bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxidation of an NiTi alloy
Authors: Chan C.‐M. , Trigwell S. , Duerig T. 
Published: December 2004

AbstractIn this study, the oxidation of the surface of a 50/50 (at.%) NiTi alloy was studied by XPS, AES and SEM. Samples of the NiTi alloy were oxidized at 23°C and high temperatures at an oxygen pressure of 10−4 Torr and in atmosphere. At 10−4 Torr of O2 and 23°C, titanium was oxidized preferentially while nickel remained in the metallic form even after 40 min of exposure. At the same oxygen partial pressure and 400°C, a mixture of TiOx, Ti2O3 and TiO2 was formed, and nickel remained metallic. Eventually, after 40 min of O2 exposure, the whole surface was covered with a layer of TiO2. In atmosphere and at 23°C, titanium again was oxidized preferentially, but NiO was detected on the surface after the first minute of air exposure. At a higher temperature of 450°C, areas comprising a mixture of NiO and TiO2, and areas consisting of TiO2 only were found. Below the top surface layer, a complete layer of TiO2 was detected. Underneath the TiO2 layer, a nickel‐rich layer was present.
XPS study of the state of oxygen on a chemically treated glass surface
Authors: Mohai M. , Bertóti I. , Révész M. 
Published: December 2004

AbstractThe O 1s line of an ordinary, untreated glass surface and of a glass surface in its dealkalized state were studied by XPS. One single O 1s peak was detected on the dealkalized sample at a binding energy (BE) of 532.5 eV while on the alkali‐containing sample, and also on the dealkalized sample after alkali solution treatment, a second peak at 531.1 eV BE also could be detected. Experimental data were backed by semi‐empirical quantum chemical calculations. The observed low BE component of the O 1s line, according to the outlined experimental evidence, is connected with the presence of alkali ions. This clearly contradicts earlier publications, interpreting the O 1s line as originating from oxygen atoms in bridging and non‐bridging positions.
Influence of surface melting treatment by laser on the segregation of sulphur, nitrogen and chromium on the surface of a single‐crystal FeCrNi alloy
Authors: Moulin G. , Larere A. , Marcus P. 
Published: December 2004

AbstractAfter melting the (100) surface of a FeCrNi single crystal by a CWCO2 laser, a quasi‐epitaxial regrowth of the melted zone takes place2 within a misorientation of ∼4°. Three distinct areas are obtained: unaffected, heat affected and melted surfaces. On all areas, the segregation of sulphur alone occurs at high temperature, while there is a cosegregation of sulphur and nitrogen at T < 700°C. The thermodynamic interpretation of the segregation results is reported.For the surface segregation of sulphur, no interactions are noted with other alloy elements, except with chromium on the unaffected surface. The difference between the free enthalpies of segregation of sulphur on the untreated and treated surfaces is associated with the evolution of the defect content.When sulphur and nitrogen cosegregate on the surface of the untreated alloy, a repulsive coefficient of interaction between sulphur and nitrogen (i.e. βSN) of the order of 20 ± 5 kJ mol−1 is calculated. For the laser‐treated surfaces, the chromium content increases on the surface. Then, the regular solid solution model is applied to the CrNS ternary system. The calculated βSN coefficient is now 45 ± 5 kJ mol−1 and agrees with the experimental data obtained from the experimental evolution of ΔG versus YN (with ΔG = free energy of segregation of S and data YN = nitrogen concentration on the surface). More complex interactions are also discussed, especially for nitrogen, on account of the site competition between N and S and the influence of the vacancy content on the treated surfaces.
Optimization of the dynamic range of SIMS depth profiles by sample preparation
Authors: von Criegern R. , Weitzel L. , Zeininger H. , Lange‐Gieseler R. 
Published: December 2004

AbstractThe dynamic range is one of the most important figures of merit of SIMS measurements and equipment. The term refers to the concentration range of an analysed element—its concentration being high near the surface but decreasing with increasing depth—that can be measured by depth profiling. The state of the art is such that, under favourable conditions, 5–6 orders of magnitude are possible (measured on ion‐implanted boron in silicon). It is shown that with special sample preparation techniques (removal of the sputter crater environment) the dynamic range can be extended to 7 orders of magnitude. Experimental details of the preparative methods are given together with a critical evaluation of the methods.
An AES study of the room‐temperature oxidation of TaSix after bombardment with Ar+ ions of different energies
Authors: Clement M. , Sanz J. M. , Martínez‐Duart J. M. 
Published: December 2004

AbstractTantalum silicide films of ∼200 nm thick and composition TaSi2 were obtained by co‐sputtering in a Varian 3120 S‐gun magnetron system. The films were then introduced in an AES spectrometer and bombarded with Ar+ ions of different energies in order to obtain surfaces of different compositions as a consequence of preferential sputtering effects and their dependence on the energy of the primary ions. Lowering the energy of the Ar+ ions resulted in surfaces very rich in tantalum. The interactions of these surfaces with oxygen at low pressures (10−8−10−5 Torr) and at room temperature then have been studied comparatively by Auger electron spectroscopy. Reference experiments with pure Si and Ta allowed the comparison with those of the different silicide surfaces. It is found that the oxygen uptake depends on the Ta content so that the richer in Ta the surface is, the higher the O2 incorporation. Furthermore, the uptake rate at the different TaSix surfaces resembles better the measured rate for pure Ta than that observed for pure Si. It has been observed also that the oxidation of Si is enhanced over that of pure silicon in all the surfaces studied here. Besides, the enhancement depends on the tantalum content.
Determination of the sputtering rate of electroless nickel layers with a glow discharge lamp
Authors: Böhmer R. G. , Nel J. T. 
Published: December 2004

AbstractGrimm glow discharge spectrometry was used to analyse electroless nickel coatings on a steel substrate. Because of poor depth resolution at the coating/metal interface, it was necessary to determine the sputtering rate of the layer itself at different power settings and to calculate the sputtering rate per power unit. The penetration time for layers with different thicknesses was also determined for different power settings. By comparing sputtering rates per power unit, it was found that the best results were obtained if the penetration time was equated to the time needed for the nickel signal to reduce to half its original value.
Surface characterization of chemically modified chrysotile asbestos by particle‐induced desorption mass spectrometry
Authors: Bennett J. A. , Schweikert E. A. , Poisson D. , Jolicoeur C. 
Published: December 2004

Abstract252‐Cf particle‐induced desorption mass spectrometry (PDMS) has been used to follow the modification of chrysotile asbestos fiber with organosilane compounds. Monitoring changes in the peak area ratios of Si+, Mg+ and SiOH+ ions in PDMS and atomic ratios from XPS, the formation of organosiloxane polymers vertical to the surface is suggested. Changes in the ratios also indicate differing coverages of the modifiers, owing in part to steric effects associated with the different organic substituents. The fibrous, non‐conductive nature of the sample did not impair the analysis with 252‐Cf PDMS. This application lends further support to the belief that PDMS is a surface‐sensitive technique.
Investigation of gallium arsenide multilayer structures using a tunnelling microscope combined with a UHV‐SEM
Authors: Albrektsen O. , Salemink H. 
Published: December 2004

AbstractAnalysis of semiconductor multilayers in an ultrahigh vacuum (UHV) environment is performed using a tunnelling microscope built into a UHV‐SEM with an Auger facility. The GaAs (110) surface is investigated with tunnelling spectroscopy and topography. As this cleavage plane is perpendicular to the preferential 〈001〉 growth direction, several material properties along the growth direction can be monitored with atomic resolution. The system is equipped with an interlocked preparation chamber for UHV cleavage of samples and for preparation of tunnelling tips, which subsequently are transferred into the scanning tunnelling microscope (STM). The SEM is used to select the sample area for the STM, with a resolution of 25 nm. Examples of results are the tracing of p‐n junctions in (Al)GaAs heterostructures and the valence band alignment in GaAs/AlGaAs interfaces. Typically, these results are obtained with a spatial resolution of 1.0–1.5 nm and are compared with results from conventional experiments (luminescence or C–V measurements), which pertain to much larger sample areas. Finally, we discuss recent results on cross‐sections of MBE‐grown (Al)GaAs multilayers, with atomic resolution in the epitaxial layers and in their interfaces.
EELS and low‐energy electron emission of clean and oxygen‐exposed tantalum
Authors: Palacio C. , Martínez‐Duart J. M. 
Published: December 2004

AbstractThe electron energy‐loss spectra (EELS) associated with 4f and 5p excitations, and the secondary electron spectra (SES) have been used to study the oxidation of a clean polycrystalline tantalum surface. For the clean and oxygen‐exposed surfaces, the EELS results are discussed in terms of bulk and surface plasmons as well as interband transitions to unoccupied states above the Fermi level (EF). The secondary electron spectra have been used as a fingerprint for the density of unoccupied states above EF. The changes observed in the EEL spectrum upon oxygen exposure are explained as being due to oxide formation, in agreement with previous results by XPS and AES. The features observed above the NVV and OVV Auger transitions, in both the clean and oxidized surfaces, are described as auto‐ionization emission due to the decay of electrons that have been excited resonantly from the 4f and 5p levels to states well above the states well above the Fermi energy. The excitation process has been identified also in the EEL spectra.
Intercomparison of surface analysis of thin aluminium oxide films
Authors: Olefjord I. , Mathieu H. J. , Marcus P. 
Published: December 2004

AbstractA round robin test organized by the European Federation of Corrosion (EFC) Working Party on Surface Science and the Mechanisms of Corrosion and Protection, supported by the European Community Bureau of References (BCR), and further extended under VAMAS (Versailles Project on Advanced Materials and Standards), has been performed. The aim of the test was to study the reproducibility of surface analyses in different laboratories on well‐documented samples by ESCA and Auger spectroscopy. The reference material is aluminium, oxidized at 250°C in oxygen. Test samples were distributed to 22 laboratories in Europe, North America and Japan. Data have been received from 20 laboratories.The test results collected are: peak positions, intensities, chemical shifts. The reference energies of the ESCA spectrometers are 84.0 eV for Au 4f7/2 and 932.7 eV for Cu 2p3/2. The binding energies of the metallic states of Al 2p and Al 2s are 73.0 (±0.1) eV and 118.0 (±0.2) eV, respectively. The chemical shifts of Al3+ in the oxide layer are 2.8 (±0.1) eV and 2.5 (±0.1) eV. The oxygen content of the oxide layer, measured by nuclear reaction analysis, is 16.3 × 1015 atoms cm−2. This corresponds to an oxide thickness, d, of 23 (±1) Å. The value of d/λ (λ is the attenuation length) calculated from the measured ESCA intensities is 1.13 (±0.03) for Al 2p with an Mg Kα x‐ray source, taking into account the take‐off angle. The values of the attenuation length obtained for Al2O3 are λ(Al3+) Mg Kα = 20.2 (±2.0) Å and λ(Al+3) Al Kα = 24.8 (±3.3) Å. The ratios of the photoelectron yields of oxygen and aluminium are Y(O1s)/Y(Al2p) = 6.2 (±0.8) and Y(O1s)/Y(Al2s) = 5.4 (±0.8) with an Mg Kα x‐ray source and Y(O1s)/Y(Al2s) = 6.6 (±0.6) and Y(O1s)/Y(Al2s) = 4.9 (±0.5) with an Al Kα x‐ray source.The LMM and KLL AES energies of Al in Al2O3 are 53.4 (±2.8) eV and 1389.4 (±3.5) eV, respectively. The corresponding values for aluminium metal are 66.4 (±2.7) eV and 1394.4 (±4.0) eV. For thin films where the attenuation length is of the same order of magnitude as the film thickness, an exponential fit of the experimental depth profile is proposed. The ratio of the sputtering rates of Al2O3 and Ta2O5 is thus found to be 0.72 (±0.14).The consistency between measurements performed in the different laboratories is excellent in many instances but certain problems are identified, which would deserve further work.
Quantitative AES and XPS: Determination of the electron spectrometer transmission function and the detector sensitivity energy dependencies for the production of true electron emission spectra in AES and XPS
Authors: Seah M. P. , Smith G. C. 
Published: December 2004

AbstractFor the use of published general or theoretical sensitivity factors in quantitative AES and XPS, the energy dependence of both the spectrometer transmission function and the detector sensitivity must be known. Here, we develop simple procedures that allow these dependencies to be determined experimentally. Detailed measurements for a modified VG Scientific ESCALAB II, the metrology spectrometer, operated in both the constant ΔE/E and constant ΔE modes, are presented and compared with theoretical estimates. It is shown that an exceptionally detailed electron‐optical calculation, involving proprietary information, would be required to match the accuracy of the experimental procedures developed. Removal of the spectrometer transmission function and the detector sensitivity terms allow the measured spectrum to be converted to the true electron emission spectrum, irrespective of the mode of operation. This provides the first step to the provision of reference samples to calibrate the transmission functions and detector sensitivities of all instruments so that they, in turn, may produce true electron emission spectra. This is vital if: (1) all instruments are to give consistent results; (2) theoretical terms are to be used in quantifying either AES or XPS; (3) reference data banks are to be established for AES or XPS.
Correcting the depth profiles broadened by the crater effect: A numerical procedure
Authors: Weiss Zdeněk 
Published: December 2004

AbstractConcentration–depth profiles which are distorted by the crater effect exhibit a special relationship between the concentration vs. depth distribution and the measured signal vs. time response. This relation is given by a linear Volterra integral equation of the first kind with the kernel which can be experimentally evaluated. A numerical procedure is described for the profile correction by solving that equation, along with discussion of existence, uniqueness of the solution and convergence of the approximations to the original profile.
Optimization of rotational Auger depth profiling
Authors: Tanemura M. , Aoyama S. , Okuyama F. 
Published: December 2004

AbstractThe dependence of depth resolution on the rate of sample rotation in rotational Auger depth profiling was systematically investigated for Cu/Fe multilayer films, using 1–3 keV Ar+ and Xe+ ions as projectiles. Except for Xe+ ion bombardment at 1 keV, the depth resolution was invariably improved by increasing the rate of rotation up to a critical value. The resolution improvement was more pronounced for Ar+ sputtering, but at and above the critical rate the resolution was nearly constant, independent of the sputtering conditions. The critical rotation rate depended on ion species and energy, decreasing with lowering ion energy and increasing ion mass. For 1 keV Xe+ the depth resolution obtained without rotation was comparable to that obtained with sample rotation, indicating that sample rotation was not the sole means to attain high depth resolution. As confirmed by scanning electron microscopy, highly resolved depth profiles for rotated samples were due mainly to reduced surface roughening. Evidence is also presented that at the critical rate of rotation the depth resolution was limited by the intrinsic interface roughness.
Performance of MgO/Au cermet films as secondary electron emission cold cathodes
Authors: Ritz Victor H. , Shih Arnold , Sobocinski Brian 
Published: December 2004

AbstractThe performance of MgO/Au cermet films as secondary electron emission cold cathodes was tested in a crossed‐field amplifier (CFA) tube until it showed signs of cathode insufficiency. Only 5–25% of the original cermet thickness (4000 Å) was left. Although heavy C coverage was observed, which degraded the secondary electron emission (delta), the primary cause of tube failure was the erosion of the cermet film under electron and ion bombardment. The mechanism and dissociation rate for MgO was determined in electron‐stimulated desorption measurements. A threshold for O+ ion desorption at the Mg 2p level demonstrated that MgO dissociates by the Knotek‐Feibelman mechanism with a yield of 1 × 10−7 O+ ions desorbed per incident electron. Various aspects of cathode erosion during CFA operation were considered and evaluated using a combination of experimental data and theoretical calculations. The results indicate that electrons and ions are both important sources of film erosion and limit the use of MgO/Au cermet films in practical CFA tube applications.
Determination of arsenic distribution across SiO2/Si interfaces with secondary ion mass spectrometry, using Ar+ bombardment and the internal indicator method
Authors: Michiels F. , Butaye L. , Adams F. , Simons D. 
Published: December 2004

AbstractThe quantification of arsenic in SiO2/Si interfaces is hindered by matrix effects that influence the sensitivity of the impurity elements in the interface. Moreover, ion‐ and electron‐enhanced segregation, charging effects and mass interferences further complicate the analysis. The suitability of the internal indicator method to account for the variation of the sensitivity of arsenic while profiling through SiO2/Si interfaces was evaluated. Although the method does not provide a comprehensive answer to all problems, the feasibility of the methodology was demonstrated. Arsenic was foundd to be enriched in the Si phase by a factor of ∼4000.
Small‐area XPS and XAES study of early iron metallurgy slags
Authors: Ingo G. M. , Scoppio L. 
Published: December 2004

AbstractA group of slags dating back to Iron Age II (Aramean Period, 800–720 BC), which appeared to be iron‐smelting by‐products, has been found at Tell Afis (Northwestern Syria). The chemistry of these materials has been studied by means of small‐area x‐ray photoelectron spectroscopy and x‐ray‐induced Auger electron spectroscopy. The results indicate that the slags can be associated with an iron smelting process and show the presence of large amounts of FeO1−x′, Fe3O4 and FeOOH mixed with different aluminium and silicon compounds. As evidenced by the Wagner two‐dimensional chemical‐state plots of silicon and aluminium, these latter consist essentially of quartz and various silicates, such as wollastonite, Mg[SiO4] or Mg[SiO6] compounds, melilite and other complex aluminosilicates. Chemical information agrees with the predictions of the model of early iron‐making furnaces and is used to elucidate some aspects of the early iron‐making process.
The depth distribution function in Auger/XPS analysis
Authors: Dwyer V. M. , Richards J. M. 
Published: December 2004

AbstractAn analysis of a recent three‐exponential approximation of the depth distribution function (DDF) for quantitative Auger/XPS analysis is presented and a comparison is made with an exact DDF obtained for an analytical solution to the Boltzmann transport equation in the transport approximation. Several problems with the approximate DDF are identified and, using the derived analytical form, an alternative two‐exponential DDF is suggested.
In situ measurements of the porosity on thin oxide films by IR emission spectrometry
Authors: Pigeat P. , Pacia N. , Weber B. 
Published: December 2004

AbstractObservation of the normal spectral emissivity is used as a method of in situ surface investigation. This technique has been used here to follow tungsten oxidation during reactions performed under 1.3 Pa of oxygen both above and below the temperature of the phase transition: ortho‐rhombic αWO3 → tetragonal α′WO3.We show that the difference between the observed radiative behaviour is due to the difference between the morphology of these oxides (αWO3 is homogeneous and α'WO3 is porous).From this difference, with an optical model using an effective medium theory (Bruggeman equation), we show that it is possible to describe correctly the experimental measures and to calculate the value of the porosity of the film during its growth. In this model, we show that the best value of the depolarization factor for the oxide particles is 1/3. This is precisely the value that characterizes a porous deposit where the particles (here, oxide particles) are spherical; it is also a good approximation for particles deprived of a particular shape (geometrically isotropic) and disposed at random, such as what we have effectively observed by scanning electron microscopy.
Analysis of polymer surfaces by SIMS 17. An assessment of the accuracy of the mass assignment using a high mass resolution ToF‐SIMS instrument
Authors: Reichlmaier S. , Hammond J. S. , Hearn M. J. , Briggs D. 
Published: December 2004

AbstractThe prospects for obtaining highly accurate mass assignments in polymer surface studies using state‐of‐the‐art time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) have been investigated systematically. For a thick film of poly(ethylene terephthalate) (PET), the reproducibility of mass measurement in both positive ion (range m/z = 0–600) and negative ion (range m/z 0–350) modes has been studied in statistical fashion over a period of several months. Glyceryl monostearate, representing a typical polymer additive, was studied both on PET and as a very thin film on aluminum in order to compare the behavior of insulating and conducting samples. The effect of different mass calibration strategies (including use of atomic and molecular species), mass interferences and metastable peaks on mass accuracy also have been investigated. Finally, the importance of peak intensity for mass resolution and achievable mass accuracy has been determined. The results show that a useful mass accuracy of better than 20 ppm can be achieved over a mass range m/z = 0–600 for these polymer film surface studies under routine operating conditions.
The infinite velocity method: A new method for SIMS quantification
Authors: Van Der Heide P. A. W. , Zhang Min , Mount G. R. , McIntyre N. S. 
Published: December 2004

AbstractTwelve elements spanning a mass range of 197 atomic mass units from five standard reference materials and three implant materials were analysed to ascertain the validity of a new method, termed the infinite velocity method, for quantifying the negative monatomic secondary ion emissions resulting from Cs‐bombarded surfaces. This method extracts quantitative data by extrapolating secondary ion yield versus kinetic energy data to the infinite velocity limit. Extrapolation to infinite velocity is done because matrix effects are theoretically predicted to be removed at this limit. Plotting the extrapolated data against known concentrations for the homogeneous standard reference materials yielded linear standardization curves for all elements analysed, indicating that the matrix effect is indeed removed, i.e. sensitivity factors were not required. Likewise, the resulting concentration profiles of the implant materials analysed agreed well with concentration profiles calculated via the integration method. Thus, samples can be quantified by this procedure without the requirement for matrix‐matched calibration materials. Theoretical implications and the assumptions used in the calculations are also discussed.