bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation of surface segregation in magnetron‐sputtered NbSi using UPS and AES
Authors: Hucknall P. K. , Walker C. G. H. , Greig D. , Matthew J. A. D. , Norman D. , Turton J. 
Published: December 2004

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

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

AbstractWhen energetic ions penetrate and stop in solids they not only add a new atomic constitutent to the matrix but they also create atomic recoils and defects. The fluxes of these entities can give rise to spatial redistribution of atomic components, which may be partly or completely balanced by reordering and relaxation processes. These latter, in turn, may be influenced by fields and gradients induced by the primary relocation processes and by the energy deposited. These will include quasi‐thermal, concentration (or chemical potential) and electrostatic gradients and may act to enhance or suppress atomic redistribution. Some, or all, of these processes will operate, depending upon the system under study, when energetic ions are employed to sputter erode a substrate for depth sectioning and, quite generally, can perturb the atomic depth profile that it is intended to evaluate. Theoretical and computational approaches to modelling such processes will be outlined and experimental examples shown which illustrate specific phenomena.In particular the accumulation of implant species and defect generation or redistribution can modify, with increasing ion fluence, the local sputtering mechanism and create further problems in depth profile analysis as a changing surface topography penetrates the solid. Examples of such topographic evolution and its influence on depth profiling analysis will be given and models to explain general and specific behaviour will be outlined. The commonality of models which examine both depth‐dependent composition modification and surface topography evolution will be stressed.
Estimation of the grain boundary coverage of segregated impurities from the kinetics of free surface segregation
Authors: Menyhard M. 
Published: December 2004

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

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

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

AbstractIn an NiFe/Ta system, interface widths (Δz) are compared for sputter profiles with stationary and rotating sample holder (Zalar rotation). For low sputter angles, the Zalar rotation brings considerable improvements in Δz. For higher sputter angles, the improvement available through Zalar rotation vanishes as self‐shadowing due to crystallites with less favorable orientation becomes the dominating rate mechanism. The improvement is further reduced for thinner films much below 1000 Å. For low sputter energies and films 125 Å thick, Zalar rotation has no influence. The limit of depth resolution was 30 Å, which resulted from the substrate‐induced roughness of the NiFe/Ta interface. The interface width's maximum near 30° for stationary sputter etching is characteristic of sputter‐deposited fcc films.
Quantitative AES depth profiling of thin oxide films grown on stainless steels and aluminium
Authors: Lorang G. , Xu J. L. , Langeron J.‐P. 
Published: December 2004

AbstractAES depth profiling was performed in passive overlayers grown on the surface of stainless steels and in alumina films formed on aluminium at 250°C in oxygen. Our quantitative approach is based on the sequential layer sputtering model proposed by Benninghoven and Hofmann for analysis of thin layers (<10 nm). A careful measurement of AES sensitivities in pure standards constituted by metallic elements (for the substrate) and their corresponding normal oxides (for the film) is needed to achieve the necessary conversion of AES sputter profiles into atomic concentration profiles. With the assumptions of (1) an oxide film and a metallic substrate assimilated to two distinct media separated by a step‐like interface and (2) a time‐invariant sputter rate, the method provides an available determination of the film thickness mainly dependent on an appropriate choice for attenuation lengths of Auger electrons. The usual approximations and results should therefore be discussed in the light of the determination of absolute oxygen film contents by means of nuclear reaction analysis (NRA).
Caesium‐ion‐induced Auger emission from aluminium and silicon
Authors: Maydell E. A. 
Published: December 2004

AbstractCs+‐induced Auger emission from aluminium and silicon is reported. The atomic‐like features in the spectra are identified and compared with data reported by others for bombardment with noble gas ions. Ion‐induced Auger spectra for aluminium and silicon, measured during the sputter‐etching of an aluminium‐on‐silicon structure, are used to generate dynamic Auger depth profiles for this structure. The ion‐induced Auger profile correlates with an AlCs+ secondary ion enhancement observed in the Cs+ ‐ ion dynamic SIMS depth profile, approaching the Al/Si interface. This AlCs+ enhancement parallels a SiCs+ secondary ion enhancement in the early stages of depth profiling of a fresh silicon surface with a Cs+ ion beam.
Prospects of x‐ray microscopy and x‐ray microtomography for interface studies
Authors: Erre D. , Thomas X. , Mouze D. , Patat J. M. , Trebbia P. , Cazaux J. 
Published: December 2004

AbstractMicrofocal x‐ray projection microscopy allows the non‐destructive investigation of thick specimens with a lateral resolution in the micrometre range. The minimum detectable thickness lies below 100 nm for strongly absorbing materials. For further investigation, x‐ray microtomography leads to three‐dimensional reconstruction of the specimen. Some applications of x‐ray microscopy are connected with the localization and imaging of solid/solid interfaces deeply buried in a matrix. In the future, solid/liquid interfaces and their motion will be of interest. The performance of x‐ray microscopy is discussed and x‐ray projection images obtained with a simple modified scanning electron microscope are shown.
A comparative study of the influence of surface pretreatment on the failure characteristics of adhesively bonded titanium
Authors: Watts J. F. , Dempster B. R. 
Published: December 2004

AbstractThe durability of adhesive joints fabricated from two titanium alloys, commercially pure titanium (TA6) and Ti–6Al–4V (TA10), has been investigated using the wedge cleavage test. Seven different methods of adherend pretreatment were investigated: writ blasting (GB), chromatic acid anodizing (CAA) and sodium hydroxide anodizing (SHA), used alone and with the addiiton of an epoxy primer prior to adhesive bonding. A silane adhesion promoter was also used in conjunction with the grit‐blasted adherend. As expected, the durability depended critically on the substrate pretreatment, with SHA‐treated joints giving the best durability and GB the worst performance. The application of a primer or adhesion promoter tended to improve the situation somewhat. The failure mode was apparently adhesive (interfacial), but when the interfacial failure surfaces were examined by XPS, polymeric residues were identified on the adherend surfaces of all joints. In the case of those joints that exhibited good durability three was evidence of transfer of titanium to the polymer side of the locus of failure. The locus of failure in these cases may be described in terms of a mixed mode failure on a microscale.
Thermal stability and degradation mechanisms of trialkylsilyl surface modifications on silica powder
Authors: Severin J. W. , Van Der Wel H. , Camps I. G. J. , Baken J. M. E. , Vankan J. M. J. 
Published: December 2004

AbstractThe thermal stability of a number of trialkylsilyl surface modifications has been studied. During heating, weight loss is recorded by thermogravimetry, while evolved gases are simultaneously analysed with mass spectrometry. Changes in the molecular structure on the surface are measured with solid state nuclear magnetic resonance (NMR) and static‐SIMS. Degradation mechanisms are proposed and described by a number of reaction equations. The changes in surface chemistry on the internal powder surface as measured with NMR are similar to those observed with static‐SIMS on the outer surface of the powder particles.
Quantitative studies of the initial oxidation stages of FeCrNi alloys using factor analysis and least‐squares fitting methods applied to low‐energy AES spectra
Authors: Steffen H. J. , Hofmann S. 
Published: December 2004

AbstractThe oxidation behaviour of the alloys Fe–19 at.% Cr–9 at.% Ni and Ni–40 at.% Fe–20 at.% Cr was studied in situ at room temperature and oxygen pressures below 10−4 Pa by AES using low‐energy M23VV transitions between 20 and 70 eV. Quantitative determination ofthe relevant components by factor analysis and least‐squares fitting methods enabled a much more detailed analysis of the initial oxidation stages as compared to earlier studies. For all alloy elements, factor analysis revealed the presence of an intermediate chemical state before oxidation which is due to binding with chemisorbed oxygen. Least‐squares fitting with standrd spectra of the pure elements in their metallic, oxidic and intermediate states disclosed the sequential oxidation of Cr, Fe and Ni with increasing oxygen exposure. Preferential oxygen chemisorption on Cr and oxidation of Cr is accompanied by oxygen‐induced segregation and is followed by Fe and Ni oxidation on top of the previously formed oxide for the Ni‐rich alloy. Nickel oxidation is drastically reduced in Fe‐rich alloys. After exposure to 900 L of oxygen, oxidation results in a layered structure as confirmed by AES sputter depth profiles which can be resolved into oxide and pure metal components. Together with the small electron escape depth of only 2–4 atomic layers, this procedure gives well‐resolved depth distributions within the total oxide thickness of ∼6–7 monolayers for NiFe40Cr20 and 11–12 monolayers for FeCr19Ni9.
Methods of electron spectra processing based on solving the transport equation of electron motion in a solid
Authors: Borodyansky S. 
Published: December 2004

AbstractWithin the transport approximation, the problem of the elastic and inelastic scattering of Auger electrons, photoelectrons and backscattered electrons is investigated. The use of an invariant‐embedding approach allows the derivation of analytical expressions for the path length distribution for both emitted and backscattered electrons. These functions are used to produce a new procedure for background subtraction in AES/XPS and to develop a technique of REELS processing to reconstruct both the electron differential energy loss cross‐section in a solid and the ratio λi/λtr, where λi is the inelastic mean free path and λtr is the transport path for elastic scattering.
Reference samples for depth profiling: Highly accurate calibration of implanted ion dose by neutron activation analysis
Authors: Garten R. P. H. , Bubert H. , Palmetshofer L. 
Published: December 2004

AbstractTo prepare a candidate reference material for depth‐profiling analysis by AES, XPS, SIMS, SNMS, ISS, RBS, etc., silicon wafers were implanted with cobalt ions at an energy Eo = 300 keV. The total implanted doses, 1012 <D <1017 Co ions cm−2, were determined by instrumental neutron activation analysis (INAA) within a dynamic range of five decades. A high accuracy of better than 1.5% was attained. This is considered to be adequate for reference materials dedicated to depth‐profiling analysis by AES, XPS, SIMS, SNMS, ISS and RBS. INAA can offer the determination of 14 prominent elements, to be implanted in high‐purity materials, with limits of detection DLD <109 ions cm−2.
Validity of background correction algorithms studied by comparison with theory of synchrotron‐radiation‐excited core levels and their corresponding auger peak intensities
Authors: Jansson C. , Hansen H. S. , Jung C. , Braun W. , Tougaard S. 
Published: December 2004

AbstractThe validity of the Shirley, the straight line and the Tougaard methods for background correction of electron spectra is studied under variation of the photon energy by using a synchrotron light source. For C and Ag the intensity ratio of the peak from a photon‐excited core level and the corresponding Auger transition is compared with theory. This ratio is independent of the possible error in photo‐ionization cross‐sections. The deviations are found to increase with increasing photon energy. Possible explanations are discussed in terms of errors in the elastic mean free path and energy dependence of the analyser response function as well as the characteristics of the monochromator. The agreement between theoretical and experimental ratios is better for the Shirley method than for the straight line method and significantly best for the Tougaard method.
Electromigration of metallic islands on Si(001) surface
Authors: Ichinokawa T. , Iizumi H. , Haginoya C. 
Published: December 2004

AbstractElectromigration of metallic islands formed by vapour deposition on the Si(001) 2 × 1 surface has been investigated by an ultrahigh vacuum scanning electron microscope (UHV‐SEM) at temperatures higher than the melting points of the islands with heating by passing dc current through the Si substrate. The direction of the island migration depends on the kind of metal. The speed is approximately proportional to the island radius and increases exponentially with temperature. The activation energy for migration of Au islands is 0.6 eV. The driving force of the island migration is discussed.
Development of a hyperthermal oxygen‐atom generator
Authors: Hoflund Gar B. , Davidson Mark R. , Outlaw R. A. 
Published: December 2004

AbstractA source that is compact, durable and mounts on a standard standard ultrahigh vacuum (UHV) flange has been developed for the generation of hyperthermal oxygen atoms. In this source oxygen atoms permeate through an Ag membrane held at 500°C and are then emitted toward the target from the vacuum side of the membrane by electron‐stimulated desorption. The current prototype model generates useable O‐atom fluxes of ∼1012 atoms cm−2 s−1, and future modifications should increase this flux by 1–3 orders of magnitude. Based on the O+ energy distribution, the average O neutral energy is ∼5 eV with a fairly broad distribution (full width at half‐maximum ∼3.6 eV). The information required for the development of this source and the design of the source are prsented.
Oxidation in preparation of oxide superconducting films by MBE using NO2 and O3 gases
Authors: Nonaka H. , Shimizu T. , Hosokawa S. , Ichimura S. , Arai K. 
Published: December 2004

AbstractIn order to prepare oxide superconducting films by molecular beam epitaxy (MBE), we developed a compact NO2 supersonic molecular beam source and a new ozone jet generator to supply oxidizing gases with high controllability. Using these sources, oxide superconducting films of REBa2Cu3Ox (RE  Nd, Y) were prepared on either MgO or SrTiO3 substrates. Because of the sufficiently low pressure during deposition, the oxidation process of the metals, especially of copper, by the oxidizing gases and the crystallization and surface flatness of the films were studied in situ by XPS and reflection high‐energy electron diffraction (RHEED) together with effective cleaning of the substrates by the oxidizing gases.
Characterization of AlGaAs/GaAs interfaces by EELS and high‐resolution Z‐contrast imaging in scanning transmission electron microscopy (STEM)
Authors: Lakner H. , Maywald M. , Balk L. J. , Kubalek E. 
Published: December 2004

AbstractRecent developments in scannning transmission electron microscopy (STEM) instrumentation have pushed the limits of the achievable spatial resolution for analytical measurements into the subnanometer regime, which is necessary for the characterization of semiconducting heterostructures and interfaces. Z‐Contrast (or high‐angle annular dark field) imaging combines atomic resolution with chemical contrast. Such images are not affected by contrast reversals due to objective lens defocus or changes in specimen thickness, such as phase contrast images (bright field images). Parallel detection of electron energy‐loss spectra allows spatially resolved quantitative chemical information to be obtained even for high energy losses and when using a very fine electron probe diameter (down to < 0.3 nm). Examples demonstrating the performance of these techniques are given for AlGaAs/GaAs heterostructures used for very high speed and very high frequency devices. While high‐resolution Z‐contrast imaging is superior with respect to the spatial resolution achieved and the acquisition time needed, electron energy‐loss spectroscopy (EELS) can be used to record chemical line profiles with slightly decreased spatial resolution. In particular it can be used to quantify the Z‐contrast images by means of point analysis. Thus, the combination of Z‐contrast imaging and EELS can give information beyond the scope of either individual characterization technique.
Characterization of chromatized hot‐dip‐galvanized steel and 55% AlZn‐coated steel using ESCA and AES
Authors: Nilsson J.‐O. , Hörnström S.‐E. , Hedlund E. , Klang H. , Uvdal K. 
Published: December 2004

AbstractChromating of metals has been used for a long time as corrosion protection. In this study two commercial products for chromating, one based on chromates (Iridite 9L‐6) and one with an addition of a polymer (Okem Coat F1), have been analysed on hot‐dip‐galvanized steel, 55% AlZn‐coated steel and pure Zn, Al and Au. The analysis techniques used for this study were electron spectroscopy for chemical analysis and scanning Auger microscopy. With these methods it has been possible to characterize binding energies of different compounds in chromating coatings and to record elemental maps and depth profiles. Coatings formed in the laboratory have been compared with those from production lines. Comparisons of Cr6+/Cr3+ ratios of the chromating coatings formed on different substrates revealed that Cr6+ in a thin coating on Zn is almost completely reduced to Cr3+, while on Al the reducton of Cr6+ is very limited. On hot‐dip‐galvanized steel the Cr6+/Cr3+ ratio is higher than on 55% AlZn‐coated steel. This can be explained by differences in chromate coating thicknesses on hot‐dip‐galvanized and 55% AlZn‐coated steel. The coating formed by Iridite 9L‐6 on 55% AlZn‐coated steel is preferentially found in the interdendritic areas. Okem Coat F1 forms a slightly more homogeneous chromium coating on 55% AlZn‐coated steel as compared to that of Iridite 9L‐6. On the basis of the aqueous chemistry of chromium compounds, models are discussed for the formation of the chromating coatings.