the overall inaccuracy of the KE measurement was usually substantially larger.Most participants found that ratios of peak heights for the low-energy and high-energy transitions in Cu and Au decreased slowly as the incident electron energy was increased from 3 keV to 8 keV. Some participants, however, obtained qualitatively different dependences on incident energy; these results were attributed to mistakes, instrument malfunctions, or to inadequate alignment. Our experience in the ESCA round robin indicated that operator mistakes or instrumental problems were responsible for most of the outliers in comparisons of measured intensity ratios. We suspect (although we have not proved) that the more extreme values of peak-height ratios in the AES round robin have a similar origin. The AES intensity data were analyzed to search for mechanisms that could account for the large range of reported intensity ratios. We considered several possible origins for the more extreme data values. First, we examined the reported peak-height ratios for Cu and Au, to search for possible variations of the instrumental transmission functions from their “ideal” values. Second, we considered whether relatively large amounts of residual surface carbon could account for the observed intensity ratios. Third, we tested whether the instruments which exhibited “non-ideal” behavior (probably because of significant stray magnetic fields or inadequate sample alignment) when the samples were translated parallel to the analyzer axis were also the ones which gave the more extreme peak-height ratios. Fourth, we investigated whether probable variations in the amplitude of the modulation voltage applied to the analyzers would modify significantly the ratios of the observed intensities. Fifth, we considered the effects of the differing energy resolutions of the analyzers in the round robin. Finally, we considered effects due to variations in surface roughness caused by the different ion-sputtering conditions used for initial cleaning of the samples. None of these factors alone could account for the more extreme variations of the peak-height ratios, although it is possible that some of these factors could affect certain specific instruments while a different combination of the factors could be important in other cases. Although we were unable to demonstrate conclusively the nature of instrumental artifacts or possible operator mistakes in the various intensity measurements, we believe that the spread in the reported intensity ratios is associated with specific measurement problems in particular individual laboratories. A variety of factors have been identified here to account for the more modest but nevertheless distressing range of intensity ratios (a factor of ～2 for Cu and of ～5 for Au) for the majority of the participants.The spreads in the energies and relative intensities of Auger and photoelectron peaks in this AES and the previous ESCA round robin indicate clearly that improved calibration and operating procedures are required for both Auger and ESCA measurements. Published data, for example, are of little value unless credible statements of accuracy can be associated with the numerical results. We hope that the standards needed for improved measurements can be developed by the ASTM Committee E-42 on Surface Analysis together with other interested parties.     

An evaluation of three adaptive hearing aid selection strategies

Paired-comparison judgments of intelligibility of speech in noise were obtained from eight hearing-impaired subjects on a large number of hearing aids simulated by a digital master hearing aid. The hearing aids which comprised a 5 X 5 matrix differed systematically in the amount of low-frequency and high-frequency gain provided. A comparison of three adaptive strategies for determining optimum hearing aid frequency-gain characteristics (an iterative round robin, a double elimination tournament, and a modified simplex procedure) revealed convergence on the same or similar hearing aids for most subjects. Analysis revealed that subjects for whom all three procedures converged on the same hearing aid showed a single pronounced peak in the response surface, while a broader peak was evident for the subjects for whom the three procedures identified similar hearing aids. The modified simplex procedure was found to be most efficient and the iterative round robin least efficient.     

Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni

Chemical state X-ray photoelectron spectroscopic analysis of first row transition metals and their oxides and hydroxides is challenging due to the complexity of their 2p spectra resulting from peak asymmetries, complex multiplet splitting, shake-up and plasmon loss structure, and uncertain, overlapping binding energies. Our previous paper [M.C. Biesinger et al., Appl. Surf. Sci. 257 (2010) 887-898.] in which we examined Sc, Ti, V, Cu and Zn species, has shown that all the values of the spectral fitting parameters for each specific species, i.e. binding energy (eV), full wide at half maximum (FWHM) value (eV) for each pass energy, spin-orbit splitting values and asymmetric peak shape fitting parameters, are not all normally provided in the literature and data bases, and are necessary for reproducible, quantitative chemical state analysis. A more consistent, practical and effective approach to curve fitting was developed based on a combination of (1) standard spectra from quality reference samples, (2) a survey of appropriate literature databases and/or a compilation of literature references and (3) specific literature references where fitting procedures are available. This paper extends this approach to the chemical states of Cr, Mn, Fe, Co and Ni metals, and various oxides and hydroxides where intense, complex multiplet splitting in many of the chemical states of these elements poses unique difficulties for chemical state analysis. The curve fitting procedures proposed use the same criteria as proposed previously but with the additional complexity of fitting of multiplet split spectra which has been done based on spectra of numerous reference materials and theoretical XPS modeling of these transition metal species. Binding energies, FWHM values, asymmetric peak shape fitting parameters, multiplet peak separation and peak area percentages are presented. The procedures developed can be utilized to remove uncertainties in the analysis of surface states in nano-particles, corrosion, catalysis and surface-engineered materials.     

现代仪器在泌尿系结石元素分析中的运用

对泌尿系结石所含元素进行准确的分析可为治疗尿石症和预防其复发提供重要的参考,文章综述了现代仪器分析技术在泌尿系结石元素分析中的运用及其研究进展,这些技术包括：X射线光电子能谱(XPS)、质子激发X射线发射光谱(PIXE)、能量分散X射线分析(EDX)、电子束探针微区分析(EPMA)、原子发射光谱(AES)、原子吸收光谱(AAS)、电感耦合高频等离子体发射光谱(ICP)、X射线荧光光谱(XRF)及离子选择性电极等。     

A reproducible test to characterise the triboelectric charging of powders during their pneumatic transport

Although several investigations had been carried out to explore the triboelectrification of powders, only few data are available on the experimental procedures and set-ups required to obtain reliable data. The present study deals with the development of a pneumatic test to characterise the tribocharging of fine powders. An experimental device was set up allowing on-line monitoring of the charge of both particles and transport pipes. Experiments were carried out using two types of powder (fine sugar and PVC) coupled with two types of pipe materials (Teflon and nylon). Results showed the extreme importance of the control of the relative humidity, the initial charge of particles and the charge dissipation of the walls to obtain pertinent data. Furthermore, the results showed that solids loadings higher than 1 (kg of solids/kg of air) are not proper to achieve reliable measurements. However, at very dilute solids loading (～0.001) the time evolutions of the electrostatic charge and the mass of the powder follow similar trends so that the tribocharging becomes independent of the solids mass flowrate. This allows accurate assessment of the tribocharging of cohesive powders for which a regular flow cannot be guaranteed.     

X射线光电子能谱

X射线光电子能谱（X-ray photoelectron spectroscopy，XPS）技术也被称作用于化学分析的电子能谱（electron spectroscopy for chemical analysis，ESCA）．XPS属表面分析法，它可以给出固体样品表面所含的元素种类、化学组成以及有关的电子结构重要信息，在各种固体材料的基础研究和实际应用中起着重要的作用．文章简要介绍了XPS仪器的工作原理和分析方法，并给出了XPS在科学研究工作中的应用实例．     

LABORATORY TESTING OF RADIANT GAS BURNERS AND ELECTRIC INFRARED EMITTERS

A project focusing on industrial infrared technology was carried out at Hydro-Québec's LTEE laboratory [1], The project required the optimization and use of a special test facility. Seven electric emitters and seven radiant gas burners typically used in the textile and pulp and paper industries were evaluated. Three types of experiments were carried out, providing four types of information: radiant flux maps, radiant efficiency evaluation, transient behavior characterization, and spectral emission characterization. The apparatus and the experimental procedures are described. Results are discussed and are presented in the form of tables and graphs. As the procedure and instruments used within each test were identical, this work furnishes rigorous data and objective information on both electric and gas IR technologies.     

Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Sc, Ti, V, Cu and Zn

Chemical state X-ray photoelectron spectroscopic analysis of first row transition metals and their oxides and hydroxides is challenging due to the complexity of the 2p spectra resulting from peak asymmetries, complex multiplet splitting, shake-up and plasmon loss structure, and uncertain, overlapping binding energies. A review of current literature shows that all values necessary for reproducible, quantitative chemical state analysis are usually not provided. This paper reports a more consistent, practical and effective approach to curve-fitting the various chemical states in a variety of Sc, Ti, V, Cu and Zn metals, oxides and hydroxides. The curve-fitting procedures proposed are based on a combination of (1) standard spectra from quality reference samples, (2) a survey of appropriate literature databases and/or a compilation of the literature references, and (3) specific literature references where fitting procedures are available. Binding energies, full-width at half maximum (FWHM) values, spin-orbit splitting values, asymmetric peak-shape fitting parameters, and, for Cu and Zn, Auger parameters values are presented. The quantification procedure for Cu species details the use of the shake-up satellites for Cu(II)-containing compounds and the exact binding energies of the Cu(0) and Cu(I) peaks. The use of the modified Auger parameter for Cu and Zn species allows for corroborating evidence when there is uncertainty in the binding energy assignment. These procedures can remove uncertainties in analysis of surface states in nano-particles, corrosion, catalysis and surface-engineered materials.     

A traceable quantification procedure for a multi-mode X-ray photoelectron spectrometer

A modification to the quantification procedure used by a multi-mode X-ray photoelectron spectrometer (XPS) instrument is described which enables transfer of quantification between instruments, and which is referenced to a verified source. The procedure takes account of the intensity/energy response function of the instrument, which is appended to the data file, eliminating ambiguities in intensity calibration at a later date, and allowing background subtraction techniques based on electron scattering to be used on corrected spectra. A strategy is proposed to minimise inaccuracies arising from surface contamination and low signal intensity. Use of the procedure is illustrated by comparing quantification using different data processing software.     

Surface chemistry of Nextel-720, alumina and Nextel-720/alumina ceramic matrix composite (CMC) using XPS–A tool for nano-spectroscopy

Oxide-based ceramic matrix composites (CMCs) are prime candidates for high temperature turbine applications. Increasing demand of CMCs necessitates the development of quality monitoring procedures. Sol–gel derived Nextel-720 fiber/alumina matrix CMC is one of the potential candidate material for land-based gas turbine applications. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) were utilized to investigate any surface/interface chemical alteration of the Nextel-720 fiber reinforcement and the alumina matrix during fabrication. The calculated XPS spectra of the composite were obtained by simply adding the spectra of the as-received Nextel-720 fiber and the alumina matrix. The calculated XPS spectra and the acquired XPS Al(2p), Si(2p³), and O(1s) spectra from the as-received materials were compared using a superimposition method to investigate any chemical alteration during composite fabrication for quality control measures. This paper is aimed to serve as a reference for future XPS studies of CMCs exposed to aggressive turbine environments.     

Detergency of stainless steel surface soiled with human brain homogenate: an XPS study

In the detergency field of re-usable medical devices, a special attention is focused on the non conventional transmissible agent called prions which is a proteinaceous infectious agent. Few cleaning procedures are effective against prions and few techniques are available to study cleaning effectiveness with respect to proteins in general. In our study, X-ray photoelectron spectroscopy (XPS) has been used to evaluate the effectiveness of detergent formulations to remove proteins from stainless steel surface soiled with a brain homogenate (BH) from human origin. Our results showed that XPS is a reliable surface analysis technique to study chemical species remaining on surface and substrate properties after cleaning procedures. A semi-quantitative evaluation of the detergency effectiveness could also be performed.     

Characterization challenges for a cellulose nanocrystal reference material: dispersion and particle size distributions

Cellulose nanocrystals (CNCs) have high aspect ratios, polydisperse size distributions, and a strong propensity for aggregation, all of which make them a challenging material for detailed size and morphology characterization. A CNC reference material produced by sulfuric acid hydrolysis of softwood pulp was characterized using a combination of dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy, and X-ray diffraction. As a starting point, a dispersion protocol using ultrasonication was developed to provide CNC suspensions with reproducible size distributions as assessed by DLS. Tests of various methods for AFM sample preparation demonstrated that spin coating on a positively charged substrate maximizes the number of individual particles for size analysis, while minimizing the presence of agglomerates. The effects of sample-to-sample variability, analyst bias, and sonication on size distributions were assessed by AFM. The latter experiment indicated that dispersion of agglomerates by sonication did not significantly change the size distribution of individual CNCs in suspension. Comparison with TEM data demonstrated that the two microscopy methods provide similar results for CNC length (mean ~?80 nm); however, the particle width as measured by TEM is approximately twice that of the CNC height (mean 3.5 nm) measured by AFM. The individual crystallite size measured by X-ray diffraction is intermediate between the two values, although closer to the AFM height, possibly indicating that laterally agglomerated CNCs contribute to the TEM width. Overall, this study provides detailed information that can be used to assess the factors that must be considered in measuring CNC size distributions, information that will be useful for benchmarking the performance of different industrially sourced materials.     

An international round-robin calibration protocol for nanoindentation measurements

Nanoindentation has become a common technique for measuring the hardness and elastic-plastic properties of materials, including coatings and thin films. In recent years, different nanoindenter instruments have been commercialised and used for this purpose. Each instrument is equipped with its own analysis software for the derivation of the hardness and reduced Young's modulus from the raw data. These data are mostly analysed through the Oliver and Pharr method. In all cases, the calibration of compliance and area function is mandatory. The present work illustrates and describes a calibration procedure and an approach to raw data analysis carried out for six different nanoindentation instruments through several round-robin experiments. Three different indenters were used, Berkovich, cube corner, spherical, and three standardised reference samples were chosen, hard fused quartz, soft polycarbonate, and sapphire. It was clearly shown that the use of these common procedures consistently limited the hardness and reduced the Young's modulus data spread compared to the same measurements performed using instrument-specific procedures. The following recommendations for nanoindentation calibration must be followed: (a) use only sharp indenters, (b) set an upper cut-off value for the penetration depth below which measurements must be considered unreliable, (c) perform nanoindentation measurements with limited thermal drift, (d) ensure that the load-displacement curves are as smooth as possible, (e) perform stiffness measurements specific to each instrument/indenter couple, (f) use Fq and Sa as calibration reference samples for stiffness and area function determination, (g) use a function, rather than a single value, for the stiffness and (h) adopt a unique protocol and software for raw data analysis in order to limit the data spread related to the instruments (i.e. the level of drift or noise, defects of a given probe) and to make the H and E(r) data intercomparable.     

Surface composition of Fe-Al2O3 granular thin films by X-ray photoemission spectroscopy

X-ray photoemission Spectroscopy (XPS) results are presented which have given a direct insight into the surface composition of Fe-Al₂ O₃ “granular” thin films consisting of fine iron particles (φ ~ 40–150 Å) dispersed in an insulating alumina matrix. The data are mainly discussed in relation to: (i) the bulk iron content in the sample, (ii) the sample preparation procedure (e.g., by rotation of the sample target) and (iii) the mean iron particle size.At the surface, the iron is in a fully oxidized 3⁺ state within an alumina-rich partly hydrated region. Depth analysis, achieved by an Ar⁺ etching procedure, provides evidence of metallic iron and iron aluminate forms. In general, the metallic iron percentage increases with depth and with increasing iron bulk content.Good agreement is found between X-ray photoemission spectroscopy and Mössbauer Spectroscopy data. Fe²⁺ aluminate forms, which indicate an interaction between the metal particle and the alumina matrix, show increasing percentages with decreasing mean particle sizes.Particular attention is paid to evaluating the accuracy of XPS quantitative results, obtained by use of a first-principles model, and to assessing the importance of the artefacts associated with the Ar⁺ etching procedure.     

3D reconstruction of objects using stereo imaging

This paper describes two stereo imaging experimental set-ups useful in measuring the 3D geometry of objects: a parallel optical-axis model and a converging optical-axis model. Digital image correlation is used to find the disparities between corresponding points in a pair of images, for each of these models, with subpixel accuracy. To show the application of the developed algorithms and the stereo imaging experimental set-ups, four different body geometries are used. For some of the objects tested a higher measuring accuracy is obtainable from the converging optical-axis experimental set-up.     

A user-friendly nano-CT image alignment and 3D reconstruction platform based on Lab VIEW

X-ray computed tomography at the nanometer scale(nano-CT) offers a wide range of applications in scientific and industrial areas. Here we describe a reliable,user-friendly,and fast software package based on Lab VIEW that may allow us to perform all procedures after the acquisition of raw projection images in order to obtain the inner structure of the investigated sample. A suitable image alignment process to address misalignment problems among image series due to mechanical manufacturing errors,thermal expansion,and other external factors has been considered,together with a novel fast parallel beam 3D reconstruction procedure that was developed ad hoc to perform the tomographic reconstruction. We have obtained remarkably improved reconstruction results at the Beijing Synchrotron Radiation Facility after the image calibration,the fundamental role of this image alignment procedure was confirmed,which minimizes the unwanted blurs and additional streaking artifacts that are always present in reconstructed slices. Moreover,this nano-CT image alignment and its associated 3D reconstruction procedure are fully based on Lab VIEW routines,significantly reducing the data post-processing cycle,thus making the activity of the users faster and easier during experimental runs.     

仪器分析技术在未知物鉴定上的应用

本文运用红外光谱、能谱、X衍射等多种仪器对一未知样品进行了联合定性与定量分析,采用各种仪器的特点,逐步剖析了未知样品,并且确定了样品的化学组成,此项工作对于无机物的分析具有一定的指导作用。     

X-ray diagnostics of semiconductor heterostructures: Some achievements and perspectives for development

Possibilities of new approaches for the interpretation of X-ray scattering data to characterize heterostructures with nanosized layers are demonstrated. These approaches are based on both simultaneous mathematical analysis of the experimental data of X-ray rocking curves from several crystallographic planes of the sample and joint processing of the experimental data of X-ray diffraction and reflectometry. Measurements are taken using the same device with the advanced technique of experiments. In the approaches proposed, the volume of the experimental information on one sought parameter increases significantly, which provides a greater reliability of reconstructing the structural parameters of the object under study. A mathematical apparatus is developed along with the software to solve the inverse problem with a large amount of input data and sought parameters. The proposed approaches are tested on nanosized Al_xGa_1-xAs/In_yGa_1-yAs and In_xAl_1-xAs/In_yGa_1-yAs heterostructures grown on GaAs and InP substrates, respectively. It is shown that the complex X-ray method allows a reliable determination of relationships between the real structure and electrophysical properties, and thus an improvement of the technology for producing these objects with predicted properties.