bluuebunny/crossref_metadata_2025 huggingface dataset:
Capacitor‐Discharge Initiation of a Detonator containing a vacuum‐deposited thin‐film chromium bridge
Authors: Austing James L. , Tulis Allen J. , Hrdina Donald J. , Joyce Richard P. , Urbanski Edward , Fyfe Donald W. , Smith Robert D. , Letendre Guy
Published: December 2004

An experimental program is described in which the capacitor‐discharge initiation characteristics of a detonator containing a vacuum‐deposited thin‐film chromium bridge were studied. The objective of the effort was to define the conditions that would result in overall function times of 10 μs or less. The threshold initiation energy of the detonator was in the range of 11.5 mJ–20.0 mJ. Consistent performance was obtained from a firing energy of 54 mJ, which was achieved by a 5‐μF capacitor charged to 147 V. Under these conditions, the average overall function time was 4.2 μs, with a standard deviation of 0.2 μs. Other tests showed that at higher capacitances and lower voltages the function time increased substantially and became more nonreproducible, even though the stored energy was considerably above the threshold value.
Fragment Generator
Authors: Held M.
Published: December 2004

The design of a fragment generator and the determination of the hit density and of the velocity distribution are described in detail.

From the correlation of the fragment hits on the target plate and the X‐ray flash radiographs it is possible to ascertain the launch angles in the elevation and azimuth directions and, hence, also to determine the true distances the fragments have traveled from the point of detonation of the high explosive charge to the location where the radiograph was taken. In this manner, a precise determination of the velocities of the individual fragments can be made.

In spite of the rather large scatter of the depths of penetration of the cube‐shaped fragments in the mild‐steel target plate, a correlation can be established between the impact velocity and the depth of penetration.
Manufacturing of Multiclads Using a Single Explosive Charge
Authors: Shoukry S. N. , Hegazy A. A.
Published: December 2004

A technique for the fabrication of several mono and/or bimetallic cladded plates using a single explosive charge has been developed at our laboratories. This technique enables the explosive welding of thin plates or foils which are otherwise produced by the rolling of thick explosively cladded plates. This paper describes the technique and lays down the theoretical basis for the determination of the process parameters. It is shown that up to four sheets of 0.5 mm thick stainless steel cladded to 2.0 mm mild steel could be produced using a single explosive charge. The technique was also used for the manufacturing of 8 sheets of 0.25 mm copper foil cladded to 0.5 mm mild steel plate.
High‐performance liquid chromatographic separation of diphenylamine and its reaction products with nitrogen oxides
Authors: De Jong A. L. , Verweij A.
Published: December 2004

Reversed phase high‐performance liquid chromatography (HPLC), using a mobile phase composed of acetonitrile, methanol and water is preferably applied to separate diphenylamine and its major reaction products with nitrogen oxides. This paper describes the evaluation of the preferred chromatographic systems and the application of HPLC to analyse single base propellants.
Investigation of the decomposition processes in double‐base propellants and nitrocellulose under vacuum and oxygen
Authors: Kučera V. , Havránková E.
Published: December 2004

There is described the application of an automated vacuum stability test in following the decomposition and stability of double‐base propellants and nitrocellulose. There is also described a manometric stability test of propellants based on the decomposition in oxygen. This method makes possible to determine small differences of chemical stability and to substitute the time consuming methods based on HPLC.
Corner‐Turning Distance and Retonation Radius
Authors: Held Manfred
Published: December 2004

All high explosives, at least the ones used in military applications, have a specific minimum detonation radius, Rmin with which the detonation can change its direction through 90° or 180°. It is to be emphasized that this applies not only to thc so‐called insensitive high explosives, but the sensitive explosives of course have smaller radii than the insensitive ones.

The corner‐turning distance, As, determined in the radial test, also corresponds to the minimum radius, Rmin for the detonation wave to invert its direction through 180°. The radial test is a simple method, with regard to both design and analysis, that is suitable for determining the 90°‐distance, or the minimum detonation radius, Rmin.
Modeling shock initiation and detonation divergence tests on TATB‐Based Explosives
Authors: Tarver Craig M.
Published: December 2004

The Pantex shock initation gap test, the Pantex corner turning test for detonation divergence, and recent short shock pulse shock initiation experiments using embedded gauges on TATB‐based solid high explosives are calculated in the two‐dimensional hydrodynamic computer code DYNA2D using the published ignition and growth reactive flow model for LX‐17. The calculations demonstrate that the Pantex gap test, like all gap tests for shock initiation, produces a complex two‐dimensional flow field involving a curved leading shock front and rarefaction waves form the rear and from the edge of the explosive being tested. The predicted brass gap thickness of 2.375 ± 0.125 mm for LX‐17 agrees closely with the measured critical gap thickness of 2.23 mm for 50% detonation. Excellent calculational agreement is also obtained with measured rates of detonation wave divergence for LX‐17 in the Pantex corner turning test. The reaction rates for TATB‐based explosives are varied to demonstrate the extreme sensitivity of this test to changes in explosive properties. Recent embedded particle velocity gauge experiments using various thickness flying plates of magnesium impacting PBX‐9502 are accurately calculated using the standard LX‐17 reaction rates.
Similarities of Shock Wave Damage in Air and in Water
Authors: Held Manfred
Published: December 2004

The damage done to structures in air or under water by a charge of mass W exploding a certain distance R away, can in both media be described by the so‐called square root relation, \documentclass{article}\pagestyle{empty}\begin{document}${\rm R} \approx \sqrt {\rm W}$\end{document}. This is better than a simple rule‐of‐thumb, because it implies the physical quantity of an energy density. It is shown that this energy density can also be derived from the product of peak overpressure times impulse for a blast wave in air or a shock wave in water.
The role of water in detonation of aluminium sensitized slurry explosives
Authors: Maranda A.
Published: December 2004

Results are given of measurements of the critical diameter of highly distributed aluminium sensitized slurry explosives. The role of water in the detonation process of the studied explosive mixtures is analysed on the basis of these results.
The glass transition temprature measurement of nitrocellulose by torsional braid analysis
Authors: Zhanning Jia
Published: December 2004

The glass transition temperature of pure nitrocellulose is determined by torsional braid analysis. The reproducibility and reliability of the measured results are discussed.
Do Not Convert Emulsions into Dynamites
Authors: Ekman Gunnar
Published: December 2004

The emulsion explosives have many advantages compared to dynamites from the safety point of view. However, there is a tendency to develop cartridged emulsions to be more and more dynamite‐like. According to our opinion this are steps in the wrong direction. It must be better to develop blasting methods, that are adjusted to the properties of the emulsions.
Fragmentation of Cast Iron Blocks by a Confined Explosive Charge: A new performance evaluation test for commercial explosives
Authors: Rao P. S. , Mohan V. Krishna , Bhasu V. C. Jyothi , Kumar A. S.
Published: December 2004

This paper describes a new method to assess the performance of small diameter explosives under laboratory conditions. While conventional strength tests often do not correctly reflect the performance characteristics of such explosives, model tests using rocks are not convenient due to constraints imposed by the size of the test block. Cast iron being a brittle material, fractures like rock and also its mechanical properties make it a suitable material for simulating rock under laboratory conditions. Tests have been carried out with different explosives in a cylindrical block of cast iron having a 27‐mm diameter central hole of a certain depth. Mean fragment size (X50) has been used as the criterion to rank different explosives with respect to their strength. Using fracture surface energy of cast iron and detonation properties of the explosives tested, the maximum fragment size could be predicted on the basis of an energy balance model. The predicted maximum fragment sizes are in fair agreement with the experimentally obtained ones. While the limitations of the proposed test are pointed out, it appears that cast iron block fragmentation could serve as an useful technique for evaluating the strength of commercial explosives.
Burning Rate Augmentation of BAMO Based Propellants
Authors: Oyumi Yoshio , Inokami Kiyotaka , Yamazaki Kazuhiro , Matsumoto Koki
Published: December 2004

Thermal decomposition and the burning properties of BAMO based propellants with HMX or AN/HMX have been investigated. The heat generated by the azide binder decomposition initiated and accelerated the thermal decomposition of HMX and AN. Ammonium perchlorate (AP) and lead stearate with carbon black significantly altered the mechanisms of the thermal decomposition and the burning properties of the HMX based propellants. AP showed an increase in burning rate with a slight decrease in burning rate pressure exponent. The lead catalyst yielded high value of the burning rate with the lowest pressure exponent. The ammonium dichromate also influenced the mechanisms of the thermal decomposition and the burning properties of the AN/HMX samples. The combination of ammonium dichromate and copper chromite was the most effective on the burning rate augmentation of AN/HMX based propellants. AN sublimed and evaporated from the condensed phase and mainly reacted exothermically in the gas phase HMX and AN/HMX based propellants showed smokeless burning characteristics in the small rocket motor combustion tests.
Characterization of plastic‐bonded explosives by pyrolysis gas chromatography and multivariate data analysis. Part I: Setup of the method
Authors: Rietjens M. , Wils E. R. J.
Published: December 2004

A further development of the procedure based on pyrolysis gas chromatography (Py‐GC) for the characterization of plastic‐bonded explosives (PBX's) is described. After grinding, the PBX samples were pressed on a pyrolysis wire followed by Py‐GC analysis. The peak areas obtained were normalized and subsequently submitted to multivariate data analysis. The use of principal component analysis (PCA) was tested on five samples which differed slightly in composition and age. The results were promising and showed that PCA is a powerful tool for the differentiation between PBX samples. The pyrolysis conditions were examined and optimized. A dependency was found between the sample loading (mass) and the position of the samples in a PCA score plot and indicates that control of the sample loading is important in obtaining reproducible results. For PBX samples an optimum pyrolysis temperature was determined around 540°C, close to the previous selected pyrolysis temperature of 610°C. In examining the pyrolysis at lower temperatures it was found that RDX or HMX is pyrolyzed independently from the binder. It appeared that PBX samples were inhomogeneous despite a thorough mixing of the constituents during preparation.
Thermomechanical Properties of Rocket Propellants and Correlation with cookoff behaviour
Authors: Ho S. Y.
Published: December 2004

The cookoff behaviour of several plasticized HTPB/AP and HTPB/RDX propellants has been evaluated using the standard Small‐Scale Cookoff Bomb (based on the NWC design) and a modified version of the standard equipment (whereby the reaction violence can be measured quantitatively) to investigate the effects of (1) plasticizer level on the thermomechanical properties and its role in moderating the cookoff response, and (2) heating rate. A change from slow to fast cookoff behaviour was observed for the plasticized HTPB/RDX propellants; the measured pressures/energy output at the slow heating rate were much lower than those at the fast heating rate for the same propellants. The thermal distribution/gradient at various positions and depths in the cylindrical propellant specimen, during fast and slow cookoff, were measured in order to understand the reversal in the severity of the response shown by the plasticized RDX propellants when the heating rate was changed. Thermomechanical properties of the propellants were measured and correlated with cookoff behaviour, to provide further insight into the cookoff mechanisms.
Effects of Copolymerization Ratio of BAMO/NMMO and catalyst on sensitivity and burning rate of HMX propellant
Authors: Kimura Eishu , Oyumi Yoshio
Published: December 2004

Three different copolymerization ratios of BAMO/NMMO copolymers were studied for the requirement of not only a high specific impulse but also an insensitive munition characteristics for HMX composite propellant. These molar ratios of BAMO/NMMO were 8/2, 7/3, 6/4. Although the heat of DSC measured was relatively largest in B/N(7/3) propellant, there was no difference in the thermal decomposition characteristics. The exothermic reactions of azide binder and of HMX occurred in the same temperature region. The faster burning rate was obtained by the more BAMO ratio in the binder. The shock sensitivity was the lowest in B/N(7/3) HMX composite propellant. This unexpected stability might be caused by the physical effect of the molecular structure of B/N(7/3) which might contribute to the sudden dumping of the impact shock. Although the detonation velocity, because faster as BAMO ratio, increased like as the burning rate, the detonation pressure was the lowest in B/N(7/3) propellant. The mixture of catocene and copper chromite augmented the burning rate 1.6 times with decreasing temperature sensitivity.
The Interaction between Otto Fuel II and Aqueous Hydroxylammonium Perchlorate (HAP), Part II: Gas Evolution and Changes in HAP Solution Acidity
Authors: Bellerby John M. , Blackman Christopher S.
Published: December 2004

Headspace gas analysis has shown that nitrous oxide (N2O) is the principal gas evolved during contact between small volumes of Otto Fuel II (OF) and 82% aqueous hydroxylammonium perchlorate (HAP) at temperatures close to ambient. The gas is produced mainly from the 82% HAP layer and is generated in significant amounts only after the OF has become blackened as a result of extreme degradation. The pH of the HAP solution falls during contact with OF and the OF blackening point is the same for each of three storage temperatures investigated, suggesting that the production of N2O may depend upon the attainment of a specific HAP solution acidity. It is suggested that the propyleneglycol dinitrate (PGDN) component in OF undergoes acid hydrolysis at the liquid/liquid interface and that the nitric acid produced leads to the decrease in HAP solution pH and to stabilizer depletion in OF. Experiments involving contact between 82% HAP and the other components of OF confirm the key role of PGDN: in its absence there is no change in HAP solution acidity, no gas evolution and no violent reaction between the two liquids.
Structural dynamics of nucleosome core particle: Comparison with nucleosomes containing histone variants
Authors: Ramaswamy Amutha , Bahar Ivet , Ioshikhes Ilya
Published: December 2004

The present study provides insights on the dominant mechanisms of motions of the nucleosome core particle and the changes in its functional dynamics in response to histone variants. Comparative analysis of the global dynamics of nucleosomes with native and variant H2A histones, using normal mode analysis revealed that the dynamics of the nucleosome is highly symmetric, and its interaction with the nucleosomal DNA plays a vital role in its regulation. The collective dynamics of nucleosomes are predicted to be dominated by two types of large‐scale motions: (1) a global stretching–compression of nucleosome along the dyad axis by which the nucleosome undergoes a breathing motion with a massive distortion of nucleosomal DNA, modulated by histone–DNA interactions; and (2) the flipping (or bending) of both the sides of the nucleosome in an out‐of‐plane fashion with respect to the dyad axis, originated by the highly dynamic N‐termini of H3 and (H2A.Z‐H2B) dimer in agreement with the experimentally observed perturbed dynamics of the particular N‐terminus under physiological conditions. In general, the nucleosomes with variant histones exhibit higher mobilities and weaker correlations between internal motions compared to the nucleosome containing ordinary histones. The differences are more pronounced at the L1 and L2 loops of the respective monomers H2B and H2A, and at the N‐termini of the monomers H3 and H4, all of which closely interact with the wrapping DNA. Proteins 2005. © 2004 Wiley‐Liss, Inc.
Synthesis of Functionalised Sulfonamides via Microwave Assisted Displacement of PFP‐Sulfonates with Amines
Authors: Caddick Stephen , Wilden Jonathan D. , Bush Hannah D. , Judd Duncan B.
Published: December 2004

A convenient microwave assisted synthesis of sulfonamides from PFP‐sulfonates is described. Reaction of various commercially available amines with pentafluorophenyl (PFP) sulfonate esters under microwave irradiation led to the corresponding sulfonamide products in good yields and without the requirement for chromatographic purification. The data shows that a number of functional groups are tolerated in both the amine and sulfonate ester and that the method can be extended to heterocyclic sulfonamides of potential biological interest.
Quantitative XPS analysis without reference samples
Authors: Ebel Maria F.
Published: December 2004

For approximately ten years there has existed a theoretically based concept of fundamental parameters for XRFA (quantitative X‐ray fluorescence analysis). From a comparison of the differences specific for XRFA and XPS it can be learned that this concept is also applicable to XPS and allows quantitative analysis without reference samples. Additionally, the influence of an overlayer on analytical XPS results is discussed. The theoretical considerations are confirmed by a series of measurements performed on binary and ternary alloys of Ag/Au/Cu and the results are compared with those of earlier measurements with reference samples. An averaged absolute accuracy of approximately ±2 wt% has been found for both methods, but the advantage of an absolute method needs no further comment.
A study of interface problems in polycrystalline GaAs Schotky barrier and MIS solar cells
Authors: Kazmerski L. L. , Ireland P. J.
Published: December 2004

AES, SIMS and XPS are used to investigate the interfaces in polycrystalline GaAs Schottky barrier and MIS solar cells. A significant interfacial chemical reaction is found to occur between Au and the GaAs in room temperature fabricated devices, with at least one phase, Ga2Au, identified using chemical peak shifts in XPS. Enhanced interdiffusion is reported at elevated temperatures for these structures. The primary mechanism is identified to be grain boundary diffusion, and the temperature dependence of the diffusion coefficient is estimated from the AES depth‐compositional data. The interface in the Ag/GaAs Schottky barrier is studied for comparison and is found to be stable to 573 K. The measured Schottky barrier heights and photovoltaic performances of these solar cells are correlated with the condition of the metal‐semiconductor interface. The advantage of including a thin oxide layer between the Au and GaAs (MIS structure) in preserving the integrity of the interfaces is demonstrated.
A sample introduction probe for XPS studies of air‐sensitive materials
Authors: Cudby M. E. A. , Charlton V. , Briggs D.
Published: December 2004

The design of a special probe for introducing air‐sensitive materials into a Kratos ES200B X‐ray photoelectron spectrometer is described and its performance discussed.
Quantitative measurement of impurities in GaAs layers by secondary ion mass spectrometry
Authors: Clegg J. B.
Published: December 2004

A quadrupole‐based SIMS system has been used for the localized impurity analysis of GaAs. Spectral interferences are reduced by using a mass filtered primary ion beam and UHV conditions in the target chamber with energy discrimination of the secondary ions. Practical detection limits for 12 elements have been determined with samples calibrated by other methods. Detection limits for important impurities in GaAs range from 1014 atoms cm−3 for Cr and Mn to 1016 atoms cm−3 for Si, Zn and Sn. Depth profiles are presented which demonstrate that this detection capability is attained with micron thick layers. Confirmatory evidence of profile shapes and impurity concentrations has been obtained from independent electrical data.
The development of surface shape during sputter‐depth profiling in Auger electron spectroscopy
Authors: Makh S. S. , Smith R. , Walls J. M.
Published: December 2004

Ion bombardment is an important process in surface analysis, not only for surface cleaning, but also for obtaining composition‐depth profiles through thin films and interfaces. Although the use of depth profiling is well established for initially flat surfaces and the problems associated with ion‐induced artefacts such as surface topography, preferential sputtering and redeposition are well recognized, the additional problems which occur when non‐flat surfaces are bombarded have been neglected. For example, depth profile analysis of rods, wires, fibres, etc., using Auger electron spectroscopy is now of interest for many commercial purposes. However, the erosion of such geometries is non‐uniform since different angles of incidence are presented to the incoming ion beam. In this paper, computer simulations are presented which illustrate the erosion of such geometries and a quantitative analysis is given for the resulting degradation in depth resolution as a function of sample and electron beam diameter.
A correlation of the average sample mass and the sputtering yield in SIMS
Authors: Katz William , Williams Peter , Evans C. A.
Published: December 2004

Previous work has shown that the sputtering yield of a matrix strongly affects the secondary ion yield of a material bombarded by reactive primary ions. Examining several homologous series of compounds, we have determined a linear correlation between sputtering yield and average substrate mass. This relationship enables quantitative predictions of the substrate sputtering yield and stoichiometry prior to SIMS analysis. This approach should be generally applicable to any sputtering technique.
Electron energy loss studies of the valence band density of states of scandium
Authors: Tougaard S. , Ignatiev A.
Published: December 2004

Electron energy loss spectroscopy of the scandium (0001) surface has indicated both core level and valence band excitation loss structure. Comparison to theoretically calculated bulk densities of states for scandium shows good agreement with the experimental results.
Surface structural investigations by photoemission spectroscopy
Authors: Margaritondo G.
Published: December 2004

Photoemission techniques are currently being used by several authors for surface geometry investigations. In particular great emphasis is being placed on photoelectron diffraction effects in the final state which are a direct source of structural information. Other surface structure investigations involve more conventional initial‐state photoemission experiments. We briefly discuss some of the above appraches and their advantages with respect to the ‘traditional’ structural probes.
Defect structures at solid surfaces
Authors: Lagally M. G. , Welkie D. G.
Published: December 2004

The analysis of surface structural defects at the atomic level using low energy electron diffraction (LEED) is briefly considered. The angular distribution of the diffracted intensity contains information on the defect structure. A number of defects can be distinguished and quantified by studying the behavior of the angular width of diffracted beams with changes in diffraction parameters.
ESCA studies of Ni‐25 At% Fe alloy. 1—surface preparation treatments and oxidation
Authors: Olefjord I. , Marcus P.
Published: December 2004

The surface compositions of Ni‐25 at% Fe single crystals ((100) and (110)) were analysed by ESCA. The spectra were interpreted by comparison with reference spectra obtained from Ni, Fe, NiO, Fe2O3 prepared in situ. Various surface pretreatments were investigated. The appropriate treatment to obtain a surface composition identical to the matrix composition is electropolishing and subsequent ion etching; the etching time is critical because the electropolished surface is enriched with nickel. Annealing at 800 °C can also be used to obtain the correct surface composition, but ion etching is then required to remove sulphur segregated to the surface during annealing. Oxidation at 25 °C and 500 °C (PO2 = 10−4Torr) gives an iron enriched oxide. At 500 °C, nucleation and lateral growth of oxide islands were observed. Both the islands formed in the early stage and the final oxide covering the whole surface have the composition of the spinel NiFe2O4.
ESCA studies of metals and alloys: Oxidation, migration and dealloying of cu‐based system
Authors: Barr Tery L.
Published: December 2004

A short, critical review is provided on the utilization of surface techniques, particularly ESCA, for the study of metal and alloy corrosion problems. Some of the attributes and difficulties of these techniques are considered. An interrelated series of Cu systems are chosen as representative examples of the use of ESCA in this type of study. Included are: (1) the oxidation in air (natural passivation) of polycrystalline Cu, (2) the thermal degradation of a Cu98Be2 alloy. This process readily exhibits preferential surface migration. (3) An ESCA study of the air oxidation of α‐brass (Cu75Zn25). This produces a clear example of preferential oxidation. (4) The ESCA analysis of this same air passivated α‐brass following progressive exposures to simulated seawater. This provides a dramatic example of ion‐field induced dealloying; i.e., dezincification.
Low energy electron loss studies of cuInSe2 surfaces
Authors: Jamjoum O. , Kazmerski L. L. , Lichtman D. L. , Bachmann K. J.
Published: December 2004

The low energy loss spectra (LELS) of clean and oxygen contaminated (111) p‐type CuInSe 2 single crystals are reported. Losses due to interband transitions and plasmon excitations are observed. By varying the primary electron energy (100–500 eV) both surface and bulk features of the conduction bands are probed. As oxygen is adsorbed on the surface of the CuInSe 2 (at room temperature), the In and Se atoms seem to associate with themselves and with oxygen, whereas the Cu atoms do not seem to play a direct role in the oxidation process. LELS Spectra are presented as a function of primary beam energy and oxygen absorption.
Surface structure and NiO dispersion for NiO/γ‐Al2O3 catalysts
Authors: Gambaro L. A. , Fierro J. L. G. , Tejuca L. González , Agudo A. López
Published: December 2004

Chemisorption of CO at temperatures below 100°C has been used to evaluate the dispersion of NiO in a series of NiO/γ‐Al2O3 catalysts. CO adsorption measurements were supplemented by i.r. spectroscopy to establish the CO/NiO stoichiometry. From monolayer coverage data derived from Freundlich's equation, the percentage of NiO dispersion and the average NiO crystallite size were calculated. The crystallite size of supported NiO was found to be practically constant for NiO loadings from 1 to 8 wt%, experimenting an abrupt increase for higher NiO contents. These results were consistent with additional information on the surface structure of the catalysts obtained by IR spectroscopy, X‐ray diffraction, magnetic susceptibility, and reduction with H2.
Transmission electron microscopy of ultramicrotomed barrier anodic films on aluminium
Authors: McCune R. C. , Plummer H. K.
Published: December 2004

Ultramicrotomy was utilized to produce thin section specimens of anodized aluminium to permit a measurement of the film thickness in cross section by transmission electron microscopy. This direct approach to film thickness measurement has an inherent precision of ±0.5 nm, and may be utilized to measure films as thin as 5.0 nm. Two types of film growth procedures were studied using this technique: one utilizing an aqueous ammonium tartrate solution as the electrolyte, and a second using a nonaqueous electrolyte of ammonium pentaborate in ethylene glycol. While both electrolytes yielded barrier values of approximately 1.5 nm V−1, in agreement with literature values, the aqueous electrolyte tended to show a zero‐potential offset of nearly 10 nm greater than the nonaqueous electrolyte. Furthermore, films grown in aqueous solutions tended to have a less dense surface morphology, which was distinguishable in transmission electron microscopy.
Analysis of diffusion mechanisms in thin polycrystalline Au–Ag films using auger electron spectroscopy
Authors: Bukaluk Antoni
Published: December 2004

The diffusion process of silver through gold polycrystalline films 1000 Å thick for different heating times and different temperatures was studied. Auger electron spectroscopy (AES) with simultaneous argon ion sputtering was used to obtain the composition profiles of silver diffusing through gold thin films. The interdiffusion coefficients were extracted from the diffusion profiles using the rate of decrease of the concentration gradient at the Au–Ag film interface (the ‘centre gradient’ method) and the rate of rise of Ag concentration plateau in the Au film (the ‘plateau rise’ method). The grain boundary diffusion coefficients have been evaluated by means of the depth profile analysis, based on the Whipple model. The activation energies of each mechanism have been determined from the Arrhenius plots.
X‐ray photoelectron diffraction studies of zinc selenide
Authors: Sian Crawford E. , Evans Stephen , Raftery Elizabeth , Scott Michael D.
Published: December 2004

Polar and azimuthal angle‐resolved XPS studies of ZnSe layers grown epitaxially on {100} GaAs by H2 transport of the elements are described. Comparison of the polar X‐ray photoelectron diffraction (XPD) patterns obtained for rotation about [110] and [110] axes confirms the dominant influence of structural factors in determining the shape of the patterns. Azimuthal XPD patterns are shown to reflect symmetry properties directly related to the emitting sites, and their use to determine the symmetry of an exposed single‐crystal surface is demonstrated. The outermost ∼100 Å of all the ‘as‐grown’ ZnSe layers were ∼20–35% Zn rich. Ar ion bombardment (800 eV, ∼5 μA) rapidly restored the surface stoichiometry to within 10% of 1:1. The disorder concurrently introduced resulted in XPS peak broadening without impairment of the polar XPD pattern. Annealing at 300°C in high vacuum removed the disorder without affecting either the stoichiometry or the XPD pattern. It is inferred that split‐<100> interstitials are the preferred sites both for atoms displaced by ion bombardment and for the excess Zn initially present.
SIMS study of the SiO2/Si interface and of the Si+O2 system
Authors: Degreve F. , Ged Ph.
Published: December 2004

Depth profiles of mono and polyatomic ions (Si+, SiO+, Si, Si++) have been determined by SIMS under Ar+ ion bombardment on 100 Å to 700 Å thick thermal SiO2 layers. The main experimental results are: (1) The best depth resolution is obtained with Si+ (49 ± 6 Å); (2) The ion intensity profiles plotted against the sputtering time are systematically shifted from one species to another; (3) The sputtering time needed to obtain a 50% signal variation in the interface region varies linearly with the oxide thickness for all the above species; (4) The slope of the corresponding straight lines are identical but the intercepts differ from 1 ± 6 Å for Si up to 36 ± 6 Å for SiO+. Furthermore, similar intensity shifts are seen for the above ions when a silicon substrate is argon bombarded under various oxygen pressure conditions. The experimental data shows that the shifts of the secondary ion profiles and the non zero intercepts are not necessarily due to cascade mixing and may involve sputter yield or ionization probability variations in the interfacial region.
GaAs oxides formed at room temperature in air: Comparison of X‐ray photoelectron spectroscopic and ion microprobe mass analyses
Authors: Demanet C. M. , Rawsthorne E. D. , Stander C. M.
Published: December 2004

An ion microprobe mass analysis (IMMA) study of the oxides formed on GaAs at ambient temperature and in ambient atmosphere is compared with a similar study carried out using XPS. The distribution of the various oxides identified from their unequivocal fragment ions is analysed. The multilayer model proposed on the basis of XPS results is largely confirmed with the exception of gallium hydroxide which, from the IMMA results, appears to be distributed across the whole oxide thickness.
Correlation between CdS photoanodic behaviour and electrode chemical modifications: An X‐ray photoelectron spectroscopic study
Authors: Riga J. , Verbist J. J. , Josseaux P. , Kirsch‐de Mesmaeker A.
Published: December 2004

The photosensitivity increase of CdS films as a function of the illumination time, is correlated to chemical changes of the electrode surface, analysed by XPS. It is shown that the formation of Cd(OH)2 or CdO is responsible for the photosensitivity change of the illuminated electrode in contact with H2O/NaOH alone. When thiocresol or p‐mercaptobenzoic acid is added as reductant, a layer of organic compounds is formed on the electrode during the photoelectrochemical process. However, the XPS and photocurrent spectra indicate that this layer does not prevent the occurrence of Cd(OH)2 or CdO responsible for the photosensitivity changes of the CdS film.
The shape of the background in AES: Nonlinear features in log N(E) v. Log E
Authors: Peacock D. C. , Duraud J. P.
Published: December 2004

By replotting emitted electron spectra, N(E), as log N(E) v. log E, parts of the background which obey a power law can be identified as linear segments. The importance of this linearity for Auger electron spectroscopy (AES), and the conditions under which it can be observed, are discussed. A simple expression is presented which describes the essential shape of the spectral background for analysis energies in the range 50–2000 eV and primary energies between 3 and 20 keV. It has been suggested elsewhere that such simple expressions are inadequate because ionization of inner shells by backscattered and secondary electrons can introduce broad low intensity features which disrupt the linearity of log N(E) v. log E. In the present work numerically calculated spectral shapes are compared with experimental AES spectra from various specimens including Al and Si. It is shown that some broad features which are often observed in EN(E) (constant spectrometer resolving power) spectra arise solely as a consequence of replotting power law backgrounds in this form and cannot be adduced as evidence of the ionization mechanism. Furthermore, subsurface electron sources can cause nonlinearities in logarithmic spectra which should not be ascribed to the ionization mechanism. It is concluded from a comparison of calculated spectra with those observed experimentally that the ionization mechanism causes only small deviations from linear behaviour which should not prevent the fitting of power law backgrounds to experimental AES data.
Quantifying data from Auger spectra and images
Authors: Walker C. G. H. , Peacock D. C. , Prutton M. , El Gomati M. M.
Published: December 2004

A method for quantifying Auger spectra and including matrix effects is described. This method corrects iteratively for the effects of electron back‐scattering, the inelastic mean free path and atomic density in the sample using established methods. New algorithms have been developed to assist the user interactively with the analysis of spectra collected from surfaces covered by thin films of unknown composition or thickness, or by coverage of another material. Error analysis has been included for both homogeneous and thin film cases. A ‘figure of merit’, used to inform the user if a thin film model of the surface is accurate, is introduced. The algorithms can be implemented on a small microcomputer. Their application to quantitative Auger analysis by multi‐spectral imaging is also described. Each point in a set of images has been corrected for the factors that influence the Auger current to arrive at surface compositions at each pixel for each element. Some of the advantages and problems of quantifying Auger images will be outlined. The use of multi‐spectral Auger images is seen as a powerful means of identifying surface phases of materials and is given the acronym MULSAM—MULti‐Spectral‐Auger Mapping.
Effect of analytical method on thickness measurements of thin oxide films
Authors: Tapping R. L. , Davidson R. D. , Jackman T. E. , Davies J. A.
Published: December 2004

The thickness of thin natural oxide films formed on silicon, nickel, aluminium, iron, tantalum and zirconium has been measured using nuclear reaction analysis (NRA) and Auger electron spectroscopy (AES) in combination with ion beam sputtering. It is shown that ion beam effects severely limit the use of AES and ion beam sputtering in measuring thin oxide thicknesses. Relatively non‐destructive techniques such as NRA or angle‐resolved x‐ray photoelectron spectroscopy (XPS) provide more reliable information.
Esca and reels characterization of electrically conductive polyimide obtained by ion bombardment in the keV range
Authors: Marletta Giovanni , Oliveri Carmelo , Ferla Giuseppe , Pignataro Salvatore
Published: December 2004

Polymide films were bombarded with Ar+ at 150 keV at various doses from 5 × 1012 to 2 × 1017 ions cm−2. Ion bombardment was found to produce a drastic decrease of the electrical resistivity of the polymide from about 1016 to 3 × 10−3 Ω cm, the effect being dependent on the ion dose. The chemical structure of the conductive films obtained was characterized by means of ESCA and REELS techniques. The modification of the original polymer seems to proceed at low ion doses (up to 5 × 1014 ions cm−2) by means of the progressive elimination of the carbonyl groups and the related destruction of the imidic rings, while at high doses (from 5 × 1015 ions cm−2) the carbonization of the polyimide occurs with the production of an amorphous carbon still containing significant amount of residual N and O atoms.
X‐ray photoelectron spectroscopy and surface charge build‐up used to study residue on aluminum contacts on integrated circuits
Authors: Thomas J. H. , Bryson C. E. , Pampalone T. R.
Published: December 2004

X‐ray photoemission induced surface charge build‐up with a charge control screen and small spot analysis was used to study processing residue layers deposited on aluminum–silicon metallization as found in high aspect ratio via regions on silicon integrated circuits. Chemically vapor deposited silicon dioxide on Al: 1% Si metallization is commonly found in double level metallization of intergrated circuits. An interdigitated fine‐line test pattern with lines ranging from 500 nm to 2000 nm and variable spacing was used to simulate a typical integrated circuit structure. X‐ray photoemission studies of processed test circuits have led to the following conclusions. Line patterns CHF3 plasma etched into 800 nm SiO2 to expose Al were found to be contaminated with a dominant carbide and a minor oxyfluoride compound. Both Al carbides and Al oxyfluorides are non‐volatile compounds and hence are not readily removed during plasma etching or ashing. This surface layer is deposited by a combination of fluorine in the plasma interacting with the aluminum surface, side wall deposition of carbon from the photoresist, and ion induced mixing of the surface region. Deposits found on similarly processed planar structures were contaminated with Al oxyfluoride and no detectable amount of carbide. Back‐scattered Al(OF)x was observed on the SiO2 surface due to the plasma ashing photoresist removal step.
A Raman spectrophotometric investigation of the phases formed during the cobalt silicidation by rapid thermal anneal
Authors: Shergill Gurmeet S. , Wei Chih‐Shih , Cox J. Neal , Fraser Dave B. , Murray Jeff J.
Published: December 2004

Raman spectrophotometry was used to determine the various phases of cobalt silicide formed during rapid thermal annealing of cobalt films deposited onto silicon (100) substrates. The samples were prepared by depositing a 600 ÅR cobalt film and then letting the reaction occur in a nitrogen ambient. Annealing was done for 20 s at temperatures ranging from 200 to 1000°C. The unreacted cobalt film was removed from the surface for the Raman spectrophotometric study. The initial phase, characterized as Co2Si, formed at 250°C. Two subsequent phases, CoSi and CoSi2, were identified as forming at 300 and 500°C, respectively. The corresponding three Raman peaks appeared at 204, 306 and 515.3 Δcm−1, respectively. These peaks appeared and disappeared in accordance with the phase change in the film. The co‐existence of the two initial phases, Co2Si and CoSi, at temperatures near 300°C was also evidenced by Raman spectrophtometry. The Raman data correlated well with Auger electron spectroscopic depth profiles.
SIMS analysis of GaP–GaAsP layered structures
Authors: Söudervall U. , Leys M. R. , Lodding A. , Samuelson L.
Published: December 2004

The paper describes the characterization by SIMS of thin layers of GaAsxP1 − x between layers of GaP. The investigation aims at quantification of the arsenic concentration, x, in layers with thickness ranging from 20 to 100 nm.

The study reveals a nearly constant sensitivity factor in the SIMS quantification of the arsenic content of the GaAsxP1 − x layers. The sensitivity factor was found to be 4.3 × 10−3 over the range x = 0.10–0.75, with no distinct concentration dependence.

Depth resolution and decay length λ(0) were measured by analysing the interfaces of the GaAsxP1 − x structures at different primary ion energies (1.5–13 keV). The best depth resolution, 3.2 nm, is obtained at 1.5 keV and the worst, 13 nm, at 13 keV. Decay length evaluations are consistent with a collisional mixing theory for the sputter‐induced broadening of an interface.
Factor analysis of d(NE)/dE Auger electron spectra of AuCu alloys: Surface composition during Ar+ ion bombardment and oxidation
Authors: Jansson C. , Morgen P.
Published: December 2004

Factor analysis is applied to d(NE)/dE Auger electron spectra of a series of AuCu alloys (25% Au, 50% Au and 75% Au), including in the analysis the spectra of clean Au and Cu surfaces. Surface quantitation is obtained from the low‐energy Au NOO and Cu LMM spectra of the alloys. The overlap of these spectra is resolved with factor analysis. An accuracy of the derived, relative surface concentrations of 1:100 is possible with this method, with a similar sensitivity to changes in surface composition. During Ar+ ion bombardment the surfaces of 25% and 50% Au alloys show no difference from the bulk concentrations, within ±1:100, from 1 to 3 keV Ar+ ion energy. For the 75% Au alloy, a slight Au enrichment is produced, when the energy increases from 1 to 3 keV. However, at 500 eV Ar+ ion energy, the surfaces become strongly enriched in Au, probably due to threshold effects for Au. Thus, no evidence for such strongly varying processes are found in molecular dynamics simulations of the mass effect in the sputtering process from a 50%:50% alloy. Factor analysis is also used to detect the presence of chemically affected spectral features during oxygen exposure at room temperature of the alloys and of pure Cu. Oxidation of the copper component is observed, producing at saturation a cuprous oxide with a total copper enrichment of the surface.
Secondary effects in laser ionization surface analysis
Authors: Rohr K. , Thoemmes R.
Published: December 2004

Contaminated tantalum surfaces have been analysed by a modified laser ionization mass analysis (LIMA) technique in order to investigate the reliability of this method in a situation where the ion yield is optimum. The laser was an Nd‐YAG Q‐switch system (λ = 1.06 μm) of τ = 20 ns pulse length delivering an energy of 0.3 J in the TEM00 mode. Ions desorbed from the surface and the substrate have been analysed according to their mass and charge and their kinetic energy distribution. The results strongly suggest that the effective region of the surface desorption can be one order of magnitude larger than the geometrical focal region of the laser beam where the substrate particles are desorbed. The effect is explained by secondary Bremsstrahlung interaction. Generally, this imposes severe restrictions on the reliability of quantitative spatially resolved surface analysis techniques where laser‐induced high‐temperature plasmas are present.
Analysis of superconducting thin films by ion beam methods. Comparison of nuclear techniques and SIMS
Authors: Stoquert J. P. , Fogarassy E. , Stuck R. , Guillaume G. , Siffert P. , Perrière J.
Published: December 2004

Thin layers of YBaCuO and BiSrCaCuO superconducting oxides have been deposited on different substrates by the laser evaporation technique using a pulsed ArF excimer laser. The films were analysed by different ion beam techniques: nuclear reaction (NR), particle‐induced x‐ray emission (PIXE), Rutherford back‐scattering (RBS), elastic recoil detection (ERD) with high‐energy incident ions, and secondary ion mass spectroscopy (SIMS). Conventional PIXE and RBS with proton and helium beams were used to determine the mean stoichiometry and the near‐surface composition for the heavy elements of the target, and the 16O(d, α)14N nuclear reaction was employed at Ed = 900 keV (θd = 150°) to profile the oxygen content in the layers. In order to obtain detailed information on the variations of the relative concentration in depth, SIMS was also performed on thin layers and on bulk superconducting target prepared by standard ceramic techniques. Absolute profiles of matrix elements, from O to Bi, were also determined by the ERD technique using high‐energy (up to 240 MeV) heavy incident ions (127I) and a ΔE–E gas telescope in order to discriminate between the recoiling atoms.

Finally, the resolution and sensitivity of the different methods are compared.
Secondary ion shadow‐cone enhanced desorption
Authors: Chang Che‐Chen
Published: December 2004

The incident angle dependence of the secondary particle emission process under keV ion bombardment has been investigated. The results from the full molecular dynamics calculations indicate that the flux anisotropy of the incident beam, resulting from the non‐uniform impact parameters for the surface atom of a single crystal, affects the particle desorption in a systematic fashion. The enhanced desorption at certain angles of incidence corresponds to the intensive focusing of the incident beam to the near‐surface atom and the extended dissipation of momentum by large‐angle scattering. This observatvon has led us to develop a new theoretical model in which the enhanced desorption is described by the distance of closest encounter along the trajectory of the incident particle to the surface atom. The computer time for the simulation of the incident‐angle‐dependent emission process is significantly reduced. The results from the calculation based on this model are in good agreement both with the results from the full dynamics calculation and with the experimental results. The new model also allows a complementary evaluation of the microscopic dynamics involved in the shadow‐cone enhanced desorption.