High-resolution Auger Electron Research Articles

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Surface chemical analysis by XPS is more than 60 years old. During the last 15 years ther-e has been an explosive growth in the publication of XPS peak-fits and interpretations. Unfortunately, these publications suffer from a variety of problems in reliability and usefulness because the new authors are not familiar enough with the science and application of XPS, chemical state assignments, and peak-fitting. Efforts to help new users include journal publications such as self-training guides for peak-fitting, international standards, collections of BEs, examples of peak-fitting, and more. These user guides are useful and are published in journals that are known to publish XPS information. The basics of XPS are taught at a few graduate level courses in universities and there are 3–5 day training courses at conferences, but the need is much greater. To help the international XPS community and the infrequent users of XPS to overcome these limitations, problems and needs, The XPS Library™ was formed as a non-profit institute to provide an on-line resource of XPS information, self-training material, free >70,000 monochromatic XPS reference spectra, free spectral data processing software, reference tables, links, examples of good and bad peak-fitting, and more. In 1986, this author began to build The XPS Spectra-Base™ by collecting and organizing detailed sets of “self-consistent” monochromatic XPS spectra from reference materials, natural crystals, man-made single crystals, and commercial products. The current number of individual spectra in digital form is >70,000 and the number of materials is >9,000. Each set of spectra (4–10) is stored inside individual data directories having the name of the material analyzed. Multiple data directories belonging to the same category are placed in a directory with the name of that category. Each category name is distinct and is based on the chemistry of the materials. Currently, “XPS Library” members must download individual sets of spectra or full directories that are stored in ZIP files. To view, peak-fit, export, analyze, overlay, process, or print the spectra provided by The XPS Spectra-Base the library member needs a software that can import or directly open spectra having: VAMAS-ISO 14,976 ASCII file format, other ASCII file formats (XY, XYZ), or the SDP binary file format. Most software from the instrument makers can import these types of spectra. The “Spectral Data Processor” (SDP™) v8.0 is a 32-bit Windows™ (v7−10 compatible) software is provided free of charge to library members. Using SDP v8 the user can: (a) access and open the raw or processed spectra downloaded from The XPS Spectra-Base, (b) save all processing results and labels to permanent memory, (c) completely reprocess, peak-fit, analyze, overlay, process, or print the spectra, (d) export or save the raw or processed spectra in VAMAS-ISO ASCII and other ASCII file formats, and (e) import spectra having VAMAS-ISO 14,976 ASCII file format and other ASCII file formats (XY, XYZ). Several thousand High Energy Resolution Auger Electron Spectra (HER-AES) from insulators, conductors, and native oxides will be added. All spectra are owned, copyrighted, and are the property of The XPS Library and are protected by a registered international copyright (TX 4−560-881).

Conjugate photoelectron recapture peaks in the high resolution Auger electron spectra following near-threshold Ar 2p photoionization

We have observed formation of Rydberg series superimposed on the Ar (L3M2,3M2,3) Auger electron spectral profile with photoexcitation just above the 2p−13/2 photoionization threshold. This is due to the recapture of photoelectrons induced by post-collision interaction between the Auger electron and photoelectron: Ar+ 2p−13/2 + e− → Ar+ 3p−2ml + e−. The intensity distribution of the angular momentum state resolved Rydberg peaks revealed prominent conjugate peaks due to angular momentum exchange between photoelectrons and Auger electrons in the process. In addition, we measured the 2p−13/2nl → 3p−2ml + e− resonant Auger spectra with high resolution below the 2p−13/2 threshold. Our results showed that conjugate shake-up/down 2p−13/2nd → 3p−2mp + e− processes are stronger than the direct 2p−13/2nd → 3p−2ms, (m−1)d + e− processes in the spectator Auger processes, implying a strong angular momentum exchange effect between photoelectron and Auger electron.

Dominance of angular momentum exchange in the PCI recapture of photoelectrons revealed by high resolution Auger electron measurements of Kr

An unexpectedly prominent angular momentum exchange effect in the double photoionization continuum was identified through the photoelectron recapture process induced by post-collision interaction (PCI). The Kr (M5N2,3N2,3) Auger electron spectrum originating from 3d−15/2 photoionization was measured with the photon energy tuned very close above the ionization threshold. As the photon energy approached the 3d−15/2 photoionization threshold, Rydberg series structures including several angular momentum components were formed within the Auger peak profile by the recapture of the photoelectrons into high-lying final ion orbitals. Our spectrum with line-width much narrower than the lifetime width of the corresponding core excited state allowed us to resolve detailed structures due to the orbital angular momentum states very clearly. Unexpectedly, conjugate peaks originating from the exchange of angular momentum between the photoelectron and the Auger electron through PCI were found to dominate the spectrum. Comparison with valence photoelectron spectrum of Kr via direct photoionization confirms the new assignment. Conjugate peaks were also found to be in accord with the quantum defect values obtained for the high Rydberg series Kr+4p−2(1S0, 1D2)ml. Extension of the new assignments to photon energies below threshold may call for the revision of previous interpretations of resonance Auger processes.

Experimental Study of Wear Mechanisms of Cemented Carbide in the Turning of Ti6Al4V.

Titanium and titanium alloys such as Ti-6Al-4V are generally considered as difficult-to-machine materials. This is mainly due to their high chemical reactivity, poor thermal conductivity, and high strength, which is maintained at elevated temperatures. As a result, the cutting tool is exposed to rather extreme contact conditions resulting in plastic deformation and wear. In the present work, the mechanisms behind the crater and flank wear of uncoated cemented carbide inserts in the turning of Ti6Al4V are characterized using high-resolution scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and high-resolution Auger electron spectroscopy (AES).The results show that, for combinations of low cutting speeds and feeds, crater and flank wear were found to be controlled by an attrition wear mechanism, while for combinations of medium to high cutting speeds and feeds, a diffusion wear mechanism was found to control the wear. For the latter combinations, high-resolution SEM and AES analysis reveal the formation of an approximately 100 nm thick carbon-depleted tungsten carbide (WC)-layer at the cemented carbide/Ti6Al4V interface due to the diffusion of carbon into the adhered build-up layers of work material on the rake and flank surfaces.

Wear of a high cBN content PCBN cutting tool during hard milling of powder metallurgy cold work tool steels

The wear characteristics of a high cBN content PCBN cutting tool during hard milling of two different hardened cold work tool steels have been evaluated. Post-cutting examination of the worn cutting inserts was performed using high resolution field emission gun scanning electron microscopy, energy dispersive X-ray spectroscopy, Auger electron spectroscopy and optical surface profilometry. Also, the machined work material surfaces and collected chips were characterized in order to evaluate the prevailing wear mechanisms.The results show that both flank and crater wear are controlled by continuous wear due to tribochemical reactions, adhesive wear and mild abrasive wear. Besides, the cutting inserts show a tendency to micro-chipping along the cutting edge especially at higher cutting speed. The latter mechanism was also found to be dependent on type of work material. High lateral resolution Auger electron spectroscopy of the crater region shows that the worn surface is covered by a thin SixOy rich tribofilm with a thickness of 50–500nm, the tribofilm being thicker on the binder phase regions. Also, the Co-rich regions of the binder phase seem to be more tribochemically affected by the prevailing contact conditions as compared with the W-rich regions of the binder phase and the cBN phase.

4fphotoionization and subsequent Auger decay in atomic Pb: Relativistic effects

High-resolution 4f photoelectron and subsequent Auger-electron spectra have been measured from free Pb atoms using synchrotron radiation. The fine structure of the spectra has been investigated theoretically by calculating the energies and intensities for 4f photoionization and Auger decay processes using the multiconfigurational Dirac-Fock approach. The role of the relativistic effects in the ground and singly and doubly ionized states has been studied on the basis of computed results and their comparison with experiment.

High Lateral Resolution Auger Electron Spectroscopic (AES) Measurements for Sn Whiskers on Brass

We report high lateral resolution Auger electron spectroscopic (AES) measurements on high aspect ratio Sn whiskers. The whiskers were grown from compressively stressed thin films (~ 6000 Å) of Sn on brass using a magnetron sputtering system. The Auger spectra show that, after sputter cleaning, the whisker is nearly 100% Sn at all locations along the whisker shaft, at the growing blunt end of the shaft, and with depth (~ 1000 Å) into the side of the whisker. The “as received” Sn whisker surface shows the expected ~ 200 Å of native Sn oxide at all locations and the O signal nearly disappeared (~ 3 atom%) after 200 Å of sputter cleaning. There was no evidence of high amounts of oxygen within the bulk of the whisker. That brass is not observed in the whisker shaft supports the notion that whisker formation is accompanied by material mass transport through interfaces and grain boundaries which causes stress (usually compressive) relief. This is supported by the most remarkable aspect of the whisker growth; namely, that high aspect ratio Sn whiskers ~ 100-500 μm in length containing no brass can be grown from a ~ 0.6 μm thin film of Sn.

Structural analyses of RuO2–TiO2/Ti and IrO2–RuO2–TiO2/Ti anodes used in industrial chlor-alkali membrane processes

The morphology and composition of RuO2–TiO2/Ti and IrO2–RuO2–TiO2/Ti anodes, which have been used for the production of chlorine for more than 10 years, were analyzed by various methods; such as high-resolution scanning electron microscopy, high-resolution Auger electron spectroscopy, electron probe X-ray emission microanalysis and X-ray diffraction analysis. Drastic changes in the surface morphology, including partial exfoliation of a small amount of the oxide layer and a reduction in the content of ruthenium species through dissolution, were observed for the RuO2–TiO2/Ti anode. For the IrO2–RuO2–TiO2/Ti anode, on the other hand, there were moderate changes in the surface morphology and moderate dissolution of iridium and ruthenium species.

High-resolution Auger-electron spectroscopy induced by positron annihilation on Fe, Ni, Cu, Zn, Pd, and Au

Positron annihilation induced Auger electron spectroscopy (PAES) enables almost background free, non-destructive surface analysis with high surface selectivity. The Auger-spectrometer at the high intense positron source NEPOMUC now allows to record positron annihilation induced Auger spectra within a short data acquisition time of 10-80 minutes. With a new hemispherical electron energy analyzer and due to the exceptional peak to noise ratio, we succeeded to measure Auger-transitions such as the M2,3V V double peak of nickel with high energy resolution. The relative Auger-electron intensities are obtained by the analysis of the recorded positron annihilation induced Auger spectra for the surfaces of Fe, Ni, Cu, Pd and Au. It is demonstrated, that high-resolution PAES allows to determine experimentally the relative surface core annihilation probability of various atomic levels.

Development of an Apparatus for High-Resolution Auger Photoelectron Coincidence Spectroscopy (APECS) and Electron Ion Coincidence (EICO) Spectroscopy

We have developed an electron electron ion coincidence (EEICO) apparatus for high-resolution Auger photoelectron coincidence spectroscopy (APECS) and electron ion coincidence (EICO) spectroscopy. It consists of a coaxially symmetric mirror electron energy analyzer (ASMA), a miniature double-pass cylindrical mirror electron energy analyzer (DP-CMA), a miniature time-of-flight ion mass spectrometer (TOF-MS), a magnetic shield, an xyz stage, a tilt-adjustment mechanism, and a conflat flange with an outer diameter of 203 mm. A sample surface was irradiated by synchrotron radiation, and emitted electrons were energy-analyzed and detected by the ASMA and the DP-CMA, while desorbed ions were mass-analyzed and detected by the TOF-MS. The performance of the new EEICO analyzer was evaluated by measuring Si 2p photoelectron spectra of clean Si(001)-2×1 and Si(111)-7×7, and by measuring Si-L23VV-Si-2p Auger photoelectron coincidence spectra (Si-L23VV-Si-2p APECS) of clean Si(001)-2×1.

Annealing Effects on Silicon Oxynitride Layer Synthesized by N Plasma Immersion Ion Implantation

A silicon oxynitride layer was obtained on a polished silicon wafer surface by nitrogen plasma immersion ion implantation. Oxygen is provided by the residual gas in the implantation chamber (base pressure of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3 times 10^-5 hboxmbar$</tex> ) and is also implanted as the main impurity. As-implanted Si samples were analyzed by high-resolution Auger electron spectroscopy (AES), which indicated the formation of a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$hboxSiO_ xhboxN_ y$</tex> layer of about 30 nm with varying <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$x$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$y$</tex> , along the depth of the treatment layer. AES also provided concentration profiles of the implanted elements at the as-implanted stage. Annealing of samples from a batch of such oxynitrided Si samples was carried out at different temperatures ranging from 200 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$^circhboxC$</tex> to 1060 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$^circhboxC$</tex> . The AES analysis of these annealed samples indicated a significant escape of the implanted nitrogen atoms (starting already at 200 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$^circhboxC$</tex> ), but even at 1060 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$^circhboxC$</tex> , there was a very thin (about 12 nm) remaining layer of the silicon oxynitride, which is probably in crystalline form. Results from high-resolution X-ray diffraction measurements also corroborate the aforementioned results.

Activation of Cu-Based Amorphous Alloys Ribbons for Catalytic Applications

Results to develop new and effective procedures to activate Cu- Ti, Cu-Zr, and Cu-Hf amorphous alloy ribbons for catalytic applications are summarized. A wide range of activation methods has been successfully applied to transform Cu-Zr alloys into catalysts of high and stable catalytic activity and selectivity. In contrast, only specific procedures may be used to activate Cu-Ti and Cu-Hf amorphous samples. Various characterization techniques including surface enhanced Raman spectroscopy (SERS), XRD, wavelength/energy dispersive spectrometry (WDS/EDS), scanning electron microscopy (SEM), high-resolution Auger electron microanalysis (SAM), Auger electron spectroscopy (AES), porosity and surface area measurements provide data to interpret changes in structural, surface and catalytic properties.

Photoionization and Auger decay of the3dvacancy state of atomic strontium: Electron-electron correlations

The 3d photoionization and subsequent normal Auger decay processes in atomic strontium have been investigated. To understand the electron spectra following photoionization of a 3d electron, a series of ab initio computations, based on the multiconfiguration Dirac-Fock method, were performed. From the calculated photoionization and Auger decay amplitudes the relative photoionization cross sections were derived, together with the total and partial Auger decay widths and relative Auger intensities. Emphasis was placed on the effects of electron-electron correlations in the 3d hole state. The theoretical predictions were compared to the high-resolution synchrotron radiation-induced photoelectron and Auger electron spectra.

An investigation of Fe 74Si 11B 14Ni 1 soft-magnetic powder

Fe 74Si 11B 14Ni 1 soft-magnetic material was prepared as a powder using water atomisation. Using this method, powder particles of less than 45 μm in diameter were obtained after sieving. In the as-water-atomised condition the powder particles were observed to be amorphous. Annealing resulted in the formation of a two-phase nanostructured morphology. The structure of the powders was investigated by high-resolution Auger electron spectroscopy (HRAES) and field-emission scanning electron microscopy (FE SEM) with WDS analytical technique.

Oxidation of beryllium—a scanning Auger investigation

Beryllium is considered to be a candidate material for the first wall of nuclear fusion plasma experiments, e.g. ITER. In this application, the interaction of beryllium with oxygen is important for two reasons. One aspect is the reaction of hot beryllium with air in case of a catastrophic leak, the other is the action of beryllium as a getter, binding oxygen impurities and thus helping to keep the level of contamination in the plasma low. We therefore investigated the interaction of beryllium with air at elevated temperatures up to 600°C on a microscopic level, using a high resolution Auger electron microscope. At 390°C, a thin protective oxide film is formed, while at 500°C oxidation starts to enter into the grain boundaries, leading to the loosening of small particles of beryllium already at 600°C. The expected diffusion of oxygen from the surface into the bulk has not been observed up to 390°C, the highest temperature to be safely applied inside the Auger microscope. Exposure to hydrogen atmosphere showed no change up to 600°C, exposure to hydrogen plasma resulted in an equilibrium thickness of the oxide layer, which is most likely due to impurities in the plasma. Thus, an operation of beryllium liners as a non-evaporable getter is not to be expected in this temperature range. Getter activity linked to the transport of beryllium from the liner to some deposition areas is, however, possible.

Molecular photodissociation studied by VUV and soft x-ray radiation

A brief account of the developments in photodissociation studies of free molecules by VUV and soft x-ray sources is given as an extended introduction. Then two typical experimental setups are described for multiple-ion coincidence momentum imaging and high-resolution Auger electron–ion coincidence momentum imaging. Finally, some individual cases of molecular dissociation following core-hole creation are examined, to illustrate how the complex multidimensional data produced can be represented and interpreted. The new experimental techniques based on Coulomb explosion are shown to allow direct characterization of the initial nuclear motions which follow electronic excitation.

Electronic energy-density effects in ion tracks of metals

High resolution Auger-electron spectroscopy has been applied to the interaction of swift heavy ions with atomically clean metallic solids. Spectra have been taken for fast projectile electrons and for charge-state equilibrated ions at normal incidence on microcrystalline beryllium samples, Al(100) single crystals and several metallic glasses (Al87La7Ni5Zr1, Ni78B14Si8, Co66Si16B12Fe4Mo2). From the energy shift and from the Auger-line width we have extracted ion-track potentials and also electron temperatures inside ion tracks. A first determination of the angular distribution of multiple-ionization lines is presented as well.

Electron Correlation in the Formation of Hollow States along the Li-like Isoelectronic Sequence

Hollow-state (double K-shell vacancy) production in Li-like Be+, B2+, C3+, and F6+ ions colliding with He has been investigated using high-resolution Auger-electron spectroscopy. The formation of discrete states and their relative intensities show striking dependences on the nuclear charge Z of the ion. From the projectile velocity dependences of these states the contribution of the electron-electron interaction is determined, showing that the hollow states are formed largely by electron correlation with a strength that diminishes for increasing Z.

Characterization of steel mill electric-arc furnace dust

In order to make a complete characterization of electric-arc furnace (EAF) dust, as hazardous industrial waste, and to solve its permanent disposal and/or recovery, bearing in mind both the volumes formed in the Croatian steel industry and experiences of developed industrial countries, a study of its properties was undertaken. For this purpose, samples of EAF dust, taken from the regular production process in the Željezara Sisak Steel Mill between December 2000 and December 2001, were subjected to a series of tests. The chemical composition of EAF dust samples was investigated by means of a several different analytical methods. The results from the chemical analysis show that the approximate order of abundance of major elements in EAF dusts is as follows: Fe, Zn, Mn, Ca, Mg, Si, Pb, S, Cr, Cu, Al, C, Ni, Cd, As and Hg. Granular-metric composition of single samples was determined by applying sieve separation. Scanning electron micro-structural examination of EAF dust microstructure was performed and results indicated that all twelve EAF dusts were composed of solid spherical agglomerates with Fe, Zn, Pb, O, Si and Ca as the principal element. The investigation of grain morphology and the mineralogical composition of EAF dust were taken by combination of high resolution Auger electron spectroscopy (HR AES), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction analysis. The analysis of XPS-spectra determined the presence of zinc in the form of ZnO phase and the presence of lead in the form of PbO phase, i.e. PbSO 3/PbSO 4 forms. The results of the X-ray diffraction phase analysis show that the basis of the examined EAF dust samples is made of a mixture of metal oxides, silicates and sulphates. The metal concentration, anions, pH value and conductivity in water eluates was determined in order to define the influence of EAF dust on the environment.

Strategy for Applying Microanalytical Techniques

A combination of microanalysis techniques is used to reveal with great precision the composition and microstructure of typical features in engineering materials. In this paper small particles, very thin films, interfaces and their contiguous region are considered. Small silicon nitride particles in an iron matrix produced by nitriding are characterized quantitatively with High Resolution Electron Microscopy (HREM) and Electron Probe Micro Analysis (EPMA) using Wavelength Dispersive X-ray Spectrometry (WDS). Thin aluminium-oxide films grown on aluminium substrates by thermal oxidation at low pressure are investigated with HREM and X-ray Photoelectron Spectroscopy (XPS). Their thickness, composition and degree of crystallinity are established as a function of oxidation temperature and time. At and near the oxide-layer/MCrAlY-coating (M=Ni and/or Co) interface the aluminium and chromium depletion behaviour of the coating material due to high-temperature oxidation is studied with high-resolution Scanning Electron Microscopy (SEM), EPMA and Auger electron spectroscopy (AES). The composition-depth profiles obtained for the coating material are used to determine the composition dependent diffusion coefficients. These properties are crucial for the prediction through computational modelling of the coating material oxidation behaviour and enable the development of new coating materials.