Search

High-priority industrial nanomaterials like SiO2, TiO2, and Ag are being characterized on a systematic basis within the framework of the EU FP7 research project NanoValid. Silica nanoparticles from an industrial source have been analyzed by Auger electron spectroscopy. Point, line, and map spectra were collected. Material specific and methodological aspects causing the special course of Auger line scan signals will be discussed. Copyright © 2014 John Wiley & Sons, Ltd.

A technique of phase identification from the characteristics of electronic structures is established by Auger electron spectroscopy. GaN epilayers in wurtzite and zinc-blende polytypes are used for practical investigations. Auger spectra show phase-dependent energetic shifts and peak intensity variations. Simulation of theoretical spectra reveals the substantial correlation of the Auger line shape with the bonding electronic states. This approach demonstrates the correspondence between electronic structure and atomic structure and hence provides criteria for phase identification.

The O K-LL spectrum from a SiO 2 surface was measured in coincidence with O 1s photoemission in SiO 2 . The coincidence lineshapes are compared to the simultaneously obtained conventional Auger lineshapes and to model lineshapes. The low-energy tail of the O K-LL lineshape from SiO 2 is suppressed in the APECS spectrum due to discrimination against extrinsic loss and initial-state shake processes, but remaining intensity indicated significant contribution from final-state shake-up/off processes. The results also confirm that a low energy satellite to the O K-L 2,3 L 2,3 Auger line that is eliminated in the coincidence spectrum, and a high-energy shoulder that is enhanced in the coincidence spectrum, arise from an initial-state shake process, and final-state correlation effects, respectively. The results demonstrate the viability of applying APECS to the study of other metal oxides via the anion.

The M 3 –VV Auger-photoelectron coincidence spectroscopy (APECS) spectrum of Cu(100) and the L 3 –VV APECS spectra of Cu metal and CuOx/Cu surface are analyzed in detail. The narrowing and energy shift of the photoelectron line in the M 3 –VV APECS spectrum is well predicted by the present theory. The spectrum shows the presence of the M 2 –M 3 (V)–VV(V) decay in which a hole in the 4s band hops away prior to the decay of M 3 hole. The analysis of the L 3 photoelectron spectra of Cu metal measured in coincidence with the 3 F or 1 G Auger line raises a question concerning the presence of two different core–hole states upon the L 3 level ionization recently proposed by Thurgate and Jiang [Surf. Sci. 466 (2000) L807]. The analysis of the L 3 –VV APECS spectrum of CuOx/Cu shows that the final-state charge–transfer interaction plays an important role in CuO.

MVV spectra of Rh, Pd, and Ag were measured with and without ionization of their L3 levels. Extra (MMMVV) structure corresponds to the M45M45-->M45VV transition following the L3M45M45 transition. We interpret the MMMVV structure for Pd as quasiatomic in nature from its similarity to the corresponding Ag spectral shape and from its agreement with atomic calculations. The Pd quasiatomic MMMVV spectrum arises from a two final-state hole bound state in the Pd d band filled by screening of the core holes. These findings represent the first unambiguous observation of the influence of complete screening on spectral features.

In this paper we show results from resonant photoemission experiments where energy dispersive curves (EDC) were collected at various photon energies around the Si2p absorption edge. From the complete collection we have extracted the spectrum measured at the photon energy of 125 eV and studied the Auger feature included in the EDC. From the comparison of the Auger line of the bulk SiO 2 with the expected transitions we demonstrate the occurrence of inter-atomic transitions in the bulk oxide. Comparing the Auger line from the bulk oxide with that from a native oxide we may observe the occurrence of inter-atomic transitions localized at the interface. We propose an interpretation of this result by considering the geometry at the interface.

We compare nonrelativistic atomic multiplet calculations of the ${L}_{1,2,3}{M}_{4,5}{M}_{4,5}$ spectra of Rh and Pd in the jj intermediate-coupling scheme with high-resolution experimental spectra excited with a Ti anode, indicating general, good agreement even for these open valence shell metals: the simplicity of the calculations indicates their suitability for experimental analyses. Comparison with relativistic calculations, including configuration interaction, for Rh indicates that the nonrelativistic spectra appear to agree better with the experimental data than do the relativistic ones. The influence of relativistic and correlation effects on the intensities does not seem to be important. The major influence on the forms of the spectra is that of the relative positions of the multiplet components. Satellites of all three spectra would seem to be produced by shake-up, rather than Coster-Kronig processes. The positions and forms of these satellites are consistent with a model in which spectator vacancies in the $4d$ band exist in both the initial and final states of the Auger transition.

High-resolution Ag ${L}_{3}$-edge XANES for a series of Au-Ag alloys, ${\mathrm{AuAg}}_{3},$ AuAg, and ${\mathrm{Au}}_{3}\mathrm{Ag},$ have been obtained by monitoring the intensity of the highly energy-resolved Ag ${L}_{3}{M}_{4,5}{M}_{4,5}{(}^{1}{G}_{4})$ Auger line. The experimental results reveal features that were previously unresolved with total electron yield techniques and confirm previous observations that Ag gains d charge and Au loses d in Au-Ag alloys. Full-scale multiple scattering calculations for the Ag ${L}_{3}$-edge XANES of Ag and AuAg yield semiquantitative agreement with the experiment. The results show that in the case of wide band metals, the Auger yield of a well-separated narrow final state can indeed be used to improve the resolution of XANES near the threshold. The implication of the results to electron charge redistribution upon alloying is discussed.

The atomic and electronic structures of clean 6H–SiC(0001) surfaces have been investigated by means of LEED and photoelectron spectroscopies (XPS, XAES and UPS). First a clean surface having the (3 × 3) structure has been obtained by heating the sample at 800°C under a low Si flux. Successive annealings in UHV have produced two other stable reconstructions, namely the [Formula: see text] and the [Formula: see text]. The various surface structures show distinctive core-level and Auger line shapes, which are characteristic of the composition of the surface layer, as checked by the XPS intensities by two different excitation sources (Mg Kα and Zr Mζ), while UPS spectra show sizeable differences in the character of the valence bands. The evaluation of the atomic composition is able to sort between different models proposed in the literature.

The variation of the intensity of the Ne K - Auger line due to post-collision interaction has been measured as a function of the projectile energy at observation angle in 0.8 - 3.2 MeV - Ne collisions. The measured Auger-electron yield normalized to the theoretical or experimental total K-shell ionization cross section shows a strong enhancement when the projectile velocity is smaller than the Auger-electron velocity. The general agreement between the present experimental data and continuum distorted wave calculations provides a clear evidence that the observed impact-energy dependence is mostly due to the post-collision Coulomb focusing exerted by the projectile on the Auger electron.

We present the line shape analysis of the Si CVV transitions based on an extended Cini-Sawatzky approach, including overlap effects. We show that introducing an appropriate phase shift between the s and p tight binding basis orbitals of different atoms is essential to achieve agreement with experiment. The physical nature of this phase shift is discussed.

We measured the fine structure of the Cu L 3 M 4,5 M 4,5 Auger line excited by impact of MeV protons upon a Cu(110) surface. In case of a grazing incidence, a shift of the Auger line by 0.4 eV to higher kinetic energies is observed. This is attributed to a surface effect: The grazingly incident protons undergo semi-planar channeling at the surface and mainly excite Auger electrons at topmost surface layer atoms. Computer simulations which take into account surface steps corroborate this interpretation.

The growth at room temperature of K GaAs (110) and K Si (100) interfaces have been studied using Auger electron spectroscopy and principal component analysis. The PCA of the K Auger line of K GaAs (110) reveals the existence of three pure independent components. The splitting, without lineshape modifications, of the first two of them suggests the formation of complexes of different size at the surface. The third component has remarkable lineshape modifications with respect to the others and it is observed from the beginning of the evaporation process indicating the reactivity of the K GaAs (110) interface. This is not the case for the K Si (100) interface, where PCA only reveals the splitting of different sized complexes.

We investigate the influence of correlations among the valence-band electrons as well as correlations between valence-band and core electrons on the Auger line shape of solids. For metals with partially filled valence bands the relevant many-body problem is no longer exactly solvable. Usually, approximate solutions are constructed that correctly reproduce different exactly solvable limiting cases. We employ a diagrammatic vertex-correction method (three-particle ladder approximation) to calculate the three-particle Green function, which directly yields the Auger intensity. The validity of the approximation in limiting cases is discussed. It turns out that the three-particle ladder approximation gives correct results not only for those cases considered commonly but also for another limiting case: the limit of strong valence-band-core interaction. Numerical results for a model system indicate the approximation to be a very reasonable interpolation between the different limits.

Auger photoelectron coincidence spectroscopy has been used to study the intrinsic and extrinsic satellite contributions to the Ga L23M45M45 Auger line of GaAs. Data have been collected for the Ga L23M45M45 Auger line in coincidence with the 2p3/2 and 2p1/2 photoelectron lines from GaAs. The Ga 2p3/2 photoelectron line has also been collected in coincidence with the satellite on the lower kinetic-energy side of the Ga L23M45M45 Auger line. The relative contributions of the intrinsic loss processes is shown to be negligible, as expected, whereas the extrinsic loss function is shown to be a significant consideration when using these lines in quantitative analysis. No evidence is seen for a difference in the response of the Ga L23M45M45 final-state terms to the presence of a 3d hole at the surface and at the bulk as has been reported in the literature for the As M45VV line.

It is shown that Stokes doubling of an Auger line takes place when the frequency of the incoming X-ray photons is scanned near an X-ray absorption resonance. The conditions for observing Stokes doubling effects in Auger spectra are found to depend strongly on the form of the spectral function of the incoming X-ray photons. These conditions are quantified in the limiting cases of Lorentzian and Gaussian spectral functions.

We present high-resolution measurements of the natural Auger line shapes of the two highest-energy MNN lines of Ta, W, Pt, Au, Pb and Bi. It was found that all the lines studied are quite narrow, having a width of about 2 eV. The main lines are accompanied by smaller satellite peaks. While these measurements are very suitable for determining the natural line shapes, they are inadequate for obtaining the line intensities. The atomic sensitivities were therefore measured with a resolution of 0.4% of the Auger energy (somewhat better than the commonly available resolution). With this resolution it is impossible to resolve the fine structure of the lines and also gross errors are incurred in the measurements of the atomic sensitivities. We corrected these measured sensitivities by applying our theoretical analysis developed previously. The correction factors for the sensitivities are around 10. These large factors represent also the errors incurred in the as-measured sensitivities if no correction is applied. The detailed line shapes, as derived from the high-resolution measurements, and the corrected sensitivities, as obtained from our analysis, are the true characteristics with which any theoretical calculations of Auger transitions should be compared.

This paper reports the existence of an abrupt change in surface composition associated with a surface phase transition in a PbBiNi alloy. Equilibrium surface composition measurements on an alloy containing 5at% Bi and 0.04at% Ni, at temperatures from 460 to 560 K, have shown that the surface composition changes from a lead-rich to a bismuth-nickel-rich surface (or vice versa) in the range 500 to 525 K. Auger line scans performed with a high-resolution probe have shown that the transition proceeds by the formation and growth of bismuth-nickel-rich patches at the lead-rich surface, or vice versa, in the vicinity of the transition temperature.

The C-KLL Auger line shapes of the transition metal carbides and some related compounds are examined as a function of the metal and nonmetalloid components (C, N, and O). They are discussed in the context of hole-hole repulsion and screening effects. The effect of π versus σ-bonding and the proportion of ionic versus covalent bonding are correlated with various aspects of the X-CVV Auger line shape, such as relative peak shifts, intensity of a high energy shoulder, and the multiplet splitting of the sp component.

Specimens of Cr/AIN, TI/AIN, Ag/AIN, Cr/Si 3 N 4 and Ti/Si 3 N 4 interfaces were prepared by electron beam deposition. Auger spectra of as-deposited and annealed samples were obtained at their interfaces using JEOL JAMP10s. The overlapping spectra were separated by a subtraction technique. The subtraction was available for these systems. A change in Auger line shapes across the interface was observed and the interfaces were classified into two types: type A, the defect peak in the LVV Auger transition is constant across the interfaces and type B, the peak increases as the metal peak increases at the interface. The interfaces of Cr/AIN, Ag/AIN and Cr/Si 3 N 4 belong to type A. The interfaces of Ti/AIN and Ti/Si 3 N 4 belong to type B. AES results suggest that the substrate is reduced by the deposited metal at the Ti/AIN and Ti/Si 3 N 4 interfaces. This is supported by thermochemical data. It is suggested that the valence Auger analysis is applicable to the metal/ceramic systems as an evaluation method if the electronic dose is kept constant across the interface.

Correlation effects on the relative intensities and anisotropy coefficients of angular distribution and spin polarization of the Hg N6,7O4,5O4,5 Auger transitions have been investigated, applying the relativistic Dirac-Fock model with intermediate coupling. The results are discussed and compared with former calculations and experiments. In particular, the influence of e-e correlations has been taken into account, including initial and final state configuration interaction. A small influence of correlations in general has been found except for the energetically near-threshold Auger lines. A drastic effect has been found for the angular distribution parameter of the N7O4,5O4,51D2 Auger line.

Auger spectra were measured using different pieces of the same specimen of Au, Fe, Ni, Al and their oxides by eight participating laboratories. The following points were found: by adjusting the specimen position with respect to the cylindrical mirror analyser using the elastic peak. Auger peak energy values obtained with each instrument were almost identical; Auger line shapes varied from instrument to instrument and from one operating condition to another; the variation of intensity ratio of LVV to LMM of Fe, Ni and their oxidized surfaces may be employed to identify chemical states.

We have recently shown that with the commonly available resolution in Auger electron spectroscopy measurements, significant errors can be incurred in the measured Auger line intensities. To overcome this difficulty, a universal relation has been derived theoretically whereby the experimentally measured line intensities can easily be corrected so as to yield good estimates for the true intensities, i.e. those that would have been measured wre the resolution infinitely good

We report experimental P L2,3VV Auger line shapes of as-cleaved GaP(110) and InP(110) surfaces and of the relative Sb p(1 × 1) interfaces along with calculated slab-resolved densities of states (DOS). The joint experimental and theoretical analysis allows us to disentangle the surface-specific P L2,3VV contribution from the total signal of the as-cleaved surfaces.

A joint experimental and theoretical investigation of the PL2, 3 VV spectrum from the InP(110) surface is presented. The aim is to check for the possibility of separately measuring its surface and bulk components. It is shown that non-reactive overlayers, such as Sb in this case, can be successfully exploited to this end. The comparison with computed spectra allows us to finally present the measured surface component of the PL2, 3 VV spectrum from InP(110).

Auger Line Shape Analysis from solids with open bands has been made considerable progress in recent years. Calculations on Graphite and Pd were encouraging, and new developements in the formalism look promising. However, it must be recognized that the current theory remains much more phenomenological and less predictive and reliable than it is for closed bands. In some sense, the comparison with experiments is more succcesful than our real understanding deserves. This is hardly surprising, in view of the much more fundamental character of the problems involved. An attempt will be made to assess the present state of the theory and foreshadow the directions of future research.

The extended fine structure observed above the NiM 23 VV Auger line of a clean Ni(110) surface was compared with the extended energy loss fine structure related to the NiM 23 -loss absorption edge. There exists a one-to-one correspondence between these two features. The measurements were also performed on oxygen-covered surfaces, with up to 200 L oxygen exposure. The whole set of spectra was interpreted in terms of radial distribution functions. The oxygen-induced variation of the nearest neighbour Ni-Ni distance with respect to the clean surface was related to chemisorption phases developing with oxygen uptake.

This paper reports the existence of a surface miscibility gap in a Cu-0.3at%Ag alloy. Equilibrium surface composition measurements at temperatures in the range 425–580° C have demonstrated that a surface phase transition associated with this miscibility gap results in an abrupt change from a copper-rich to a silver-rich surface (or vice versa) in the vicinity of 500° C. The progress of the transition has also been followed by Auger line scans performed with a high-resolution probe. These have clearly shown the formation and growth of silver-rich patches in a copper-rich surface, and vice versa, in the vicinity of the transition temperature.

Pt0.19Cu0.81 alloy scraped in situ was bombarded by energetic (0.2–2 keV) argon ions and the surface compositions under steady-state bombardment were determined with different energy Auger line combinations. It is found that the outermost surface is enriched in Cu, but that its concentration rapidly decreases to a minimum at the second layer then increases slowly to the bulk value. This fact strongly suggests the existence of a bombardment-induced Gibbsian segregation even at room temperature.

We have used the extend fine-Auger-structure (EXFAS) technique to determine the short-range order of small chromium aggregates deposited in ultrahigh vacuum conditions on polycrystalline graphite. The interpretation of these extended features for structural studies follows very closely that of the extended X-ray absorption fine-structure spectroscopy. The high surface structural sensitivity of this technique is due to the low kinetic energy of the emitted electrons. The EXFAS features above the CrM2,3VV Auger line have been analysed for different deposits of clean chromium clusters. We found a progressive contraction of the interatomic distance, with respect to the bulk, upon reducing the cluster size. This contraction amounts to about 10%.

An experimental evidence is reported on the observation of the Doppler effect in fluorine K-Auger line emitted from a core-ionized SF6 molecule under an impact of 16 keV electrons. The emitting source of the Auger line is found to acquire a kinetic energy of 4.7+/-0.3 keV. We propose that such large energy is released from the Coulomb repulsion taking place between F+ and SF5+ fragment ions under influence of an intense focusing field of the incident electrons. In the presence of the Coulomb field of these ions, the Auger line obtains a polarization P = 76%+/-7%.

Electron‐electron coincidence techniques have been widely used to study atoms and molecules. In contrast, the application of APECS to solids has been much more limited. Recently, however, APECS has started to progress from a technique that is primarily devoted to analyzing Auger line shapes and making interesting anecdotal observations, to an important tool that compliments other analytic techniques for the characterization of solids and their surfaces. In this contribution I will briefly review the status of the field and offer some suggestions for possible scientific opportunities and technological advances.

Ejected electrons from the decay of metastable ${2p}^{5}3s3p{}^{4}{D}_{7/2}$ autoionizing states of Na-like ${\mathrm{Ar}}^{7+}, {\mathrm{Cl}}^{6+},$ and ${\mathrm{S}}^{5+}$ have been detected using an ion-beam delayed-coincidence technique. The previously calculated and measured ${\mathrm{Ar}}^{7+}$ Auger line at $114.10\ifmmode\pm\else\textpm\fi{}0.33 \mathrm{eV}$ was used to calibrate a high-efficiency two-stage parallel-plate electron spectrometer. The energies of the corresponding Auger lines from decay of metastable ${\mathrm{Cl}}^{6+}$ and ${\mathrm{S}}^{5+}$ were subsequently determined to be $102.0\ifmmode\pm\else\textpm\fi{}1.2 \mathrm{eV}$ and $86.6\ifmmode\pm\else\textpm\fi{}1.0 \mathrm{eV},$ respectively. The results are consistent with published data for other members of the Na isoelectronic sequence, and they together exhibit a quadratic scaling with ionic charge q over the range $4l~ql~15.$

Quantitative analysis of the oxidation of Tb was studied by Auger electron spectroscopy (AES). A change in TbNVV Auger line shape was observed with oxidation. Quantitative Auger analysis of oxidised Tb was examined by synthesizing TbNVV lines of pure Tb and Tb4O7 with various ratios. Partially oxidized Tb films TbOx, were quantified by X-ray microanalysis (XMA) and were used as reference samples. Above 10 at % oxidized Tb, the calibration curve obtained from the TbNVV line synthesis method showed good agreement with these experimental results. Below 10 at %, curve synthesis based on non-linear least-squares fitting showed better agreement. Thus, it has been shown that Tb oxidation can be quantitatively analysed by AES with good accuracy.

The oxidation of polycrystalline copper surfaces under oxygen ion bombardment at 80 and 300 K has been investigated with XPS and UPS. The degree of oxidation has been estimated from XPS data involving the relative intensity of the shake-up peak of CuO and the shift of Cu(L 3 VV) Auger line. Copper surfaces were mainly oxidized to Cu 2 O by 0.5, 3 and 10 keV ion bombardment at 300 K. The amount of CuO increased with decreasing ion energy. On the other hand, the sample surface was completely oxidized to CuO with some adsorbates under 0.5 keV oxygen ion bombardment at 80 K. These phenomena indicate that the oxidation by oxygen ion bombardment with lower ion energy is similar to that under higher oxygen potential and that the lowering of the substrate temperature, which gives rise to the lowering of oxidation free energy, causes the increasing degree of oxidation.

By analysis of the coincident impulses in two proportional counters, a study was made of the low-energy photon and electron spectrum (1 kev to 25 kev) emitted simultaneously with beta rays by P/sup 32/. The photon spectrum includes 2.3 kev K-line caused by autoionization of the residual atom, of intensity 5.5 x 10/sup -4/ per disintegration, and the internal bremsstrahlung continuous spectrum; the latter agrees perfectly with the theoretical prediction from 1 kev to 6 kev and then it rises strongly above the theoretical values. The electron spectrum includes the 2 kev Auger line and an important continuous spectrum. The intensity of the latter is higher than predicted by autoionization theory. The discrepancy becomes considerable from 5 kev to 25 kev where 6.6 x 10/sup -3/ associated electrons are found per disintegration. (auth)

We have analyzed refinements in the use of Auger electron spectroscopy to obtain chemical information. We introduce a novel form, the sequential way, of applying the principal component analysis (PCA) and target transformation (TT) methods. In conjunction with a novel form to analyze the experimental error, also based on PCA, we enhance the capability of PCA and TT for extracting the Auger line shape of unknown components. In order to show the capability of this method, we apply it to the study of the palladium crystalline and amorphous silicon interfaces.

We present evidence for two-center interference effects in the autoionization of a Helium atom following a double capture process in a He2+ + H2 collision, by looking, not at the total intensity as in a previous article [1], but at the full width at half maximum of the energy distribution at a function of the observation angle.

We have measured the Ti+ and O- secondary ion emission yields of a Ti sample exposed to oxygen. The oxygen amount at the surface was determined by measuring the OKLL Auger signal, and the chemical effect of oxygen at the surface by measuring the TiLMV and TiLMM Auger line shapes. We found that the oxidation process of Ti presents two clearly differentiated regimes characterized by a different electronic transfer mechanism from titanium to oxygen. These two regimes are also observed in the behavior of the Ti+ and O- yields showing a correlation between the ionization mechanism and the chemical surrounding of the ejected atom.

A simple atomic four-level model is used to explain the changes in the Auger line shape of carbon spectra in different hybridization states. The model is also applicable to other first-row atoms.

Multilayer structures consisting of YBaCuO, Al2O3 and CuO have been sputtered on various substrates. Resistivity measurements show almost no deterioration of the electrical properties of a superconducting YBaCuO film, on top of which first an A12O3 and then an YBaCuO film has been sputtered. First results of YBaCuO films deposited on the A12O3 barrier show a Tcof 65 K.

Pulsed laser evaporation of graphite targets in an ultra high vacuum environment has been utilized to deposit ultra thin carbon films on Si(100) substrates. Analysis of the fine structure of the carbon Auger line reveals significant sp 3 bonding. STM images show that the films are crystalline and that the surface lattice is hexagonal.

An investigation of the fractured surfaces of pins, having a diameter of 1.5 mm, obtained during the production of commercial nodular cast irons of Meehanite types is reported. The investigation was performed using a scanning electron microscope, with a Kevex system for energy dispersive analysis and scanning Auger microprobe, where the principal attention was given to SAM, Point analysis, Auger images and Auger line scans were performed on the fractured surfaces and also approx. 200 A and 1 μ under the surface. The nodule/metal and intercrystalline interfaces in the investigated iron were free of foreign elements.

The composition of deep-buried conductive layers formed by 6 MeV high dose Ni implantation into silicon at 450 K has been studied using AES and SIMS. For a dose of 1.3 × 1018 Ni/cm2, AES analysis yields a Ni to Si ratio close to NiSi2 stoichiometry at profile maximum, as expected from high dose Monte Carlo simulations. In this region the shape of the Si LVV Auger line indicates the presence of NiSi2. TEM/XTEM investigations reveal a continuous NiSi2 layer, showing a high density of extended defects.