bluuebunny/crossref_metadata_2025 huggingface dataset:
Particle‐Induced Limits of Accuracy in Laser Doppler Anemometry
Authors: Ruck Bodo , Pavlovski Boris
Published: December 2004

Laser Doppler anemometry (LDA) is one of the most advanced optical measuring techniques for flow velocities and is widely used in industrial and academic laboratories. Based on numerous applications in the past, there is no doubt that LDA is one of the most accurate flow measuring techniques. However, recent investigations have shown that the period lengths of LDA signal bursts are not as constant as one might expect within the individual burst. This can induce an additional scatter in the signal frequency and in the determination of flow velocity from individual bursts. This paper describes experimental investigations which show qualitatively and quantitatively that the particle passage through the laser beams shortly before the point of intersection, i. e. the LDA measuring volume, yields a distorted LDA fringe pattern. The latter results in a scatter of the measured velocity data for those particles passing the center of the measuring volume at the same time.
Generalized Theory for the Simultaneous Measurement of Particle Size and Velocity using laser doppler and laser two‐focus methods
Authors: Albrecht Heinz‐E. , Borys Michael , Hübner Klaus
Published: December 2004

Essentially the laser two‐focus (L2F) and laser Doppler anemometer (LDA) are time‐of‐flight anemometers. The velocity of particles in the micrometre range is determined within the limits of an optically fixed measurement distance. For this only one optoelectronic receiver for the detection of the scattered light is required [1, 2]. With an arrangement of two receiving optics, positioned under an off‐axis angle φ and an elevation angle ± ψ to the optical axis of the measurement system, a resolution of three‐dimensional structures can be achieved and with regard to spherical particles it is possible to determine the dimensions by means of the temporal or phase shift of the signals in the receiving optics. A particle size‐dependent distance inside the measurement volume can be fixed, which has to be passed in order to change the signal from one receiving optics to the other. An LDA with an arrangement of two receiving optics for particle sizing is known as a phase Doppler anemometer (PDA); an L2F designed with two receiving optics can be termed a pulse‐displacement two‐focus anemometer (P2F). The physical analysis of the two methods with respect to a temporal signal displacement in the receivers yielded new results.
Particle Mass Loading Effect on a Two‐Phase Turbulent Downward Jet Flow
Authors: Jou Biing‐Hwang , Sheen Horn‐Jiunn , Lee Yuh‐Tzyh
Published: December 2004

The particle mass loading effect on the flow structure of a two‐phase turbulent jet flow was studied. A particle mass loading ratio ranging from 0 to 3.6 was used as the control parameter. The polystyrene solid particles used had nominal diameters of 210 and 780 μm. The flow Reynolds number, which was based on the pipe nozzle diameter and the fluid‐phase centerline mean velocity, was 2 × 104 in the current test. A two‐color laser Doppler anemometer (LDA), combined with the amplitude discrimination method and the velocity filter method, was employed to measure the mean velocity distributions for the particle and fluid phases, and the turbulent intensities and Reynolds stresses of the flow. The two‐phase jet flow field was measured from the initial pipe exit to 90 D downstream. Another one‐component HeNe laser LDA system was also applied to obtain the energy spectra and temporal correlations of the two‐phase jet flow.
Light Scattering by Anthophyllite‐Crocidolite Asbestos Fibers. Part II: Comparison of various approximate theories with the EBCM theory
Authors: Lapalme René , Patitsas Tom A. J.
Published: December 2004

The effect of the geometry of the fiber ends on the scattered intensities is considered. A new modification of the Rayleighdebye‐Gans (RDG) approximate theory, the Mie Substitution Theory (MST) theory, is introduced. The Boundary Value Method (BVM) for the infinite cylinder, the RDG theory, the Shifrin (SFR) modification of the RDG theory and the MST theory are compared with the EBCM theory for various values of fiber diameter, length, refractive index and for various fiber orientations, including random orientation. Scattering from suspensions of fibers, typical of UICC crocidolite and anthophyllite asbestos fibers, is considered using the BVM, the MST and the RDG theories when the fibers are assumed to be aligned and the MST and the RDG theories when the fibers are assumed to be randomly oriented.
Comparison of Dry Test Sieving on Woven Wire Cloths versus electroformed sheets
Authors: Besancon Pierre , Chastang Jean , Lafaye Albert
Published: December 2004

Dry test sieving results given by woven wire cloths with a square mesh and by round electroformed apertures were compared using sands of various origin. The difference has been found to be constant and independent of substance and quantile. The quantile obtained on a square mesh was converted into the corresponding quantile on an electroformed sheet of the same nominal aperture by multiplication by a constant factor of 1.21 ± 0.04.
The Use of Laser Backscatter Instrumentation for the on‐line measurement of the particle size distribution of emulsions
Authors: Sparks Ronald G. , Dobbs Charles L.
Published: December 2004

The response of the Partec laser backscatter particle size analyzer has been tested under a variety of conditions. Various materials posessing different light scattering characteristics have been examined and the response of the Partec instrument has been evaluated. In particular the system response to transparent particle systems (e.g. oil in water emulsions) tas been studied. It has been found that the Partec laser backscatter instrument provides reasonably accurate and reproducible results when used to characterize opaque, highly reflective particles such as hydrated alumina, but suffers from a lack of sensitivity to fine transparent particles such as oil droplets. The instrument does, however, readily detect the presence of opaque particle contaminants in oil‐water emulsions.
Size and Velocity Measurements of Large Drops in Air and in a liquid‐liquid two‐phase flow by the phase‐Doppler technique
Authors: Haugen Per , Hayes Edward I. , von Benzon Hans‐Henrik
Published: December 2004

Particles comparable in size to or larger than the measurement volume need extra consideration when measured by a phase‐Doppler system. The phase of the Doppler burst received when such particles traverse the measurement volume depends not only on the size of the particle but also on its trajectory, since the particle is not uniformly illuminated. This paper presents a strategy for securing correct measurements even under such conditions, taking advantage of the three‐detector receiving optics of the Dantec Particle Dynamics Analyzer. The effectiveness of the approach is demonstrated for sizing drops in liquid‐gas and liquid‐liquid two‐phase flows: water drops in air, water drops in FC72 and FC72 drops in water. The combination of water and FC72 is also of interest because the relative refractive index is close to unity. Measurements of drops size were made on a monodisperse stream of drops about 2 mm in diameter, i.e. substantially larger than the measurement volume, and polydisperse distributions of drops ranging in diameter from below 0.2 mm to about 1 mm.
Performance Evaluation of Different Phase‐Doppler Systems
Authors: Domnick Joachim , Dorfner Vitus , Durst Franz , Yamashita Masami
Published: December 2004

The results of comparative measurements of three different phase‐Doppler systems applied to a steady‐state water spray are discussed. The three receiving systems, i. e. DANTEC 57X receiving optics with covariance processor, an AEROMETRICS fibre‐based receiver with DSA processor and standard INVENT phase‐Doppler extension, were used with a 2‐D fibre‐optics‐based transmitting system. A constant scattering angle of 70° was chosen, which is near the Brewster angle for water. Measurements were taken in the spray cone of hollow‐cone pressure atomizer at two different axial distances from the nozzle. Local size distributions, size/velocity correlations and the mean diameters D10 and D32 were compared. The results indicate very good agreement between the different systems, especially with respect to the mean diameters. Larger scatter of the results occurs for the measured volume flow rates, but the calculated mean volume flow rates coincide fairly well with the nominal flow rate of the atomizer.
Optimum Seeding Particles for Successful Laser Doppler Velocimeter Measurements
Authors: Ikeda Yuji , Nishigaki Masashi , Ippommatsu Masamichi , Nakajima Tsuyoshi
Published: December 2004

Seeding particles for laser Doppler velocimeter (LDV) measurement have been developed which are of uniform diameter, spherical shape, low loose weight and high melting temperature. Evaluation test results show that the use of the particles can increase the signal quality substantially and extend the measurable field of the LDV, which can hardly be accessed by conventional measurement methods.
Determination of Particle Size Distribution by the analysis of intensity‐constrained multi‐angle photon correlation spectroscopic data
Authors: Wu Chi , Unterforsthuber Klaus , Lilge Dieter , Lüddecke Erik , Horn Dieter
Published: December 2004

Laser light scattering (LLS), especially dynamic laser light scattering (DLS), also known as photon correlation spectroscopy (PCS), is a well established method for particle size distribution analysis. It usually involves a Laplace inversion of the field autocorrelation function. However, the resolution is limited because of the ill‐conditioned nature of this Laplace inversion. No unique solution exists when noise is present on the data. In contrast with this ill‐conditioned nature, the angular dependence of scattered (static) intensities is precisely not ill‐conditioned, which allows the resolution of the ill‐conditioned inversion of DLS data to be improved. In order to characterize samples with more complicated size distributions, an intensityconstrained multi‐angle PCS data analysis program has been developed, which is an alternative way of normalizing the field correlation function to that reported by Cummins and Staples [12]. In this program, the field autocorrelation function is normalized to the scattering intensity by using a predetermined coherent factor at each angle, which provides an additional constraint on the Laplace inversion of multi‐angle PCS data analysis. The alternative analysis improves the resolution of PCS and provides a more reliable particle size distribution than single‐angle data analysis. Both simulated and measured LLS data are used to illustrate its application, resolution and limitations.
Optical Multiple Scattering by Particles
Authors: Ishimaru Akira
Published: December 2004

When an optical beam is incident on particles that are randomly distributed, and if the fractional volume is small, single scattering theory is adequate to explain the scattering characteristics of the medium. However, when the fractional volume is increased, multiple scattering effects cannot be ignored. This paper reviews the fundamental theories of multiple scattering including radiative transfer and diffusion theories. Also included are recent studies on polarization effects, localization, enhanced backscattering, resonant localization, pulse scattering and scattering in dense media.
New Computational Techniques to Simulate Light Scattering from Arbitrary Particles
Authors: Hoekstra Alfons G. , Sloot Peter M. A.
Published: December 2004

The coupled dipole method, as originally formulated by Purcell and Pennypacker [3], is a very powerful method to simulate the elastic light scattering from arbitrary particles. This method, however, has one major drawback: if the size of the particles grows, or if scattering from an ensemble of randomly oriented particles has to be simulated, the computational demands of the coupled dipole method soon become too high. This paper presents two new computational techniques to resolve this problem. First the coupled dipole method was implemented on a massively parallel computer. The parallel efficiency can be very close to 1, implying that the attained computational speed scales perfectly with the number of processors. Second, it is proposed to reduce the computational complexity of the coupled dipole method by including ideas from the so‐called fast multipole methods (hierarchical algorithms) into the coupled dipole method. In this way calculation time can be decreased by orders of magnitude.
Extinction of Radiations in Sterically Interacting Systems of Monodisperse Spheres. Part 1: Theory
Authors: Riebel Ulrich , Kräte Udo
Published: December 2004

So far, the evaluation of extinction measurements has mostly relied on Bouguer‐Lambert‐Beer's law (BLBL), even though BLBL is known to be valid in the limit of low concentrations only. With higher particle concentrations, particle‐particle interactions such as multiple scattering, dependent scattering and steric interactions can lead to important deviations from BLBL. In a discussion of the various interaction mechanisms, steric interactions are shown to be dominating in a wide and practically important range of parameters. For the theoretical description of steric interactions, different complementary models are introduced, including a statistical model, a layer model and a numerical simulation model. The various approaches coincide to yield a simple extinction equation in two versions, applying to the regimes of Fraunhofer diffraction and straight ray propagation, respectively. In any case, BLBL is found as the low concentration limit of the extinction equation. All considerations are restricted, so far, to the case of monodisperse spherical particles.
Diffraction Patterns of Static Particles on a 2‐D Surface
Authors: Cao Jing , Watson David
Published: December 2004

The diffraction patterns of static particles deviate from those of dynamic particles of the same distribution characteristics. Use of diffraction solutions based on independent scattering to analyse such diffraction patterns leads to a narrower size distribution biased towards the smaller sizes. A 2‐D coherent diffraction model using an inter‐particle relation PDF function is developed. The model clearly demonstrates the terms due to the individual particle diffraction and the terms contributed by the inter‐particle correlation, i.e. the coherent effects. The deviation of the static particle diffraction pattern from that of the dynamic particles can be well predicted. The results of this study provide a general solution for utilizing the forward diffraction technique in static particle measurement. One of the important applications of the new model is in the development of a diffraction reference reticle used for diffraction‐based particle sizing instruments verification.
Characterization of Particulate Mixtures by In‐Line Measurments
Authors: Weinekötter Ralf , Reh Lothar
Published: December 2004

The quality of particulate mixtures influences strongly the efficiency of downstream process steps. The design or optimization of mixing processes requires fast and accurate methods for determining mixture quality. This paper describes an optical method for the in‐line concentration measurement of the key (tracer) component in particulate mixtures with fiber optical probes. Small fluctuations of tracer concentration equivalent to a low concentration variance represent a high degree of mixing. Monochromatic light penetrates via fiber optical probes into a powder sample. A photometer measures the intensity of the diffuse reflected light. If the tracer differs in colour from the other components of the mixture its concentration can be determined. Three types of fiber optical probes were tested. For calibration two series of mixed samples covering a broad concentration range were prepared, one consisting of white Al(OH)3 and dark SiC and the other of Al(OH)3 and a much finer green pigment. The calibration graphs are described by the Kubelka‐Munk theory. The influence of changes in particle size on the signals is reduced by choosing a probe with an angled arrangement of the fibers. The sample mass of the probes is estimated to ca. 0.01 g, based on comparison with random mixtures at different tracer concentrations. In‐line measurements provide extensive data sets which allow advanced statistical intepretations of mixing processes.
Relevance of Reflection in Static and Dynamic Light Scattering Experiments
Authors: Van Der Meeren Paul , Vanderdeelen Jan , Baert Leon
Published: December 2004

Using a monodisperse PMMA dispersion, it was shown that light reflection at the sample cuvette walls may greatly influence the results of both static (SLS) and dynamic (DLS) light scattering experiments. Considering SLS, this reflection phenomenon mostly causes an overestimation of the scattered intensity at high scattering angles, which may give rise to the emergence of an additional, artificial peak in the lower region of the particle size distribution. On the other hand, the influcence of reflection on DLS measurements was shown to be particularly important in the upper region of the particle size distribution. The experimentally observed phenomena were explained from the basic principles of both particle sizing methods. Finally, it was shown that the disturbing effect of reflection could be avoided by modifying either the hardware or the software of the static and dynamic light scattering technique.
Some Far‐Field Scattering Characteristics of Radially Inhomogeneous Particles
Authors: Kai Li , Massoli Patrizio , D'Alessio Antonio
Published: December 2004

The finely stratified sphere model was used to calculate scattered electromagnetic fields from radially inhomogeneous spherical particles illuminated by electromagnetic plane waves. The calculation results show that radial gradients of the real part of the refractive indices change the ray paths into curved lines inside large spherical particles, resulting in fluctuations of rainbow positions for droplets during heat transfer processes. The light intensity in the forward scattering region is found to be useful to infer information about the profile of the imaginary part of the refractive index.
Determination of Geometrical Properties of Mechanically Delaminated Ultrathin Talc Platelets
Authors: Ishimori Toshihiro , Yamashita Mika , Senna Mamoru
Published: December 2004

The three‐dimensional particle size and shape of mechanically delaminated talc thin platelets were determined by combining two different methods. The plate diameter was determined by microscopy with the aid of an image analyser and the thickness from the X‐ray crystallite size perpendicular to the basal plane. The net line broadening of the X‐ray diffraction peak, necessary for the determination of X‐ray crystallite size, was evaluated by electron microscopy. In order to correct X‐ray diffractometry for instrumental broadening, the platelet thickness of a representative specimen was obtained directly using a transmission electron microscope coupled with a laborious slice technique with an ultramicrotome.
Application of Fractal Geometry in Quantitative Characterization of Aerosol Morphology
Authors: Lee Chung‐Te , Chou Charles C.‐K.
Published: December 2004

The aerosol morphologies of six types of particles plus one other from a different source were characterized quantitatively in terms of fractal dimensions based on boundary, projected area and surface roughness. Except for the particle with a smooth boundary, multifractal features were observed on the projected boundary of aerosols. It was found that the fractal dimensions of the aerosol boundaries in the high‐resolution region ranged from 1.00 to 1.13, whereas those in the low‐resolution region were distributed from 1.04 to 1.91. The compactness of a particle could be examined in terms of the fractal dimension of its projected area such that a solid particle gave a value of 2.00, a hollow particle with pores inside gave a value of 1.93 and a chain agglomerate gave an even lower value of 1.81. Aerosol topological features retrieved from the gray levels of a microimage were used to illustrate the difference in surface roughness or distinguish particle deposition on the substrate from that of agglomeration. A value of 2.49 was found for a hollow sphere in contrast to a value of 2.26 for a round pollen particle. Finally, a coordinate system was established by employing the computed fractal dimensions as axes to accommodate the particles characterized in this work and the Euclidean distance of a point from the origin was shown to be a potential composite index for aerosol morphology.
Monodispersion of the Investigated Flow in the Sorting Unit of a particle size optical and electrical analyser
Authors: Ovod Vladimir
Published: December 2004

The use of a compact cylindrical piezoelectric transducer in the jet dispersion unit of the sorting system of an optical or electrical particle size analyser is discussed. Solving two equations for the shift distribution in a piezoelectric transducer with a running fluid chamber, important expressions for the vibrational velocity of acoustic terminal, mechanical impedance, of the stable part of the jet are obtained. The practical application of this technique is illustrated by the calculation of desi parameters for an industrial dispersion unit used in an H.cytophotometer (Ortho Instruments, USA). Good agreement between theoretical and experimental results is shown.
Modified glow discharge spectroscopy for surface analysis of steels
Authors: Ohashi Yoshiharu , Yamamoto Yasuko , Tsunoyama Kozo , Kishidaka Hisashi
Published: December 2004

Grimm‐type glow discharge spectroscopy (GDS) was installed and evaluated as an emission spectroscopic source for the analysis of steel surfaces and for the determination of in‐depth concentration profiles. In order to restrict the abnormal intensity fluctuation at the surface layer, which was observed during analysis of 300 Å of the sample surface layer, the third electrode was installed in the light source and a preliminary discharge technique was developed. The purpose of this preliminary discharge is to clean the sample surface and inner wall of the anode pipe, and to produce plasma in the discharge chamber in order to start the main discharge smoothly. By using GDS with this technique (modified GDS) the influence of abnormal fluctuation at the first stage of discharge was completely excluded and the unstable region of the intensity profile at the beginning of discharge was restricted to 10 Å or so. This modified GDS was applied to the analysis of the surface of box‐annealed steel sheets and the determination of changes in composition with depth below the surface. The results were confirmed by an investigation of the in‐depth analysis of the same samples previously conducted with an ion microprobe mass analyzer (IMMA), and this fact revealed the usefulness of modified GDS as a surface analyzer.
Stress distributions and thin film mechanical properties
Authors: Hoffman R. W.
Published: December 2004

Non‐uniform stresses exist near the edges of thin films as a result of satisfying the boundary conditions. Growth stresses also contribute to stress gradients within the film, especially in structures with a void‐columnar microstructure. As a result the strain‐sensitive properties also must show spatial variations which will become more important as the specimen size decreases. We examine the origin of these distributions within the limits of elestic behavior, and discuss cases for which the distributions have also been measured. The role of plastic deformation in relaxation and fracture is introduced.
Evaluating ratio data for the determination of reduced thicknesses by XPS
Authors: Ebel Maria F.
Published: December 2004

XPS investigations of surfaces with overlayers of thicknesses smaller than 10 nm provide photoelectron spectra from the substrate and the overlayer. For determination of the reduced thickness of the layer it is most valuable to employ a ratio of integrated line intensities (nlayer/nsubstrate). The theory of the ratio method results in a ‘two unknowns’ problem (reduced thickness and a constant). For SiO2 on Si the constant is well known (0.67) and thus the thickness of the layer can be obtained by a measurement performed under one take‐off angle. Other experimental situations demand measurements under different take‐off angles and a least‐squares fit. It is shown how surface roughness influences the application of equations derived for ideally smooth surfaces. The use of these equations for photoelectrons with great differences in their energies is demonstrated.
Scanning Auger microscopy: Resolution in time, energy and space
Authors: Brooker A. D. , Castle J. E.
Published: December 2004

For the examination of dynamic experiments using scanning Auger microscopy, it is important to achieve optimum resolution in time, energy and space. For example, to study a solidification front moving through a pool of molten metal, time resolution is necessary to allow rapid analysis at the point of freezing (allowing perhaps compositional data to be included on a phase diagram), spatial resolution should be good enough to allow accurate positioning of the electron beam on the front, and energy resolution is needed to distinguish between elements and to determine chemical state information (if it is available).

This work examines a series of pure metal standards using a V.G. Scientific MA 500—a high resolution scanning Auger microscope with a hemispherical analyser. This instrument allows spectra with good signal to noise ratios to be acquired in the pulse counted mode, acquisition being totally computer controlled. Hence the effect of spectrometer variables upon pulse counted spectra has been determined by analysing the standard metals under a wide range of conditions. It has proven possible in a number of cases, to derive relationships between the spectrometer conditions (which are under operator control) and the resultant spectra. From these relationships ‘resolution diagrams’ may be constructed, which define the acquisition conditions necessary to achieve the chosen resolution in any of its three modes. It is felt that the approach used in the construction of such diagrams could be used for any spectrometer configuration.
The quantitative measurement of Auger peaks in N(E) form
Authors: Underhill P. R.
Published: December 2004

It is pointed out that for highly accurate measurements, it is important that the standards and unknowns have similar elemental distributions over the escape depth of the Auger electrons. This requires that the total Auger spectrum, including no‐loss peak and low energy loss background be the same for the unknown and standards spectra. In this case, linear least‐squares fitting of the total electron spectrum about the Auger peak in the unknown spectrum, with standard spectra and an extra arbitrary straight line produce fast, accurate, statistically‐meaningful results.
Chromium chromate as an inert marker in copper oxidation
Authors: Day Robert J. , Frisch Margaret A.
Published: December 2004

Chromium chromate films applied to commercial copper foil as corrosion inhibitors are observed to move into the copper during heat treatment in air such as occurs during lamination of printed circuit boards. Chromium depth distributions measured using secondary ion mass spectrometry for foils heated at various times and temperatures show that this change in position of the chromium is not a result of diffusion of the chromium compound. Rather, the major phenomenon is outdiffusion of copper driven by its oxidation at the surface. The temperatures examined spanned one region in which copper oxidation was the rate limiting factor in the overlayer growth and a second region in which growth of the copper oxide overlayer was diffusion limited. Implications in circuit board manufacturing are discussed.
Variable angle XPS investigation of lubricant films coated on sputtered carbon
Authors: Swami G. T. K.
Published: December 2004

The thickness t of the fluorocarbon lubricant applied on the sputter‐deposited carbon substrates is measured using the uniform overlayer model

where γc is the mean free path of the C 1s photoelectrons in the lubricant, R is the experimentally measured intensity ratio of the fluorocarbon to the hydrocarbon components of the C 1s line, θ is the photoelectron take‐off angle, and a is the ratio of C 1s intensity from the lubricant‐free substrate to that from the bulk lubricant. A procedure for experimentally determining the a value, using a partially gold‐coated graphite substrate as a reference, is reported. Values of 4.1, 2.9 and 2.2 were obtained for a respectively on sputter cleaned substrates of graphite, carbon on silicon wafer and carbon on thin film magnetic recording disk. The lower a values of the deposited films are attributed to the presence of voids in the films. Oxidation causes a decrease in a by reducing the carbon content of the substrates, The experimentally determined a values are verifled by monitoring the relative variation in the C 1s and the F 1s signal intensities as a function of θ. The angle dependence of a is discussed.
Characterization of crystal surfaces, thin films and superlattices by brillouin scattering from surface acoustic modes
Authors: Elmiger M. W. , Henz J. , Känel H. V. , Ospelt M. , Wachter P.
Published: December 2004

Surface acoustic waves on single crystals of Ge and Si, thin films of CoSi2 and epitaxially grown CoSi2/Si superlattices on Si (111) are investigated by means of Brillouin scattering. The angular dispersion of the hypersonic surface waves localized at the surface was measured and used to determine the elastic tensor.
Improved dynamic range and automated lineshape differentiation in AES/XPS composition versus depth profiles
Authors: Watson D. G.
Published: December 2004

Depth profiles calculated using simple peak‐to‐peak or peak height or area measurements are subject to inaccuracies caused by spectral noise, sloping backgrounds and possibly by overlapping spectra of different elements or chemical species. An automated program that reduces or eliminates the effects of these potential sources of error in the peak heights and areas calculated from electron spectra has been developed. The program uses linear least‐squares fitting of one or more basis spectra to determine the peak height or area for each spectrum recorded during the profile. The program selects the basis spectra from the energy region data set without operator intervention. The number of unique lineshapes is determined by the program, again without operator intervention, and a profile is calculated for each species. The fit method of intensity determination was found to increase the dynamic range by reducing false contributions to the calculated intensities; this observation holds when a single basis spectrum is sufficient to model the data. Contributions from overlapping spectra are resolved if an example of each pure species lineshape is available in the regional data set. The method is demostrated by practical example.
Theoretical and experimental studies of the broadening of dilute delta‐doped Si spikes in GaAs during SIMS depth profiling
Authors: Badheka R. , Wadsworth M. , Armour D. G. , van den Berg J. A. , Clegg J. B.
Published: December 2004

Delta‐doped structures represent a powerful class of test structures to investigate the experimental and fundamental factors limiting the depth resolution obtainable in SIMS sputter depth profiling.

In this work, theoretical studies of the effects on the broadening of an Si delta spike in GaAs as a function of the energy (1.4–4.4 keV) and angle of incidence (2°, 45° and 60° off‐normal) of the O2 sputter probe beam have been compared with recent experimental data. The theoretical calculations were carried out using the newly developed IMPETUS computer code, which simulates the depth profiling process by taking into account the combined effects of ballistic mixing (treating collisional mixing as a diffusion process), projectile incorporation into the matrix and sputtering. All of these are processes that always occur in any practical sputter depth profiling situation.

The IMPETUS model can reproduce low‐energy Si depth profiles with great accuracy by using the well‐established TRIM calculated range, energy deposition and sputtering data and by making reasonable assumptions for the threshold energy for diffusion in addition to assuming a beam‐ and sputter statistics‐induced surface microtopography, which is described by a Gaussian area versus height distribution having a standard deviation σ = 0.8 nm. Significantly, it is shown that the effects of these parameters on the shape of the sputter profile are largely independent, with σ (accounting for microroughness) mainly affecting the leading edge and the threshold energy (determining mixing processes) the trailing edge of the sputter profile. Good agreement on the energy dependence of the broadening is also obtained. The expected improvement in depth resolution with increasing off‐normal bombardment angle is confirmed and can be quantified. The error in the experimental depth scale calibration based on a constant sputter rate, ignoring transient sputtering, is evaluated. Finally, the sputter depth profile observed for an Si delta spike in GaAs subjected to thermal annealing during growth by molecular beam epitaxy (MBE) can be reproduced accurately by considering diffusion broadening of the initial spike followed by a sputter profiling simulation.
Image depth profiling SIMS: An evaluation for the analysis of light element diffusion for the analysis of light element diffusion in YBa2 Cu3O7–x single‐crystal superconductors
Authors: Gillen Greg , Kaiser Debra L. , Wallace Jay S.
Published: December 2004

An analytical strategy for quantifying the diffusion of 18O in small, melt‐grown single‐crystal Yba2Cu3O7‐x superconductors by image depth profiling SIMS is presented. This technique was used to obtain data for both in‐depth (along the c‐axis) and lateral (in theab‐plane) diffusion from one superconducting crystal. Cross‐sectional images, generated from the image depth profiling data, revealed features of the diffusion processes that would not have been apparent in a standard depth profile. Retrospective selected area depth profiling was used to remove the influence of background species, edge effects and imperfections in the crystals, resulting in processed depth profiles with greater dynamic range. These techniques also were used to study the diffusion behavior of fluorine that was unexpectedly incorporated into the superconduting crystals during preparation. Finally, the influence of detector artifacts on the analytical results was evaluated.
Detection limit for carbon in InSb during SIMS depth profiling
Authors: Galuska A. A. , Greulich F. G.
Published: December 2004

Secondary ion mass spectrometry (SIMS) is commonly used to determine the depth distribution of carbon in semiconductors. Carbonaceous residual gases in SIMS insturumentation and memory effects associated with carbon redeposition within the sputtered craters normally limit the detectability of carbon to ∼ 1 × 1017 C cm−3. In this investigation, the effects of primary ion (Cs+ and O2+), primary ion current (also current density), secondary ion, secondary ion energy discrimination, cryogenic cold finger and vacuum on the SIMS analysis of carbon in InSb were examined and optimized. Under optimized analysis conditions, the detection limit for carbon was reduced to ∼ 1 × 1016 C cm−3. Detection of the 123SB12C− molecular ion rather than 12C− was found to increase the sensitivity to carbon by ∼ 3 ×. In addition, 123Sb12C− was found to be less sensitive to carbon contamination present on as‐received surfaces or incorporated from the analytical environment.
Peak identification for mass spectroscopy
Authors: Lareau R. T. , Buser C. H. , Savin W.
Published: December 2004

Quick, accurate identification of mass spectral peaks is essential, whether the sample is in a gas, liquid or solid state. Often, the mass‐filtered ion spectra include peaks due to atomic, molecular, cluster or multiply charged species. The computer program discussed herein will provide an aid to the mass spectroscopist in identifying: (1) an unknown/interference mass peak; (2) possible overlapping (non‐resolvable) mass species; (3) the required mass resolution necessary to separate neighboring mass species. Other advantages include user selectable species, PC compatible software, unlimited mass range, and unlimited number of variables. Examples will presented for samples analyzed by secondary ion mass spectrometry (SIMS) and glow discharge mass spectrometry (GDMS), as well as indications for its use in general organic mass spectrometry.
The surface photo‐oxidation of polystyrene. Part II: The application of ToF‐SIMS to monitor changes in the surface chemistry of neat polystyrene films
Authors: O'Toole L. , Short R. D. , Bottino F. A. , Di Pasquale G. , Pollicino A.
Published: December 2004

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) has been employed to monitor the chemical changes occurring with continuous UV irradiation in the surface region of neat films of polystyrene and the copolymer of styrene and 2‐(2‐hydroxy‐3‐vinyl‐5‐methylphenyl)benzotriazole (HVB, 2% w/w). Previous conclusions concerning the relative rates of oxygen uptake of these systems have been confirmed. New data are presented that enable delineation of two different surface reactions and demonstrate activation of the polymer surface by HVB with respect to polymer degradation as well as oxygen uptake. Some conclusions are drawn concerning the mechanism by which this activation is achieved.
Optimum parameters for combined Auger‐ionization loss coincidence spectroscopy in the reflection mode
Authors: Gergely G.
Published: December 2004

The detection limit of AES can be improved by combined Auger‐electron loss coincidence spectroscopy (AES‐ILSCS) as proposed by Cazaux. Using an arrangement with two hemispherical analysers and large‐angle collectors, experimental parameters are optimized by (1) matching the energy windows ΔEs of the spectrometers to achieve a large peak/background ratio, (2) setting the angular positions to obtain identical sampling depths for AES and ILS and (3) tilting the sample and using an adjustable electron gun at glancing incidence to get a large ILS signal. False coincidence can be reduced by small ΔEs and using very fast detectors in the coincidence mode for post‐accelerated AES and ILS electrons. Based on Langeron's data, the estimated coincidence signal/false coincidence noise ratio is ∼1 for 10−4 Fe coverage on an Si substrate using 9 keV, 10 nA primary electrons and a Δt ≈︁1 ns coincidence interval. The detection limit can be improved by a factor of 102 with respect to conventional AES.
Improved images with the scanning photoelectron microscope at the national synchrotron light source
Authors: Ade Harald , Ko Cheng‐Hao , Johnson Erik D. , Anderson Erik
Published: December 2004

We present recent developments with the scanning photoelectron microscope at beam line X1A (X1‐SPEM) at the National Synchrotron Light Source. It was the first to demonstrate elemental and chemical imaging with primary photoelectrons and achieve submicron resolution [Appl. Phys. Lett. 56, 1841–1843 (1990)]. Subsequent improvements allow us now to acquire XPS images with lateral resolution approaching 0.1 μm. We have utilized the instrument to examine artificial structures such as microelectronic devices and describe here our preliminary work in the study of photon‐beam‐mediated chemistry on aluminum surfaces.
An investigation of surface segregation in magnetron‐sputtered NbSi using UPS and AES
Authors: Hucknall P. K. , Walker C. G. H. , Greig D. , Matthew J. A. D. , Norman D. , Turton J.
Published: December 2004

Films of amorphous NbSi prepared by magnetron sputtering were found to have a higher concentration of silicon at the surface than in the bulk material. In this paper we report on measurements of both ultraviolet photoemission spectroscopy and Auger electron spectroscopy carried out on samples prepared in situ at the UK Synchrotron Radiation Source, Daresbury. Spectr taken immediately after sputter deposition show that the surface is rich in silicon, while following argon ion bombardment the bulk composition is slowly revealed with a much greater concentration of niobium. This is observed by a comparison of the relative heights of peaks in the Auger spectra and by resonance effects and the sharpening of the Fermi edge in the UP spectra. Of particular interest are changes around the metal‐insulator transition that occur at approximately 11 at.% niobium.
XPS investigation on CoCu mixed oxide catalysts
Authors: Fierro G. , Dragone R. , Moretti G. , Porta P.
Published: December 2004

Metastable and isomorphous cobalt‐copper hydroxysalts with Co:Cu = 100:0, 70:30 and 50:50 atomic ratios have been prepared as precursors by coprecipitation at constant pH from solutions of cobalt and copper nitrates added to a solution of NaHCO3. Mixed oxides were obtained by decomposition of the precursors at 723 K for 24 h in air and in N2. The surface of both precursors and mixed oxides was investigated by XPS. Only Co2+ and Cu2+ species are revealed for the precursors. The mixed oxides present Co2+, Co3+, Cu+ and Cu2+ species depending on the composition and on the calcination atmosphere. Quantitative analysis has evidenced a cobalt enrichment at the surface for the Co:Cu = 70:30 and 50:50 precursors. With respect to mixed oxides, the samples calcined in N2 are characterized by a homogeneous distribution of cobalt and copper both in the bulk and on the surface; in contrast, for the corresponding samples calcined in air the original cobalt enrichment of the precursors is preserved.
Ion‐beam‐induced topography and compositional changes in depth profiling
Authors: Carter G. , Nobes M. J.
Published: December 2004

When energetic ions penetrate and stop in solids they not only add a new atomic constitutent to the matrix but they also create atomic recoils and defects. The fluxes of these entities can give rise to spatial redistribution of atomic components, which may be partly or completely balanced by reordering and relaxation processes. These latter, in turn, may be influenced by fields and gradients induced by the primary relocation processes and by the energy deposited. These will include quasi‐thermal, concentration (or chemical potential) and electrostatic gradients and may act to enhance or suppress atomic redistribution. Some, or all, of these processes will operate, depending upon the system under study, when energetic ions are employed to sputter erode a substrate for depth sectioning and, quite generally, can perturb the atomic depth profile that it is intended to evaluate. Theoretical and computational approaches to modelling such processes will be outlined and experimental examples shown which illustrate specific phenomena.

In particular the accumulation of implant species and defect generation or redistribution can modify, with increasing ion fluence, the local sputtering mechanism and create further problems in depth profile analysis as a changing surface topography penetrates the solid. Examples of such topographic evolution and its influence on depth profiling analysis will be given and models to explain general and specific behaviour will be outlined. The commonality of models which examine both depth‐dependent composition modification and surface topography evolution will be stressed.
Estimation of the grain boundary coverage of segregated impurities from the kinetics of free surface segregation
Authors: Menyhard M.
Published: December 2004

The bulk diffusion coefficient can be determined by measuring the kinetics of free surface segregation. In this paper it will be shown that if one chooses an appropriate temperature and time, the kinetics of free surface segregation mainly depend on the grain boundary diffusivity and the coverage of segregated impurity. In certain cases the grain boundary diffusion coefficient can be considered as known or at least constant and the relative grain boundary coverage can be determined. The average phosphorus coverage on the grain boundary of an FePC alloy will be studied in this way.
SAM investigations of the segregation of sulphur in polycrystalline α‐iron
Authors: Eisl M. M. , Reichl B. M. , Böhmig S. D. , Störi H.
Published: December 2004

Scanning Auger microscopy (SAM) and AES investigations of the segregation of non‐metal impurity atoms (sulphur, nitrogen, carbon and phosphorus) in polycrystalline high‐purity (>99.99%) α‐iron samples were performed in the temperature range 500–800°C. At the beginning of the heating, nitrogen segregates homogeneously and quickly but in the equilibrium state the whole surface is covered with nearly half a monolayer of sulphur. During the first measurements, the segregation of sulphur was ruled by a combined bulk and grain boundary diffusion mechanism with a t1/2 law, resulting in a net‐shaped structure of the surface concentration of sulphur. After repeated heating and sputtering, the contribution of grain boundary diffusion becomes smaller and the segregation rate of sulphur decreases as a consequence of sulphur depletion of the bulk. The segregation kinetics of the individual grains differ strongly owing to the differences between the extent of sulphur depletion of the grains and can be described very well by a t3/2 law in the initial stage of the segregation process. In a later phase, surface diffusion of sulphur from the grains, which have almost reached the equilibrium sulphur coverage, leads to an almost homogeneous sulphur coverage of the surface with only small and diffuse lateral variations.
Alternative model multilayer structures for depth profiling studies
Authors: Zalar A. , Panjan P. , Kraševec V. , Hofmann S.
Published: December 2004

There exists a permanent need for new model systems appropriate for the study of depth profiling with different surface analysis techniques, e.g. AES, XPS and SIMS, which involves the ion sputtering process. The development, preparation, transmission electron microscopy (TEM) characterization and AES depth profiling behaviour of the following new multilayer structures are presented: metal/oxide and oxide/oxide multilayers composed of Ni, Cr, NiO and Cr2O3 thin films and metal/semiconductor multilayers composed of Ni, Cr and Si thin films. These multilayer structures were sputter deposited on smooth silicon substrates and were precisely characterized with AES depth profiling during sample rotation and (two of them) with TEM. The measured compositional depth profiles are explained with respect to the influence of cystalline and amorphous structures on depth resolution, and the advantages of each type of multilayer structure are discussed.
Effects of rotation and ion incidence angle on sputter depth resolution in thin films of NiFe/Ta
Authors: Henneberg Matthias M. , Pocker Daryl J. , Parker Michael A.
Published: December 2004

In an NiFe/Ta system, interface widths (Δz) are compared for sputter profiles with stationary and rotating sample holder (Zalar rotation). For low sputter angles, the Zalar rotation brings considerable improvements in Δz. For higher sputter angles, the improvement available through Zalar rotation vanishes as self‐shadowing due to crystallites with less favorable orientation becomes the dominating rate mechanism. The improvement is further reduced for thinner films much below 1000 Å. For low sputter energies and films 125 Å thick, Zalar rotation has no influence. The limit of depth resolution was 30 Å, which resulted from the substrate‐induced roughness of the NiFe/Ta interface. The interface width's maximum near 30° for stationary sputter etching is characteristic of sputter‐deposited fcc films.