bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of Particle Image Velocimetry to Study Roping in Pneumatic Conveyance
Authors: McCluskey D. R. , Easson W. J. , Greated C. A. , Glass D. H.
Published: December 2004

Particle Image Velocimetry (PIV) is a new technique which provides an instantaneous velocity profile of a flow field. A PIV system at Edinburgh University has been adapted to study the phenomenon of roping in a pneumatic particle conveyance rig. The principle features of this PIV system are as follows. Double images of the particles transported by the fluid are recorded on photographic film using a conventional camera. The displacement of the particle pairs, which determines the velocity at a particular point, is determined to an automatic analysis system. PIV is proving to be a powerful method in the investigation of roping. A rope is a high density ribbon of particles which is created when a uniform air‐coal flow segregates at a pipe bend into two regimes: one has a low coal to air ratio whereas the second regime, termed the rope, has a high coal to air ratio. This particular problem is connected with the pulverised fuel (pf) pipes of coal‐fired electricity generating stations. The flow, as seen on Figure 1, is reproduced in a 26 mm scale model encompassing the main aerodynamic features of pf pipes. The rope forms in the vertical to horizontal 90° bend, falls from the top to the bottom of the horizontal pipe and creats a deposit.
A Single Expression of Common Particle Size Distribution
Authors: Ogawa Kohei
Published: December 2004

A new particle size distribution function based on a simple model is presented. Data generated by the normal, log‐normal and Rosin‐Rammler distribution functions were fitted with this new distribution function and the fitted curves were, for all practical purposes, indistinguishable from all three distributions.

The new distribution function can replace all the three functions and thus a means of presenting and comparing the different size distribution patterns in terms of a single mathematical expression is obtained. Additionally, the new distribution function provides the possibility of developing the discussion on the physical meaning of the particle size distribution.
Characterization of Particle Swelling of Materials of Pharmaceutical Interest
Authors: Caramella Carla , Ferrari Franca , Bonferoni M. Cristina
Published: December 2004

A method based on the employment of an electrical sensing zone instrument (Coulter Counter) has recently been proposed for the combined measurement of the increase in particle volume (particle swelling) and granulometric characterization of pharmaceutical tablet disintegrants. The performance of the method, as far as its applicability to limited swelling materials is concerned, has been assessed. Both inert materials (polystyrene latices) and limited swelling disintegrants (maize starch and crospovidone in different granulometric fractions) were examined for total particulate volume in aqueous media. The accuracy and repeatability of measurements of both total particulate volume and particle volume increase were defined. The results obtained indicate that the method may be adapted for measuring the increase in particle volume of so‐called limited swelling disintegrants.
Lagrangian Stochastic‐Deterministic (LSD) Predictions of Particle Dispersion in Turbulence
Authors: Milojevié Dragoslav
Published: December 2004

A Lagrangian model of particle motion in turbulence has been developed. The model is stochastic in the sense that the "instantaneous" fluid velocity field is generated from known turbulence energy and time scales of large eddies by using a random sampling. The particle motion during the interaction with the eddies is deterministic as being predicted from solutions of Lagrangian momentum equations. On the basis of a large number of calculated trajectories, the distributions of local particle mean and fluctuation velocity components and of the mean square particle displacement are evaluated in a flow domain. The results of the predictions for the case of particle dispersion in nearly homogeneous and isotropic turbulence behind a grid are compared with existing experimental data and satisfactory agreement is achieved. The model is also applied to the case of the particle dispersion from a point source in a nonhomogeneous turbulence of fully developed pipe flow. The agreement with experiments is satisfactory for both heavy and tracer particles. An explanation is given for the experimentally observed phenomenon that in some cases heavy particles disperse faster than fluid points.
Fractal Characterization of Pulverised Materials
Authors: Brown Gareth J. , Miles Nick J. , Hall Steve T.
Published: December 2004

This paper describes preliminary work carried out on the applicability of fractal geometry in describing the products of comminution events.

A nickel sulphide ore was subjected to two comminution events, impact shattering and ball milling. Fractal analysis was performed on samples of the resulting comminution products.

Two differing fractal populations resulted, with the impact sample exhibiting particles having higher boundary fractal dimensions than the milled sample. The fractal dimension of the impact fragments increased with decreasing size, whereas the milled particles displayed a more complex distribution.

The under‐fractal distributions, of the two populations of fragments, generate straight lines when plotted on Gaussian probability paper. This leads to the possibility of being able to predict the distribution of fragments, in fractal terms, of a particular material when subjected to comminution.
Particle Dynamics in an Electrohydrodynamic Flow Field investigated with a two‐component laser‐doppler velocimeter
Authors: Riehle Claus , Löffler Friedrich
Published: December 2004

A laser‐Doppler instrument has been used to measure the migration velocity of NaCl particles in an electrohydrodynamic flow field of an electrical precipitator. The measured average migration velocity of 1.40‐μm particles (number distribution median with a geometric standard devitation of 1.46) is approximately five to six times higher than the calculated steady‐state velocity for a 1.40‐μm particle, provided there is a saturation charge of at least 90f%. Further, the particle velocities in the main flow direction are also influenced by the electrical operation conditions. Both observations demonstrate the important role of the state of the electrohydrodynamic flow field (superposition of moving gas ions and neutral gas molecules) on the particle transport, characterized by the dimensionless electrohydrodynamic number NEHD. A comparison between six different electrohydrodynamic states revealed that NEHD ≈︁ 1 is a critical value for the mutual interactions between the gas ions and the neutral gas phase. Whereas for NEHD values > 1 the stochastic particle motion is chiefly determined by the nonsteady‐state character of the negative corona, for NEHD values < 1 the particle velocity fluctuations are governed by the turbulence level of the neutral fluid. These finding might be helpful in adjusting the operating conditions in electrical precipitators for and optimized particle separation.
The Relevance of Particle Measurement Technology to Process Engineering
Authors: Polke Reinhard
Published: December 2004

To produce disperse products, the characterization of the disperse state and a knowledge of the property function are essential. Property functions are applied not only to characterize the quality of an end product, but also to determine the influence of different processing steps on its state. Hence it is necessary to know the property and process functions for quality assurance of the products and for safety of the processes.

Good laboratory particle measuring technologies are available for investigating property and process functions. On the basis of these functions, process control takes place. On‐line or, better, in‐line measuring techniques are necessary to enable the accompanying process information to be obtained.
Particle Dispersion in Highly Swirling, Turbulent Flows
Authors: Blümcke Erich , Brandt Michael , Eickhoff Heinrich , Hassa Christoph
Published: December 2004

Three‐dimensional transport processes of monosized droplets in a turbulent swirling shear layer were investigated experimentally and theoretically. A model experiment was designed that represents the spray dispersion produced by airblast atomizers. Based on the experimental results, a stochastic dispersion model was developed in the frame of a Lagrangian formulation. Comparison with these experimental data for the dispersion of monosized droplets were made and proved to be satisfactory. The analysis of the remaining differences between calculation and measurement emphasized the importance of an accurate description of gas‐phase turbulence characteristics.
Fractal Dimensions in Data Space; New descriptors for fineparticle systems
Authors: Kaye Brian H.
Published: December 2004

Fractal dimensions in data space are being used to describe fineparticle systems. The relationship between these new parametric descriptions of fineparticle systems and a more classical description of such system using the classical hyperbolic function is discussed. It is shown that fractal dimensions in data space are useful for presenting data for such diverse systems as pigment clusters in composite materials, avalanching powder systems, ballistically fractured material and pore size distribution of porous bodies as determined by mercury intrusion methods. In particular new data is presented on the usefulness of fractal dimensions for describing the flow properties of powders with and without silica flow agents.
Particle Size Distribution Analysis of Industrial Colloidal Slurries using ultrasonic spectroscopy
Authors: Pendse Hemant P. , Sharma Arvind
Published: December 2004

Several solid‐liquid suspensions containing submicron particles at moderate to high concentrations (5 to 50 volume percent) are encountered in industrial slurry processing. Measurements of ultrasonic attenuation spectra are used in a newly developed AcoustoPhor particle analysis system to get particle size distributions of such colloidal suspensions. This paper deals with the performance evaluation of the AcoustoPhor system. The automated ultrasonic spectrometer component of the AcoustoPhor system was tested using a reference silicone liquid for its accuracy and precision. The particle size distribution (PSD) estimation capabilities were evaluated using a set of well‐dispersed slurries covering a wide range of particle concentrations. Sensitivity to process variations was evaluated in field tests at a pigment manufacturing plant. The AcoustoPhor system appears to be capable of providing reliable PSD data for inorganic pigment slurries with particle diameters ranging from 0.01 to 100 micrometers at particle concentrations as high as 50 volume percent.
Tomographic Techniques for Characterising Particulate Processes
Authors: Williams Richard A. , Xie Cheng‐Gang
Published: December 2004

A review of existing and developing process tomographic instrumentation suitable for characterising dry and wet particulate systems is presented. Factors governing the selection of sensing techniques appropriate for static and dynamic imaging of a wide range of single and multiphase particulate processes are discussed. The paper presents a systematic comparison of different image reconstruction methods. Examples of existing, developing and proven applications are cited. Future needs and ways in which these needs can be met are suggested, including the use of multi‐modality methods in which different types of sensing methods are embodied in a single tomographic instrument.
In‐Process Particle Size Distribution Measurements and Control
Authors: Harvill Thomas L. , Holve Donald J.
Published: December 2004

In‐process measurement of particle size and concentration distributions provides continuous analysis and quality control of a product stream. Elimination of sample handling and operator manipulation is now possible for most pneumatic flows using optical methods which are properly interfaced with the process stream.

The EPCS (Ensemble Particle Concentration & Size) described in the following has been used to obtain detailed size distribution measurements in powder production facilities at two second intervals, and has been successfully used for automatic feedback control.
New Generation of Phase‐Doppler Instruments for particle velocity, size and concentration measurements
Authors: Aizu Yoshihisa , Domnick Joachim , Durst Franz , Gréhan Gérard , Onofri Fabrice , Qiu Hui‐He , Sommerfeld Martin , Xu Tien‐Hua , Ziema Maris
Published: December 2004

Phase‐Doppler anemometry (PDA) is applied for particle size, velocity and concentration measurements in two‐phase or multi‐phase flows of ever increasing complexity. For accurate measurements the experimenter must be provided with software and hardware which permit an optimal layout of the PDA optics for a given application, reliable detection of signals over a wide particle diameter range, accurate determination of particle concentration and precise discrimination between particles of different composition. Recent work at LSTM, Erlangen, has been directed to developing a complete PDA package for the above purposes. Progress in this direction is summarized in this paper.
The Phase‐Doppler Method Applied to Very Small Particles
Authors: von Benzon Hans‐Henrik , Buchhave Preben
Published: December 2004

Using a computer model based on Lorenz‐Mie and generalized Lorenz‐Mie theory, various optical confiugurations of a phase‐Doppler system were analysed with regard to their suitability for diameter measurements in the sub‐micron range. The major concern in this size range is multi‐valuedness of the phase‐diameter characteristic, the relatively small signal‐to‐noise ratio obtained with the very low scattered intensity and the small value of the phase difference to be measured. It is shown numerically and by experiment that for particles in a free stream the multi‐valuedness and the shot noise need not prohibit measurements in the sub‐micron size range. The major source of phase error results from light scattered form objects or material other than the particle inside the measuring volume. Using an optical set‐up with nearly counter‐propagating incident beams and a large angle between the detectors, measurements were obtained for particle diameters down to 200 nm, and it is estimated that with some improvements in receiver optics measurement down to 100 nm will be possible.
The Phase Doppler Method: Analysis, performance evaluations, and applications
Authors: Bachalo William D.
Published: December 2004

This review of the recent developments in the phase Doppler method provides information on the advances made to the method and delineates some potential error sources. Methods used to eliminate these potential error sources are also discussed. It is shown through comparison to the Lorenz‐Mie theory and the GLMT that the geometrical optics theory offers a reliable and efficient computational tool for the analysis of the light scattering with the phase Doppler method. The geometrical optics theory was then used to optimize the measurement parameters in the system designs and a significant reduction in the measurement uncertainty was realized. Limitations on the particle concentrations in which the instrument will operate reliably are also addressed. A brief discussion of the instrumentation and, in particular, the signal processing is presented. The advantages in using the Fourier transform approach are discussed. As a demonstration of the capabilities of the instrument, several performance tests were reviewed and examples of the application to spray combustion and turbulent dispersion of particles are given.
Response of Laser Diffraction Particle Sizer to Anisometric Particles
Authors: Gabas Nadine , Hiquily Noël , Laguérie Claude
Published: December 2004

This study deals with the size measurement of non‐spherical particles by the laser diffraction technique. Size analyses of three sets of identical metallic bodies (cubes, tablets and cylinders) were performed by means of a Malvern 2600 instrument. The results prove that under the operating conditions chosen and in the case of anisometric objects, the mean total surface area is not measurable either because the Malvern software, strictly valid for spheres, is not applicable to such particles or because the particles adopt preferential orientations in the measurement cell. Further, a way of processing diffraction data is proposed in order to determine two characteristic dimensions of identical anisometric particles. It is based on the measurement of the minimum and maximum projected surface areas of the particles. The experimental results obtained with our particles show the procedure to be reliable.
Trajectory Ambiguities in Phase Doppler Systems: Study of a near forward and a near‐backward geometry
Authors: Gréhan Gérard , Gousebet Gérard , Naqwi Amir , Durst Franz
Published: December 2004

Generalized Lorenz‐Mie theory for the scattering of arbitrarily shaped beams by spherical particles has been applied to two standard phase Doppler layouts, employing receiving units at 30° and 150° off‐axis locations. It is shown that the particle trajectory effects may lead to inaccurate size measurements for the near‐forward receiver and may make the near‐backward measurements totally misleading when a large particle size range (1:40) needs to be covered. Only limited improvements can be achieved by using two phase‐shift signals from a single receiving unit for discrimination. The errors associated with the trajectories are also detrimental to the concentration measurements based on the existing criteria. However, an extended optical system employing two identical receiving units, located symmetrically about the plane of the laser beams, provides a robust solution to the trajectory ambiguity. It can be used to measure correctly the particle size and the particle location in the measuring volume. The difficulties associated with estimating the effective size of the measuring volume as a function of the particle diameter (in order to determine the true size distribution and the particle number density) may also be resolved by employing an extended system. Hence, despite a higher cost, this arrangement is attractive, at least for obtaining some benchmark simultaneous measurements of sizes and velocities in two‐phase particulate flows.
Particle Breakup in Shock Waves Studies by single Particle Light Scattering
Authors: Strecker Jörgt J. F. , Roth Paul
Published: December 2004

The breakup of suspended, agglomerated submicron particles was studied by exposing the aerosol to weak shock waves of varying strength under conditions 400 ms−1⩽v⩽880 ms−1. A newly developed laser light‐scattering diagnostic employing a top hat laser profile was used to size the particles passing through a very small scattering volume. By Comparing the optically measured particle size in front of and behind shock waves, the breakup of agglomerated particles could be clearly identified. The experiments indicate that the aerodynamic forces behind an incident shock overcome the particle binding force resulting in disintegration of the submicron agglomerates. The results are presented in form of a modified Weber number.
Influence of the Measurement Volume on the Phase Error in Phase Doppler Anemometry. Part 1: Reflective mode operation
Authors: Albrecht Heinz‐E. , Borys Michael , Wenzel Marcus , Wriedt Thomas
Published: December 2004

In phase Doppler anemometry (PDA), phase difference errors are caused by the Gaussian intensity distribution of the laser beam and the curvature of the phase fronts outside of the beam waist. This results in erroneous particle sizes. Based on a physical analysis by geometrical optics [1], this phase difference error is evaluated for reflected mode operation (Part I) and for refracted mode operation (Part II). By varying the particle trajectories statistically, the error in determining the particle size and the mass flow can be simulated. By the method described the error in the measured phase difference can easily be estimated.
Quasi‐Self‐Preserving Log‐Normal Size Distributions in the Transition Regime
Authors: Otto Eckhard , Stratmann Frank , Fissan Heinz , Vemury Srinivas , Pratsinis Sotiris E.
Published: December 2004

A log‐normal model, based on the extended SIMPLER‐algorithm utilizing the Modal Aerosol Dynamics Modelling Technique, and a sectional model are compared for Brownian coagulation in the transition regime. The models are in good agreement with respect to the calculated particle size distribution moments. Applying the log‐normal model a simple coagulation model consisting of a closed set of five equations is developed that does not require the solution of ordinary diferential equations.
Interaction of Annular Air Jet with a Non‐Evaporating Liquid Spray
Authors: Friedman Jacob A. , Renksizbulut Metin
Published: December 2004

The effects of a concentric annular air jet on the structure of a liquid spray have been examined under isothermal conditions using Phase Doppler interferometry, and flow visualization techniques. Local measurements of drop size, velocity, volume flux, and number density have been made simultaneously and non‐intrusively. The results show that the initial spray cone widens substantially with increasing air flow while the overall spray envelope remains essentially the same. The air jet creates a narrow high mass flux region of small droplets in the core of the spray, surrounded by a nearly uniform flux region extending almost to the boundary of the spray. Line averaged mean diameters are found to be slightly smaller, indicating that the annular air jet plays a role improving the atomization process as well.
Characterizing the Rheology of Powders by studying dynamic avalanching of the powder
Authors: Rastogi Saurabh , Klingzing George E.
Published: December 2004

Avalanching of solids is an important multivariable dependent phenomenon that can be a valuable tool for characterization of solids flowability. Although avalanching by itself is primarily chaotic it appears that the fractal analysis of its avalanching mass data can yield very interesting and significant information that is of importance in determining suitability of a material in solids handling and pneumatic transport.
Application of Regression Analysis in spectroturbidity size‐characterization methods
Authors: Vavra Jozef , Antalik Jozef , Liška Marek
Published: December 2004

The possibilities of applying specific turbidity and turbidity theoretical computations of light‐scattering characteristics, the ratio methods in the distributional analysis of PVC and SiO2 exact Lorenz‐Mie theory was applied. A good correlation with dispersions with spherical particles are discussed. The calculation of the best estimates of distribution function parameters was found were performed numerically using the simplex method. For theoretical computations of light‐scattering characteristics, th exact Lorenz‐Mie theory was applied. A good correlation with the results of angular light scattering and electron microscopy was found.
An appraisal of the present position and future potential of inelastic electron tunnelling spectroscopy (IETS)
Authors: Shott P. N. , Field B. O.
Published: December 2004

The present position regarding the preparation of junctions suitable for IETS investigation and the various doping procedures is outlined, and a comparison is drawn between IETS and other surface spectroscopies. A survey of the systems already studied of interest in the fields of surface chemistry, heterogeneous catalysis, analytical chemistry and environmental pollution monitoring, adhesion science, radiation damage, biological chemistry and electronic energy level studies is presented. The parameters thought to affect the development of this technique and some potential applications to corrosion inhibitors and metal protection, lubrication studies, solid‐state devices and photochemical energy converters are considered.
Examination of contamination on electrical insulators by XPS
Authors: Drummond I. W.
Published: December 2004

A method is described which allows samples to be taken form the surface of electrical insulators which suffer electrical breakdown. The insulator does not have to be removed form its immediate environment. The contaminant is removed by ‘stripping’ it off with adhesive tape and the tape is subsequently examined by XPS.
Reference levels in electron‐excited and X‐ray‐excited Auger spectra
Authors: Wagner C. D. , Taylor J. Ashley
Published: December 2004

Auger spectroscopy and X‐ray photoelectron spectroscopy have evolved using different reference levels for electron energy measurement. Electron‐excited Auger spectra are referenced to the vacuum level, and X‐ray‐excited Auger spectra are referenced to the Fermi level. This can cause confusion, especially when both are recorded in the N(E) mode in the same instrument.
Secondary ion mass spectrometry/X‐ray photoelectron spectroscopy study of CO adsorption on Ni and of Fischer–Tropsch synthesis on FeRu alloys
Authors: Fleisch T. , Delgass W. N. , Winograd N.
Published: December 2004

The adsorption of CO on a Ni(100) single crystal surface has been investigated by X‐ray photoelectron spectroscopy and static secondary ion mass spectrometry. At room temperature CO chemisorbs molecularly on Ni. A saturation coverage of about 0.5 monolayer is reached after 2 L CO exposure. The NiCO+/Ni2CO+ratio increases from very low values at low coverage to a saturation value of about 4.5. Dynamic studies of Ni+and NiCO+yields during exposure to 1.3 × 10−6to 1.3 × 10−5Pa of CO show reversible pressure and temperature dependent changes in addition to chemisorption. We ascribe these effects to CO weakly adsorbed on both the clean and CO‐covered Ni surface. The interaction of CO and H2with FeRu alloy surfaces has been studied by XPS and SIMS as well as by kinetic measurements. Fe surface enrichment is observed which explains the catalytic behavior of the alloys in Fischer–Tropsch synthesis (FTS). Ru rich surfaces remain unchanged during FTS but an extensive and rapid carbon build‐up is found on the alloy surfaces. Silica supported alloys coke more slowly. The carbon build up on pure Fe is preceded by a carbide formation that coincides with a maximum in hydrocarbon synthesis activity. Potassium promoted Fe exhibits a faster carbon deposition than pure Fe, but the potassium appears to stay on the uppermost surface by diffusing through the carbon layers.
Semiconductor crystal growth by sputter deposition
Authors: Greene J. E. , Eltoukhy A. H.
Published: December 2004

Recently, understanding of the physics of ion–surface interactions has progressed sufficiently to allow sputter deposition to be used as a crystal growth technique for depositing a wide variety of single crystal elemental, compound, alloy, and superlattice semiconductors. In many cases, films with essentially bulk values of carrier concentrations and mobilities have been obtained. The controlled use of low energy particle bombardment of the growing film during sputter deposition has been shown to affect all stages of crystal growth ranging from adatom mobilities and nucleation kinetics to elemental incorporation probabilities. Such effects provide inherent advantages for sputter deposition over other vapor phase techniques for the low temperature growth of compound and alloy semiconductors and are essential in allowing the growth of new and unique single crystal metastable semiconductors. This review includes sections on the physics of sputtering, experimental techniques, and ion bombardment effects on film growth as well as a discussion of recent results in the growth of elemental, III–V, II–VI, IV–VI, metastable, and other compound semiconductors.
Experimental study of matrix effects in quantitative auger analysis of binary metal alloys
Authors: Mathieu H. J. , Landolt D.
Published: December 2004

The importance of matrix effects in quantitative AES is investigated by comparing experimental results with theory. Experimental AES amplitude ratios are presented as a function of composition of five different binary alloy systems Ni–Mg, Ni–Pd, Ag–Pd, Mo–Fe and Cr–Fe. Contamination free surfaces were produced by fracturing in situ under UHV conditions. Matrix correction factors were evaluated applying literature data and considering the influence of atomic density variation, of the escape depth of Auger electrons and of backscattered electrons. The influence of the matrix is large only for alloy components differing widely in density and atomic number. Comparison of calculated with experimental data reveals that agreement can be achieved within 2–15% depending on the alloy system considered.
A new approach to surface energy characterization for adhesive performance prediction
Authors: Penn L. S. , Bowler E. R.
Published: December 2004

A new approach to qualitatively predicting adhesion at a solid/solid interface is described. It is based on thermodynamic compatibility of the two adhering surfaces, but it overcomes the weaknesses of existing methods by using a full set of contact angle data and by assembling the data to reveal the main features of the set without loss of information. Adhesive performance data to support this approach are presented.
A contribution to the investigation of enamel/metal Interfaces
Authors: Baumgartl S. , Warnecke W. , Holm R.
Published: December 2004

The diffusion processes which influence the adhesion between enamel and metals take place in an ∼5 μm thick layer at the interface. Electron X‐ray microanalysis cannot be used to investigate this zone, except to a limited extent, because its depth and lateral resolution are inadequate. A procedure which permits quantitative determination of Fe in the zone at the interface is described. It is based on X‐ray and Auger microanalysis of tapered sections. The Auger intensities are quantified by X‐ray microanalysis within sufficiently thick enamel layers.
Interfacial reactions between Al and RuO2, MoOx and WNx diffusion barriers on Si
Authors: Hörnström S. E. , Charai A. , Thomas O. , Krusin‐Elbaum L. , Fryer P. M. , Harper J. M. E. , Gong S. , Robertsson A.
Published: December 2004

The Interfacial reactions between Al and RuO2, MoOx and WNx diffusion barriers on Si (100) wafers have been studied. The diffusion barrier structures were analyzed before and after various heat treatments using Auger electron spectroscopy (AES) and cross‐sectional transmission electron microscopy (XTEM). Al was found to reduce the oxides of both Ru and Mo. A 100 Å thick Al2O3 layer developed between the Al and the RuO2 films during annealing at 500°C for 30 minutes. The formation of interfacial Al2O3 efficiently prevents Al penetration but may cause a too high contact resistance for applications in contact structures of microelectronic devices. The WNx barrier was stable after annealing at 600°C for 30 minutes, if the film was exposed to air prior to Al deposition. If, instead, the Al was deposited in situ, the structure failed after annealing at 500°C due to a reaction between Al and W giving WAl12. A thin Al2O3 layer was detected between the Al and the WNx films of the air exposed sample. This layer had the effect of retarding the Al–W reaction and thereby raised the failure temperature of the barrier by at least 100°C.
Characterization of electrodeposited metals using continuous‐wave optical second‐harmonic generation
Authors: Miragliotta J. , Furtak T. E.
Published: December 2004

The optical polarization properties of second‐harmonic generation at normal incidence have been used to characterize the symmetry of electrodeposited monolayers of zinc and thallium on Ag(111) while the sample was under electrochemical control. Our technique involves a non‐conventional‐wave method with standard weak optical signal detection. The overlayers exhibit a strongly bound monolayer phase that can be experimentally separated from the multilayer growth condition. Both metals grow with a C3v symmetry that is aligned with the substrate at low coverage. This is maintained for higher coverages in the case of Tl but changes for Zn. These results are consistent with an epitaxial 8.6% expanded hexagonal monolayer for Zn, followed by a return to the Zn lattice constant at higher coverage. However, we propose that Tl grows with a coincidence lattice that is (6 × 6)–25 Tl for all coverages studied in this experiment (up to five layers).
Electrochemical and XPS evidence of the aqueous formation of Mo2O5
Authors: Clayton C. R. , Lu Y. C.
Published: December 2004

XPS was employed to detect the surface species deposited on an activated platinum electrode following cathodic polarization in deaerated 0.1 M (NH4)6Mo7O24 · 4H2O solution. At – 160 mV (saturated calomel electrode, SCE), evidence was found of the possible dissociation of polymolybdate to molybdate with subsequent surface adsorption. At –340 mV (SCE) molybdate was observed to reduce to Mo5+ in the form of Mo2O5. At – 540 mV (SCE), Mo4+ was the stable species, existing in the form of tetravalent oxyhydroxide MoO(OH)2 according to XPS analysis. No further reduction from Mo4+ to lower‐valent states was observed when cathodically polarized to – 900 mV (SCE). Mo2O5 was found to be unstable in air, oxidizing readily to MoO3.
Applications of secondary neutral mass spectrometry (SNMS) in VLSI technology
Authors: Anderle Mariano , Moro Lorenza
Published: December 2004

Secondary neutral mass spectrometry (SNMS) is a promising analytical technique for the characterization of thin films and bulk samples. We applied this technique to thin films used in VLSI technology.

The samples investigated ranged from sputter‐deposited Al alloy films used as long‐range interconnections, to silicide or silicide/polysilicon structures for gate interconnections, to dielectric films and doped silicon dioxide glasses used for insulation and passivation purposes. In all these samples the distribution of the elements was studied as a function of deposition and/or annealing conditions.

The SNMS results are compared with those obtained by more common analytical techniques, such as SIMS and nuclear analyses (RBS and nuclear reaction analysis). This comparison emphasizes the features of SNMS: good depth information, less sensitivity to matrix effects and optimum depth resolution.
Optical properties of titanium nitride thin films
Authors: Tompkins Harland G. , Gregory Richard , Boeck Bruce
Published: December 2004

Titanium nitride films were deposited using various process parameters. The film stoichiomtery and the optical properties were than measured for all of the films. As expected, the stoichiometry is affected by the deposition rate and composition of the gas phase. We show that the index of refraction is affected by the substrate temperature as well as by the stoichiometry. We also show that as long as the amount of nitrogen in the film is above a critical value, the film is nitride‐like. When the amount of nitrogen in the film drops below a critical value, the index of refraction is more characteristic of metallic titanium than titanium nitride.
Oxide formation on Fe and Ti thin films and on Fe thin films modified with ultrathin layers of Ti
Authors: Lee Paul A. , Stork Kurt F. , Maschhoff Brian L. , Nebesny Ken W. , Armstrog Neal R.
Published: December 2004

Reactions of O2 and H2O to from thin oxides on Fe, Ti and Ti‐modified Fe thin films have been studied by XPS, following O2 and H2O exposure in the range 0‐600 L, to form oxides with thicknesses of < 40 Å. XPS Iineshape analysis is used, utilizing a special combination of reflection electron energy‐loss spectroscopy (REELS) and nonlinear least‐squares fitting routines to model the intrinsic and extrinsic energy losses that accompany potoemission for the Ti and Fe 2p lines. During the formation of the thinnest oxides, this approach yields a unique picture of the composition of the oxide, while for the thicker layers, there is little significant difference between this fitting approach and (1) fitting approaches using an integral background approach or (2) direct deconvolution methods using the REELS data. Both Fe and Ti are quite reactive to O2, yielding a surface oxide that is apparently an FeO‐dominated FeO/Fe3O4 bilayer on Fe surface oxide that is predominantly TiO2 on the Ti surface. Pure Fe and Ti surfaces are unreactive to H2O. Predosing of thewse surfaces with low levels of O2 (5 L) does not increase the reactivity appreciably toward H2O. Ti dispersed on the Fe surface as an adatom layer, with an equivalent thickness of 3 Å, greatly suppresses the reactivity of Fe toward O2, while the Ti is oxidized primarily to TiO2, In contrast to the pure Ti layers, these Ti adatom layers are quite reactive toward H2O, yielding oxides (no evidence for hydroxide) in a uniform distribution of oxidation states (Ti+2, Ti+3 and Ti+4).
Oxidation mechanisms on α‐brasses (10 and 30 at.% Zn) by optical methods and SIMS
Authors: Beucher E. , Lenglet M. , Weber S. , Scherrer S.
Published: December 2004

Optical methods—Fourier transform infrared spectroscopy, ultraviolet‐visible‐near‐infrared spectroscopy (UV‐Vis‐NIR)—are used to control the oxidation products grown on the surface of cold‐worked α‐brasse (10 and 30 at.% zinc). The influence of sample preparation (mechanical polishing and chemical cleanings) on oxidation rates is also studied. The duplex oxide scale (copper oxides on the top of the layer and zinc oxide at the metal/oxide interface) obtained during brass oxidation and perfectly exhibited by SIMS depth profiles can be explained in terms of internal oxidation and of the semiconductor properties of ZnO and Cu2O.
Some Applications of high‐energy, high‐resolution Auger electron spectroscopy using bremsstrahlung radiation
Authors: Kövér L. , Varga D. , Cserny I. , Tóth J. , Tökési K.
Published: December 2004

Continuous energy distribution x‐rays obtained from a high‐voltage (20–30 kV) source with an Mo anode were used for exciting Si KLL, S KLL, Ag LMM and Mn KLL Auger transitions in the 1.5–5.5 keV kinetic energy range. X‐ray‐induced AES measurements were performed by a new, high‐energy electron spectrometer demonstrating the obtainable resolution and the considerable gain in intensity in comparison with previous results.
The intrinsic redox states in polypyrrole and polyaniline: A comparative study by XPS
Authors: Kang E. T. , Neoh K. G. , Tan K. L.
Published: December 2004

X‐ray photoelectron spectroscopy provides a useful tool for the critical comparison of the chemical nature of the nitrogens corresponding to the various intrinsic redox states of electroactive polypyrrole (PPY) and polyaniline (PAN) and their N‐substituted derivatives. Proton modifications of the PPY nitrogens can give rise to a number of intrinsic redox states corresponding to various proportions of the imine‐like (N) and amine‐like (NH) nitrogens, similar to those observed in PAN. For complexes prepared from oxidative polymerizations, the intrinsic oxidation level of PAN is always about twice that of PPY (50% vs. 25%). The behaviours of the nitrogens of the corresponding redox states in both polymers towards oxidation, reduction, protonation and charge transfer interactions are grossly similar. However, the amine nitrogens in the emeraldine (EM) oxidation state of PAN (50% N structure) are more susceptible to protonation in the presence of excess protonic acids than those of the 25% deprotonated PPY (DP‐PPY). Finally, the doping level in poly(N‐methylaniline) (PMAN) is twice that of poly(N‐methylpyrrole) (PMPY). The base polymers of PMAN and PMPY exist only in the fully reduced state and are susceptible to reoxidation. The nitrogens of PMAN, but not PMPY, are also susceptible to protonation.
XPS study of pumice‐supported palladium and platinum catalysts
Authors: Venezia A. M. , Duca D. , Floriano M. A. , Deganello G. , Rossi A.
Published: December 2004

An XPS study has been performed on samples of monometallic catalysts of palladium and platinum and on bimetallic Pd‐Pt catalysts supported on pumice. A negative shift of about 0.5 eV in the Pd 3d and Pt 4f binding energies of the catalysts relative to the energies of the same levels in the pure metals suggested an increase in the electron density in both metals. A quantitative XPS analysis indicated that the supported metals did not modify the surface atomic composition of pumice. In the bimetallic catalysts the variation in the Pd 3d/Pd MNN intensity ratio over the different Pd/Pt atomic fractions has been attributed to surface segregation of the metal present in smaller amount.
Catalytic oxidation of Mo by caesium oxides
Authors: Soriano L. , Trigo J. F. , Galán L. , Rueda F.
Published: December 2004

The oxidation of a clean Mo surface with different caesium oxide overlayers has been studied by means of x‐ray photoelectron spectroscopy. The results show that the presence of a caesium oxide overlayer produces enhanced oxidation of Mo at room temperature when compared with thermal oxidation, and that a layer of MoO3 is formed on top of the Mo substrate. The thickness of this MoO3 layer depends on the thickness of the caesium oxide overlayer. Also, true catalytic oxidation has been observed when the substrate with the caesium oxide overlayer is exposed to oxygen at room temperature. The interface of the MoO3 layer with the Mo metal consists of about five monolayers of Mo suboxide MoOx (with x ∼2) when the oxidation has been performed at room temperature. At moderate temperatures (∼400 K) this interface is smoother, although it tends to decrease in thickness with time. A mechanism of catalytic oxidation that is consistent with the experimental data is proposed. This mechanism is controlled by diffusion of oxygen through the caesium oxide overlayers and through the Mo substrate. Also, a diffusion of Cs towards the surface has been detected. Different phases of the type MoO3−δ can explain the chemical shifts observed in the Mo6+ XPS spectra.
Fine structure of supported and promoted catalysts as deduced from XPS intensity data
Authors: Praliaud H. , Martin G. A. , Fenyvesi J. , Somogyi I. , Varsányi G. , Mink G.
Published: December 2004

For model calculations it is assumed that metal spheroids are randomly distributed on spherical support particles of nearly closest‐packed arrangement. Both the metal and the support can be covered with layers or submonolayers of promoter(s) and carbon. The average diameters as well as n, the average number of metal particles on one support sphere, are estimated from total surface area and selective chemisorption measurements and preferably by electron microscopy too. In the computer programme two cases are distinguished depending on whether n < 4 or n > 4, since in the latter case the partial shadowing of coated metal particles by others should also be considered. Electron beams emitted by the metal, the support and their layers are calculated as a function of the ‘angle of latitude’ of the support spheres and the ‘angle of latitude and longitude’ of the metal spheroids. The computation variables are the thickness and sequence of different layers above the metal and the support, the extent of ‘immersion’ of metal particles into the support and/or its layers and the extent of diffusion of promotor cations into the support matrix. The calculated intensities are compared with the measured ones. By this method the probable fine structure of an alkali‐promoted Pd/SiO2 (n < 4) and a sodium‐promoted Ni/(Al2O3 + SiO2) catalyst (n > 4) has been determined.
A new formalism for angle‐resolved X‐ray photoelectron spectroscopy (ARXPS) and Auger electron spectroscopy (ARAES) of non‐crystalline solids taking elastic electron scattering into account
Authors: Werner W. S. M. , Störi H.
Published: December 2004

The effects of elastic electron scattering in non‐crystalline solids on the angle‐resolved mode of the electron spectroscopic techniques have been studied with a Monte Carlo model. The results of this study demonstrate that elastic scattering must be accounted for in the formalism of angle‐resolved Auger electron spectroscopy and angle‐resolved x‐ray photoelectron spectroscopy. The use of a recently introduced attenuation law for signal electrons in the angle‐resolved electron spectroscopies is studied. The effects of elastic scattering are incorporated in this attenuation law by the use of one additional parameter that depends on the energy and the material. This parameter, the so‐called attenuation parameter, can be found in the literature.

It was found that this new attenuation law yields an accurate description of the influence of elastic scattering on the angular distribution of signal electrons, which is by far superior to the straight‐line approximation. Neglecting the influence of elastic scattering introduces an error of ∼50% in the calculated overlayer thicknesses. The conventional algorithms to restore depth profiles from angle‐resolved experiments can be modified easily to account for elastic scattering through the use of the new attenuation law. This yields restored thicknesses which agree within 1% with the model thickness.

Another important finding of this study for the angle‐resolved electron spectroscopies is that elastic scattering poses a strict upper limit to the depth range that can be analysed by means of angle‐resolved measurements.
Background correction in XPS: Comparison of validity of different methods
Authors: Tougaard S. , Jansson C.
Published: December 2004

We investigate the validity of methods for background correction in XPS by comparing determined peak intensity ratios with theory. For Ag, Pt and Au, peaks are considered for which possible errors in the inelastic electron mean free path and in the energy dependence of the analyser response function have minimal influence on the accuracy of the theoretical ratios. The straight line method gives a root‐mean‐square (RMS) deviation from theory of ∼34% and ∼60% when the low‐energy point is selected to lie close to or far from the main structure of the peak respectively. The Shirley method gives an RMS deviation from theory of ∼35%, with only a small change between two sets of considered energy ranges. The Tougaard method gives an RMS deviation from theory of ∼3%, which is of the order of the expected uncertainty due to the combined effects of the level of the apparatus stability and the errors in the ratios of photo‐ionization cross‐sections.
Quantitative depth profiling of nitrogen‐implanted titanium by use of Auger electron spectroscopy and subsequent target factor analysis
Authors: Bubert H. , Mucha A.
Published: December 2004

Titanium samples were implanted with N+ and N2+ ions of an energy of 80 keV and an ion dose between 1017 and 1018 atoms cm−2, which led to near‐surface nitrogen‐containing coatings. Auger depth profiles were taken from these coatings and the gathered data were subjected to target factor analysis. As a main result, three components could be detected and assigned to metallic Ti, TiN and a hitherto unknown Ti/N component, the atomic concentration ratio of which was estimated to be Ti:N ≈︁ 1:1.15. Thereby, the atomic concentration depth profiles could be calculated, resulting in the stoichiometry of titanium nitride at an implantation dose from 5 × 1017 N+ cm−2 upwards. A relationship between the ion implantation dose and the wear resistance of the coatings could not be corroborated by the measurements.