KLL Auger Electron Spectra Research Articles

The experimental investigation of weak effects in the KLL Auger electron spectrum of Zr and Nb generated in radioactive decay

The KLL Auger electron spectra of Zr (Z = 40) and Nb (Z = 41) following respectively the electron capture (EC) decay of 90Nb and the de-excitation of the isomeric state of 91mNb were investigated in detail using a combined electrostatic electron spectrometer and radioactive sources prepared by surface sorption on a polycrystalline carbon substrate. For both elements, energies, relative intensities, and natural widths of all the nine well-resolved basic spectrum components were determined and compared with theoretical predictions and with results of previous measurement as well. Results of our ab initio multiconfiguration Dirac-Hartree-Fock calculations are discussed also in relation to the solid-state effect. Indications of an influence of the EC decay on the absolute energy of the KL2L3(1D2) transition (so-called atomic structure effect) in Zr were found. The effect of the retarded current-current interaction on the KL1L2(3P0) transition intensity was observed to be appreciable for the investigated elements in accordance with the prediction.

Radiative and Auger transitions of core-excited states for the boron isoelectronic sequence

Energy levels, radiative rates, Auger branching ratios of the 1s vacancy resonances 1s2s 22p 2 and 1s2s2p 3 2,4L (L = S, P, D) of the boron isoelectronic sequence including O3+, Ne5+, Mg7+, Si9+ ions are calculated by the saddle-point variation and saddle-point complex-rotation methods. Large-scale wavefunctions are used to obtain reliable results. Relativistic corrections and mass polarisation effects are taken into account to get precise energy levels. Calculated X-ray wavelengths, radiative rates, Auger electron energies, and Auger rates for these core-excited states are compared with available theoretical and experimental results. Furthermore, calculated reliable X-ray wavelengths are used to give possible identifications for satellite lines in the X-ray spectrum of foil-excited magnesium and silicon ions. Calculated Auger electron energies and Auger branching ratios are used to identify oxygen and neon Auger electron spectral lines in previous collision experiments. Three unidentified experimental spectral lines in neon KLL Auger electron spectrum are identified in the present work. The total radiative rates and the total Auger rates for the 1s2s 22p 2 and 1s2s2p 3 resonances of B-like ions are also discussed, as a function of atomic number Z. It is found that the total Auger rates of these resonances are several orders of magnitude larger than the total radiative rates for these low-Z (Z = 6–14) ions.

KLL Auger decay of atomic silicon

The KLL Auger electron spectrum of free silicon atoms has been recorded using electron impact ionization. Besides normal KLL Auger lines, the spectrum shows a rich satellite structure. The KLL Auger transitions following a shake-off or a shake-up of the outermost electron during the K ionization are found to create the strongest satellite spectra. The satellite intensities relative to the total normal KLL Auger intensity were determined semiempirically. The spectral structures have been identified using Hartree–Fock calculations obtained with Cowan's code.

High resolution KLL Auger spectra of free sodium and magnesium atoms

The KLL Auger electron spectra of atomic sodium and magnesium have been recorded with high resolution applying electron impact. Nearly all spectral features have been identified with the help of Hartree–Fock calculations. A comparison of the behaviour of shake probabilities and KLL Auger linewidths for elements with Z = 10 − 13 has been carried out.

The KLL Auger spectrum of 65Cu measured from the EC decay of 65Zn

The KLL Auger electron spectrum of 65Cu following the EC decay of 65Zn has been analyzed at the instrumental resolution of 4.5 and 7 eV using a combined electrostatic spectrometer. Energies and relative intensities of the all nine spectrum components were determined and compared with data obtained from X-ray induced spectra for metallic copper and with results of theories as well. Our value of 7041.8(1.3) eV measured for the absolute energy of the dominant KL 2L 3( 1D 2) spectrum line was found to be higher by 4 eV than those ones obtained in experiments with the use of X-ray photon excitation and by 11 eV (8 σ) than a prediction of the semi-empirical calculations by Larkins. This discrepancy indicates an influence of the “atomic structure effect” on absolute energies of the KLL Auger transitions in 65Cu. Its value was estimated to be from 8 to 15 eV. Good agreement of the measured value of 0.08(2) and that one of 0.066 predicted by relativistic calculation for the KL 1L 2( 3P 0/ 1P 1) transition intensity ratio indicates appreciable influence of the relativistic effects on the KLL Auger spectrum even for copper ( Z = 29).

Atomic electron energy spectra of slow He2+ ions impinging on metallic surfaces

Changes in the KLL Auger electron spectra of slow He2+ ions impinging on surfaces have been proposed as diagnostics of local spin polarization at ferromagnetic surfaces. For a variety of targets Gd(0001), Ni(110), Fe(110) and Al(110) and different ion energies (20–1000eV) and angles of incidence (5–75°) the KLL spectra have been studied. The line ratios depend on the scattering conditions and on the target used, which may give access to the exact behavior of the electronic states in the vicinity of the surface. Additional information on the ion neutralization processes may be available from the angular distributions of the emitted electrons.

Preparation of Au-Pt Nanostructures on Highly Oriented Pyrolytic Graphite Surfaces by Pulsed Laser Deposition and Their Characterization by XPS and AFM Methods

Au-Pt nanostructures on highly oriented pyrolytic graphite (HOPG) were prepared by irradiating bimetallic target under ultrahigh vacuum with pulsed radiation of Nd:YAG laser. The deposited nanostructures were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The measured spectra of Au (4f) and Pt (4f) photoelectrons of laser deposits were composed of two overlapping doublets. Analysis of images obtained from AFM revealed bimodal particle size distribution and presence of few large particles. In agreement with AFM images of the deposit we attributed a two doublet structure of Au (4f) and Pt (4f) spectra to bimodal nanoparticle size distribution. Carbon KLL Auger electron spectra revealed formation of defects in the superficial layers of HOPG by impinging metal ions accompanied by appearance of sp3 hybridized carbon atoms. The dependence of Au (4f) and Pt (4f) core level binding energies on the amount of metals deposited and formation of bimetallic nanoparticles are discussed.

Effects of relativity and “atomic structure” in the KLL Auger spectrum of 88Sr generated in the EC-decay of 88Y

The KLL Auger electron spectrum of 88Sr generated in the EC-decay of 88Y has been analyzed at the instrumental resolution of 11 eV using a combined electrostatic spectrometer. Energies and relative intensities of the all nine transitions were determined and compared with theoretical predictions. Our value of 12067.3(12) eV measured for the absolute energy of the dominant KL 2L 3( 1D 2) transition was found to be higher by 7.4 eV (i.e., more than 3 σ) than that one obtained in a measurement with external excitation. The discrepancy indicates substantial influence of the “atomic structure effect” on absolute transition energies in our experiment. Very good agreement of the measured 0.14(3) and predicted 0.12 values for the KL 1L 2( 3P 0/ 1P 1) Auger transition intensity ratio clearly proved the predicted strong influence of the relativistic effects on the KL 1L 2( 3P 0) transition rate even at Z = 38.

Discrimination between γ′‐Fe4N and ε‐Fe2–3N iron nitride compounds using PCA of Auger electron spectra

AbstractAES offers high spatial resolution that is useful when analysing cross sections of nitrided steels. To discriminate between different iron nitride compounds in such an analysis, so‐called factor analysis (FA) can be applied. This requires acquisition of Auger electron spectra which are associated with either the γ′‐Fe4N or the ε‐Fe2–3N phases as principal components. In this study, the N KLL and Fe LMM Auger electron spectral lines of γ′‐Fe4N and ε‐Fe2–3N phases were acquired in great detail from the pure γ′‐Fe4N and ε‐Fe2–3N phases obtained by gaseous nitriding of pure iron. To this end, two different samples of known composition were analysed. Firstly, Auger electron spectra were recorded from a nitrided layer with large γ′‐Fe4N grains (∼30 µm) on top of an iron substrate. Secondly, Auger electron spectra were recorded from an ε‐Fe2–3N outer layer (∼6 µm) with 26 at.% N, on a γ′‐Fe4N layer (∼4 µm) with 20 at.% N, created on top of an iron substrate. The latter sample was also used for FA. It is shown that principal component analysis of a series of N KLL Auger electron spectra recorded from the iron nitride double layer could be represented by three contributions. These principal components are associated with γ′‐Fe4N, ε‐Fe2–3N and the background. On the other hand, when a background subtraction was applied to the acquired N KLL Auger electron spectra, it was not possible to discriminate between the two iron nitride phases. Copyright © 2006 John Wiley & Sons, Ltd.

Amorphous Boron Carbide by AES

The Auger electron spectra for amorphous boron carbide (B4C) are presented. The first derivative C KLL Auger electron spectrum of a crystalline carbide exhibits a peak shape different from that of adventitious hydrocarbon. The peak shape of the C KLL spectrum for a carbide such as TaC contains three components present at the approximate kinetic energies of 250, 260, and 270 eV, with the peak at 270 eV having a greater intensity in the positive direction than the C KLL spectrum for adventitious hydrocarbon. The features exhibited in the differentiated C KLL Auger spectrum for amorphous B4C are similar, but not identical to other metal carbides and are characteristically different from adventitious hydrocarbon, graphite, SiC, and other metal carbides.

Sputter-etched Silicon Carbide by AES

The Auger electron spectra for sputter-etched silicon carbide are presented. The first derivative C KLL Auger electron spectrum of a crystalline carbide exhibits a peak shape different from that of adventitious hydrocarbon. The peak shape of the C KLL spectrum for a carbide such as TaC contains three components present at the approximate kinetic energies of 250, 260, and 270 eV, with the peak at 270 eV having a greater intensity in the positive direction than the C KLL spectrum for adventitious hydrocarbon. The shape of the differentiated C KLL Auger peak for sputtered SiC exhibits its own unique shape and is characteristically different from adventitious hydrocarbon, graphite, and the other metal carbides.

Auger oxygen KLL lineshapes in silicon oxides: pattern recognition analysis

The pattern recognition method was applied to the oxygen KLL Auger electron spectra of in situ prepared SiO, SiO 2 as standards and native silicon oxides grown on Si(111), SiO and silicon nitride films exposed to air. This method of data evaluation enables us to recognize the chemical state of oxygen from the shape of the O KLL spectra recorded for standards and real silicon oxides surfaces. Results show that the O KLL lineshape recorded for the as-grown and annealed native oxides on Si(111) is nearly the same as for the SiO standard. For the remaining real silicon oxide surfaces the oxygen bonding is more complex with a certain similarity between the O KLL spectra and the corresponding spectra of SiO 2. Recognized changes in the O KLL lineshapes cannot be explained within a mixture model, but by a random bonding model or by a model which assumes that SiO has a unique structure.

Subshell-dependent relaxation in the Auger effect.

The effect of relaxation on KLL, LMM, and MNN Auger-electron spectra of Ne, Mg, Ar, Ca, Zn, and Kr has been studied by the Dirac-Fock method. The relaxation is shown to depend universally on the Auger-electron energy and on the number of peel electrons (${\mathit{N}}_{\mathit{r}}$) in subshells above the final-state holes. In the sudden-approximation limit (large ${\mathit{N}}_{\mathit{r}}$), the relaxation saturates to 14% reduction of the Auger rates in analogy to the 20% reduction of deep inner-shell Dirac-Fock photoionization cross sections well above threshold. The isotropy of the relaxation is emphasized by its small influence on the angular distribution of Auger electrons.

Iron Carbide Formed by Reacting Surface Hydrocarbons with an Iron Film

A first derivative C KLL Auger electron spectrum from an Fe film which was heated to react with adventitious surface hydrocarbons is presented as a “finger print” for the identification of an iron–carbon reaction. The iron carbide peak shape is significantly different from that of the adventitious hydrocarbons prior to heating the sample and a subsequent 1 min argon ion sputter at 1 keV or that of bulk graphite [K. M. Geib, C. W. Wilmsen, J. E. Mahan, and M. C. Bost, J. Appl. Phys. 61, 5299 (1987)]. The carbon is probably bonded as Fe3C because this compound is thermodynamically more stable than the other iron carbides and because the carbon is in an iron rich environment.

Doubly ionized states of N2O studied by photon-induced Auger electron and double charge transfer spectroscopies

The four lowest triplet state energy levels of N 2O2+ have been measured using a modified form of double-charge-transfer spectroscopy. By studying the energetics of the double-electron-capture reactions of 6 keV OH+ ions in collisions with N2O molecules, the lowest triplet state energy levels have been determined to be 36.0+or-0.5, 38.0+or-0.5, 40.9+or-0.5 and 42.0+or-0.5 eV. The singlet state energy levels of the N2O2+ ion have been investigated by means of photon induced Auger electron spectroscopy. The O and N KLL Auger electron spectra have been recorded where the interpretation of the nitrogen spectrum differs greatly from the earlier assignment. Ten distinct structures are observable in the spectra at energies of 37.4+or-0.1, 39.4+or-0.1, 43.1+or-0.1, 43.8+or-0.2, 44.5+or-0.2, 46.7+or-0.2, 47.9+or-0.5, 49.8+or-0.2, 54.0+or-0.5 and 55.4+or-0.2 eV. All structures in both Auger spectra can be assigned in terms of singlet coupled doubly ionized final states. The experimental results have been compared with recent theoretical and experimental data from other laboratories.

Quantitative surface analysis by X-ray photoelectron spectroscopy and X-ray excited auger electron spectroscopy

It is shown that X-ray excited KLL Auger electron spectra allow it to describe measured signal strengths similarly to X-ray photoelectron signals, thus offering valuable information on the quantitative surface composition of a solid sample. The principal equation and corresponding fundamental parameters are discussed. As a result Auger spectra of C, N, O, F, and Na can be easily used in a multiline approach for quantitative analysis. LMM and MNN spectra give rise to more problems, due to their more complicated structure, uncertainties with regard to the background and the influence of Coster-Kronig transitions. These problems are overcome by the use of empirical ratios of the strongest lines of 2p/LMM or 3d/MNN. Since these ratios are independent of sample composition, they allow it to transform the Auger signal into the corresponding photoelectron signal, provided that a standard sample has been measured. Thus a true additional information is obtained and moreover difficulties in cases of photoelectron spectra with overlapping lines from other chemical elements can be overcome.

X‐ray photoelectron and Auger electron spectroscopy studies of photochemical vapor deposition silicon nitrides

Silicon nitride films, deposited by a low‐temperature photochemical vapor deposition method, were characterized by optical, physical, and chemical methods. The film reflectivity was a function of the wavelength of the incident beam and varied from 0.45 to 0.02 in the 4000–7000 Å region. These values changed upon annealing at high temperatures. Film uniformity, in terms of thickness and refractive index, was good over the substrate (±5% and ±0.5%, respectively). The refractive index was 1.95 in the as‐deposited condition and upon annealing exhibited a significant increase due to densification and a decrease in the nonstoichiometric nitride component along with a concurrent increase in the Si3N4 and excess Si amounts. The dramatic decrease in etch rate in buffered HF, from ∼1200 Å/min in the as‐deposited condition to <80 Å/min after annealing at 800 °C, was also consistent with the above observations. The pinhole density in these films also decreased considerably after annealing (from ∼100/cm2 to <15/cm2). X‐ray photoelectron and Auger electron spectroscopy were used to characterize the composition of these films. The composition profiles exhibited good uniformity through the films, with oxygen and carbon contamination limited to within 100 Å from the surface. The Si 2p photoelectron and the Si KLL Auger electron spectra were broad and upon deconvolution indicated the presence of four different silicon containing species. These were identified as SiO2, stoichiometric nitride (Si3N4), nonstoichiometric nitride (SiNx, 0<x≤1), and excess silicon bonded with hydrogen (SiHy, 0<y<2). SiO2 was detected only on the surface, due to exposure to atmosphere. After high‐temperature annealing, the intensities of the nonstoichiometric nitride component in both the Si 2p and the Si KLL spectra decreased and the intensities of the Si3N4 and excess Si peaks increased suggesting partial decomposition of SiNx to Si3N4 and excess Si.

He +-induced auger electron studies in carbon-containing molecules

He +-induced KLL Auger electron spectra of energy resolution 0.3 and 0.6 eV have been measured for incident energies of 0.45 to 2.1 MeV for several simple carbon-containing compounds (CH 4, C 2H 6, C 2H 4, C 2H 2, CO, CO 2, CF 4, and C 2F 6). The indicate that line widths and energies of major lines in the hydrocarbons and in CO induced by He + bombardment do not appear to be different from those produced by e − bombardment. Differences of more than 30% are observed in the measured relative He +-induced Auger yields, and we attempt to reproduce the observed variations in yield by scaling first to an effective carbon valence number and second with the use of electron scattering cross sections. Results of a preliminary analysis of the Auger line structure are reported.

Characterization of Photo-Cvd Silicon Oxide

ABSTRACTA photochemical vapor deposition technique was used to deposit silicon oxide films. A range of film properties was produced through changes in the process conditions. Refractive index, indicative of film composition, varied from 1.5 to 2.0, corresponding to oxygen rich and silicon rich conditions, respectively. Etch rate in buffered HF was a strong function of the refractive index, with higher index of refraction yielding lower rates. Film stress was tensile and the magnitude of the stress was again related to the index of refraction. Other properties that were evaluated included pinhole density and adhesion to Si. All the properties were directly relatable to the basic film composition.X-ray photo electron and Auger electron spectroscopy were used to characterize the composition of these films. The Si 2p photoelectron and the Si KLL Auger electron spectra were broad for higher refractive index films and upon deconvolution indicated the presence of different silicon containing species, the natures of which depended upon the actual index of refraction. For stoichiometric films, the predominant constituent was SiO2 and for non-stoichiometric films, varying amounts of Si2O, SiO, Si2O3 and SiO2 were all present.

Kinetic-energy shifts in vapour-phase auger-electron spectra of sodium halide molecules

The KLL Auger-electron spectrum of sodium and the strongest Auger lines of its halides have been measured from Na, NaF, NaCI, NaBr and NaI in the vapour phase by using electron-impact excitation. The kinetic-energy shifts of the sodium lines in the sodium halides are found to be dominated by molecular relaxation and not by chemical initial-state effects. The chemical shifts have been calculated within the simple point-charge model, and the molecular-relaxation contributions to the shifts have been estimated from differences between semiempirically calculated and measured Auger energies. The molecular-relaxation contribution to the shifts of sodium Auger lines is found to increase strongly on going from NaF to NaI. In contrast, for the halides this relaxation contribution seems to have an almost constant value.