bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vertical differential charging in monochromatized small spot X‐ray photoelectron spectroscopy
Authors: Yu Xiang‐Rong , Hantsche Harald 
Published: May 2005

AbstractDifferential charging (DC) is a charging effect in x‐ray photoelectron spectroscopy (XPS or ESCA) that results from the spatial variation of sample potentials in the XPS sampling volume. It can be conceptually categorized into two different aspects—lateral (LDC) and vertical (VDC)—according to the difference in the directions of the inhomogeneous distribution of the potentials in the surface phases of the sample. The phenomenon of VDC, which leads to a shift of the peak position, to a broadening of the peak width or even to a dramatic distortion of the peak shape, was observed in the following systems: semiconductors and conductors with ultrathin oxidized or insulating overlayers. The suggested approach to overcome the problem of VDC is simply to isolate the sample and neutralize it with electrons from a monoenergtic flood gun.
Description of the influence of elastic scattering of electrons in the specimen and in an adventitious hydrocarbon overlayer on photoelectron signals by effective values of the inelastic mean free path and the asymmetry parameter
Authors: Ebel H. , Ebel M. F. , Svagera R. , Pöhn C. , Jablonski A. 
Published: May 2005

AbstractThe influence of elastic scattering of photoelectrons in the substrate and in an adventitious hydrocarbon overlayer on the effective inelastic mean free path and the effective asymmetry parameter has been investigated by Monte Carlo calculation. The results are representative of 27 chemical elements, asymmetry parameters 0.6 ⩽ β ⩽ 2.0, kinetic electron energies 300 ⩽ Ekin ⩽ 1500 eV and overlayer thicknesses 0 ⩽ t ⩽ 26.6 Å. For an application in quantitative surface analysis by XPS we propose the use of the effective inelastic mean free path (0.951 IMFP, tabulated values) and the effective asymmetry parameter βeff. The calculation of βeff is performed by tabulated values of β, inelastic mean free paths and measured reduced thicknesses of the hydrocarbon layer.
Carbonization of candidate high‐temperature matrix materials for carbon/carbon composites
Authors: Pehrsson Pehr E. , Armistead Paul , Sastri Satya 
Published: May 2005

AbstractCarbon precursors used for preparing carbon/carbon composite (CCC) matrix binders undergo component elimination and carbonization during heating, which affects the ultimate carbon product. We analyzed the structural and compositional changes of two polymeric precursors N,N′‐(1,3‐phenylenedimethylidene)bis(3‐ethynylaniline) and 4,4′‐bis(3,4‐dicyanophenoxy)biphenyl during high‐temperature annealing under inert atmosphere. The samples were analyzed using x‐ray diffraction, x‐ray photoelectron spectroscopy and microRaman scattering. The precursor molecules cross‐link during curing and annealing, to form glassy carbons. The carbon structure after the annealing was reflected by the high oxidizability of the carbon in air. Deconvolution of the C 1s and O 1s XPS spectra showed that the surface oxygen was present primarily as hydroxyl and carbonyl groups, and that the amounts of surface oxygen correlated with the extent of graphitization. Addition of iron in the form of ferrocene in the precursor accelerated graphitization at all temperatures. The results are compared to those for other polymer precursors and graphite.
Testing the success of analytical image correction routines: Surface images
Authors: Barkshire I. R. , Walton J. M. , Prutton M. 
Published: May 2005

AbstractMultispectral techniques in Auger microscopy involve the acquisition of data as several spatially registered images or signals from the Auger, specimen absorption current, characteristic x‐ray, backscattered and secondary electron signals. Each signal contains information from different interactions and volumes within the sample. Various combinations of these signals can be used along with simple physical models to remove those contrast variations in Auger images that are not due to compositional variations of the sample within the Auger escape depth. Such contrast may, for example, be due to beam current fluctuations during data acquisition, substrate backscattering or topographical effects. To measure the success of these corrections, two tests have been devised: the calculation of the number of resolvable levels in the Auger image before and after correction; and the measurement of the modulus of correlation |CAR| between the corrected Auger image and the correction factor image. The tests may be used to evaluate any new image correction method. They have been applied to simulated and experimental data for a sample with varying subsurface composition. The results show that both tests are useful for evaluating the accuracy of a correction, and that measurement of |CAR| is the more sensitive test.
The application of chemical state AES and SAM to the examination of spray‐formed aluminium alloy fracture surfaces
Authors: Baker M. A. , Tsakiropoulos P. 
Published: May 2005

AbstractThe fracture surface of a spray‐formed Al‐5.2Cr‐1.4Zr alloy has been examined using AES and scanning Auger microscopy (SAM). Cratered regions of the surface were identified and high‐energy resolution AES analysis showed a localized 20 Å thick Al2O3 film to be present in these areas. Chemical‐state imaging of the Al fracture surface enabled the local distribution of oxide to be determined. The surface topography was not found to be suppressed using the standard (PB)/B or (PB)/(P + B) correction algorithms. This point is discussed with consideration of the electron emission from such highly structured surfaces. The oxide thickness measured from the craters is in good agreement with that previously determined by XPS for powder particles produced in the atomization process. Crater formation is suggested to occur as a result of complete powder particle solidification prior to the particles impacting the substrate/deposit. The localized oxide, revealed by fracture, presents areas of weakness in the unworked material.
Effects of crystallinity on depth resolution in sputter depth profiles
Authors: Hösler W. , Pamler W. 
Published: May 2005

AbstractFor sputter depth profiling the effect of the layer crystallinity on the resolution of the underlying interfaces was investigated. By applying D. Onderdelinden's model of monocrystal sputtering (Appl. Phys. Lett. 8, 189 (1966); Can. J. Phys. 46, 739 (1968)) and J. Lindhard's approach to axial ion channelling (Phys. Lett. 12, 126 (1965); K. Dan. Vidensk. Selsk. Mat. Fys. Medd. 34, No. 14 (1965)) to textured and non‐textured polycrystalline layers, it is shown that the interface resolution under these layers is largely affected by the channelling of incident ions. The strong dependence of channelling on the orientation of individual grains leads to extremely non‐uniform erosion and poor interface resolution. This model of polycrystalline layer sputtering reproduces well the dependence of depth profile shape and depth resolution on layer thickness, ion energy and incidence angle, as shown for sputter depth profiling through textured aluminium layers by inert gas ions. In the case of higher ion masses, the observed effects are slightly overestimated by the model, as anticipated from the inherent limitations of the Lindhard and the Onderdelinden approaches. The implications of channelling for depth profiles of polycrystalline layers are discussed and conclusions are drawn for appropriate selection of sputter parameters to ensure optimum depth resolution. The effects of sample temperature, continuous rotation of the sample during sputter erosion and reactive ion sputtering are also discussed.
Coincidence measurements in the electron spectroscopies: Surface studies
Authors: Thurgate S. M. 
Published: May 2005

AbstractCoincidence techniques have been fruitfully employed in many areas of physics. They are now beginning to be used in the study of surfaces. In electron spectroscopy, their appeal is that they can be used to distinguish between processes, and, in some cases, to completely describe single events.The interaction between surface atoms and electrons is complex, with many possible interactions. The coincidence technique can be used to reduce the number of possibilities and so to produce spectra that are more easily interpreted. However, the high density of atoms on a surface necessarily means that there is a high density of emitted inelastic electrons that appear as background in the spectra. These, and other effects, make it difficult to perform coincidence spectroscopy from surfaces, which explains why there have been relatively few experiments undertaken to date.The progress in developing coincidence experiments is reviewed, along with a description of the understanding that has come from it.
Semiconductor surface layer analysis based on reflectometry
Authors: Jezierski K. , Misiewicz J. , Gumienny Z. , Heiman D. 
Published: May 2005

AbstractAn experimental set‐up for reflectance spectra measurements is presented. It is characterized by a high degree of precision, normal incidence of light and an energy range of 2‐6 eV. Computer analysis of the reflectance spectra is described. A multilayer model of the suface layer as well as the effective medium approximation theory are used. Results for implanted GaAs and for epilayers ZnSe/Zn3P2 are discussed.
SIMS Profile quantification by maximum entropy deconvolution
Authors: Allen P. N. , Dowsett M. G. , Collins R. 
Published: May 2005

AbstractThe action of the probe ions in SIMS depth profiling causes a number of mass transport phenomena. Consequently the data obtained are both broadened and shifted in a manner dependent on the species of the matrix, impurity and probe, and the experimental conditions. Quantification methods based on implanted standards and crater depth measurement are hampered by inaccuracies in the depth measurement, and take no account of the blurring processes. This paper reports the development of an alternative method. The blurring processes are not yet well enough understood for complete modelling. An empirical model, valid in the dilute limit, is that the true depth distribution is convoluted with an instrumental response to give the SIMS signal. If the response function is carefully defined, inversion of the convolution equation should give a fully quantified depth profile, correcting for blurring effects and any differential shift, mapping primary ion dose density (or time) back to depth and mapping signal intensity back to concentration in one mathematical operation. The sample from which the response function is measured becomes a complete concentration and depth standard. Deconvolution is non‐trivial as there is no unique solution in the real case, where the profile data and measured response consist of a finite number of data points. The method used here is based on the use of maximum entropy and returns the least biased (least structured) of the possible solutions. The use of this method to fully quantify two samples will be demonstrated and the results compared with ordinary quantification.
Enhanced SIMS analysis performance by CCl4 flooding technique
Authors: Gao Y. , Migeon H. N. , Juhel M. , Lecart J. 
Published: May 2005

AbstractThe CCl4 flooding technique combined with oxygen ion bombardment has been used during SIMS analysis. The secondary ion yield and the matrix effect have been investigated. The results have been compared with those obtained under oxygen bombardment or under oxygen bombardment plus oxygen flooding. We show that this simple technique allows a significant enhancement of ion yield for all the elements studied and induces a weak matrix effect.
Passive film composition and pitting behaviour of Fe–25Cr–11Nb studied by scanning Auger microscopy
Authors: Hubschmid C. , Mathieu H. J. , Landolt D. 
Published: May 2005

AbstractScanning Auger microscopy has been applied to the characterization of passive films formed on an Fe–25Cr–11Nb model alloy having a dendritic structure. The composition of the passive film is spatially non‐uniform and reflects the phase structure of the alloy. The Fe–25Cr–11Nb alloy exhibited a better resistance to pitting than a binary Fe–25Cr alloy. This is due to the fact that, on one hand, niobium improves the pitting resistance of the niobiumrich phase while, on the other hand, the pitting resistance of the niobium‐poor phase is enhanced by chromium segregation.
Quantification of SIMS data for multicomponent glasses
Authors: Bojan V. J. , Büyüklimanli T. H. , Pantano C. G. 
Published: May 2005

AbstractFracture and commercial float glass surfaces have been analyzed in a Cameca IMS‐3f spectrometer using 18O− bombardment. Sample charging was controlled through the use of different combinations of a gold grid and thin gold coating. Depth profiles have been quantified with relative sensitivity factors (RSFs) that were determined from fracture surfaces of float glasses of known composition. The sodium and potassium RSFs have been found to be more sensitive to the method of charge compensation than the RSFs of the other elements in the glass. The integrity of the sodium signal is not guaranteed by the presence of a grid on the sample surface. Depth profiles of fracture surfaces show unexpected gradients that can extend to 100 nm, complicating the interpretation of profiles obtained from manufactured surfaces. The calculation of the atomic fraction of all the elements in the glass is difficult within ∼300 nm of the surface owing to effects from the measured oxygen signal. Fortunately, the composition of the glass as expressed in mole percent of the oxides is more reliable, but still not free of artifacts. The results of these studies and those performed on similar glasses and materials in other laboratories suggest that, regardless of the primary beam, fracture surface analysis should precede the analyses of treated surfaces, especially if quantitative information is required within 100 nm of the surface.
On the applicability of tougaard background subtraction to general auger spectra
Authors: Bender Hugo 
Published: May 2005

AbstractThe Tougaard inelastic background subtraction algorithm is applied to the Auger spectra of a set of elemental standards including all kinds of Auger transitions. The problems occurring with certain transitions are discussed. The relative area sensitivity factors are calculated and compared with the sensitivity factors in differential mode and with theoretically calculated Auger yields. The relative sensitivity in direct mode using full peak integrations is larger than in differential mode. The experimental area sensitivity agrees remarkably well with theoretical predictions.
Auger electron angular distributions from Pt(111): The effect of adsorbed iodine monolayers
Authors: Doyle Charles A. , Chyan Oliver M. R. , Frank Douglas G. , Hubbard Arthur T. 
Published: May 2005

AbstractComplete Auger electron angular distributions have been measured from a Pt(111) substrate in the presence and absence of three distinct iodine adlattices in order to investigate the effect of adsorbate layer structure on substrate emission. The adlattices investigated were Pt(111)(□3 × □3) R30°‐I, Pt(111)(□7 × □7)R19.1°‐I and Pt(111)(3 × 3)‐I. Three Pt Auger transitions were employed (65, 258 and 1968 eV) to explore the effect of Auger electron kinetic energy. For each kinetic energy investigated, the qualitative features of the substrate angular distributions were the same in the presence and absence of the iodine overlayer, although small quantitative differences were observed. An energy‐dependent quantitative effect was also observed, in which the absolute intensities of the distributions were attenuated substantially at lower kinetic energies but were relatively unaffected at higher kinetic energies. These results show that lower kinetic energy Auger electron angular distributions (<300 eV) are relatively sensitive to the presence of the adlattice, although careful quantitative measurements and analyses are required to observe the differences in the distributions. The origin of attenuation features in the distributions is not yet fully understood, and further experimental and theoretical development is required to relate the observed attenuation features to the surface structure.
Electronic structure and work function study of a model dispenser cathode surface
Authors: Lamouri A. , Krainsky I. L. , Müller W. 
Published: May 2005

AbstractWe have used work function measurements (Δϕ), Auger electron spectroscopy, low‐energy electron diffraction and angle‐resolved inverse photoelectron spectroscopy to study the coadsorption of barium and oxygen on tungsten. The experimental two‐dimensional band structure was compared with results of embedded cluster model calculations for a c(2 × 2) BaO monolayer on W(001) with barium and oxygen placed on alternate fourfold‐hollow sites. Our work function measurements revealed that adsorption of one monolayer of BaO decreased the work function of W(001) (ϕ = 4.63 eV) to ∼ 2.3–2.4 eV regardless of the order of barium and oxygen adsorption on the surface. Inverse photoelectron spectroscopy in the isochromat mode was used to investigate the unoccupied electronic energy levels of one monolayer of BaO on W(001) along two high‐symmetry directions of the W(001) surface Brillouin zone. Non‐dispersing spectral features were observed at 0.6 eV and 3.4 eV above the Fermi level (EF) and were assigned to transitions into both barium and tungsten d states in good agreement with calculated densities of states.
Maximum entropy quantification of SIMS depth profiles—behaviour as a function of primary ion energy
Authors: Allen P. N. , Dowsett M. G. 
Published: May 2005

AbstractPrevious publications have proposed the use of reconstruction as a method of quantification of SIMS depth profiles, taking the convolution integral as an approximate model for the measurement process in the dilute limit. We present here a demonstration of the maximum entropy (MaxEnt) reconstruction method for SIMS depth profile quantification at a number of primary ion energies. Neither implanted standard nor crater depth measurement are required by the technique, although both are used here as comparisons. The erosion rate calculated directly from the delta layer is found to be equivalent to that from crater depth measurement to within experimental accuracy. It is demonstrated that the MaxEnt reconstruction method can quantify a delta layer in ideal circumstances, remoing all energy‐dependent effects. For another sample (a set of three alleged delta layers) the MaxEnt reconstruction method is found to yield improvements in depth resolution at all energies, removing the energy dependence of the rise and decay slopes and almost halving the measured feature widths (full width at half‐maximum). This improvement in accuracy in quantification has enabled us to analyse more critically the sample, demonstrating that the layers had finite widths, a fact that was not evident from conventional quantification methods.
Characterization of a range of alkyl‐bonded silica HPLC stationary phases: XPS and ToF‐SIMS studies
Authors: Brown V. A. , Barrett D. A. , Shaw P. N. , Davies M. C. , Ritchie H. J. , Ross P. , Paul A. J. , Watts J. F. 
Published: May 2005

AbstractA series of alkyl‐bonded silica HPLC stationary phases with a mean particle diameter of 5 μm has been prepared using a variety of dimethylalkylsilyl chlorides (i.e. monofunctional bonding agents) with alkyl chain lengths varying from C1 to C18, including phenyl and cyanopropyl groups. The stationary phases have been characterized using XPS and time‐of‐flight (ToF)‐SIMS. Elemental analyses by XPS have identified trace quantities of iron, sodium and chlorine at the silica/dimethylalkylsilyl chain interface, and aluminium was detected by ToF‐SIMS. A comparison of percentage carbon obtained by XPS with bulk carbon‐loading analyses suggests that the alkyl chains are bonded to the surface of the porous silica particles. Molecular ions characteristic of the dimethylalkylsilyl groups were identified in the ToF‐SIMS data together with ions attributable to these alkylsilyl groups attached to fragments of silica, the latter indicating covalent bonding to the silica surface. In addition, a series of low‐mass signals corresponding to alkyl chain fragments and silyl/silica‐based ions was observed. The value of high‐resolution ToF‐SIMS data for ion assignments is well demonstrated. The relative ion intensities of several of these low‐mass ions were studied as a function of changing alkyl chain length. In general, as the alkyl chain length increased, the abundance of the silicon‐containing fragments decreased, whilst the abundance of the alkyl‐based fragments increased, within the ToF‐SIMS spectra.
Comparative in situ ToF‐SIMS/XPS study of polystyrene modified by argon, oxygen and nitrogen plasmas
Authors: Petrat F. M. , Wolany D. , Schwede B. C. , Wiedmann L. , Benninghoven A. 
Published: May 2005

AbstractThe on‐line combination of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and monochromatized photoelectron spectroscopy is a valuable analytical tool for the characterization of chemically modified surfaces. By an in situ combination of these techniques with a plasma modification chamber, we have investigated polystyrene surfaces modified by various kinds of microwave plasmas (argon, oxygen and nitrogen).The modified surfaces are widely different with respect to the incorporation of elements originating from the plasma, the degree of chemical changes caused by the plasma and the plasma‐induced etching rate. Significant formation of new functional groups specific for the plasma gas is only observed for nitrogen and oxygen. As compared to nitrogen and argon, treatment with the oxygen plasma leads to a high etching rate, but only moderate changes of the chemical state of the polymer surface. In all cases, severe degradation of the aromatic system occurs.Exposure to air after plasma treatment leads to the uptake of considerable amounts of oxygen. In the case of the oxygen and argon plasma, the high mass resolution of ToF–SIMS allows the identification and distinction of clusters that are specific for the oxygen incorporated during plasma treatment and those appearing during exposure to the atmosphere.
E‐Beam SNMS: A complementary surface analysis technique
Authors: Bayly A. R. , Wolstenholme J. , Petts C. R. 
Published: May 2005

AbstractSputtered neutral mass spectrometry (SNMS) with ionization by low‐energy electron beam offers several analytical advantages that complement the capabilities of the major surface analysis techniques: XPS, AES and SIMS. These include easy operation on insulator specimens, reduced influence of topography or sample tilt, low spread of elemental relative sensitivity factors (RSFs) across the periodic table, near‐constant RSFs in different matrices and hence quantification from 100% down to trace concentrations, ppm detection limits, microprobe operation for depth profiling and submicron imaging and depth resolutions as for SIMS (≥1 nm). In addition to these analytical performances, the equipment shares much in common with quadrupole SIMS facilities and, as with that technique, is easily integrated into multitechnique instruments.This paper compares performances of SNMS and SIMS on the same samples and presents some imaging and useful yield data from a close‐coupled ionizer, which is a new development on the 410 SIMSLAB. Comparisons are also made between, SIMS, SNMS and AES.