Solid-state shifts in the L3M4,5M4,5 Auger spectra of the elements Cu TO Se

The kinetic-energy shifts between atomic and solid-state L₃M_4,5M_4,5 Auger electron spectra of Cu, Zn, Ga, Ge, As, and Se are determined with the aid of semiempirically calculated atomic and experimental solid-state Auger energies. The shift values are calculated by applying the thermochemical model to the Auger process. Good agreement is found between the calculated and experimental values.     

Study of L2,3M4,5M4,5 Auger spectra of Zn and Cu in molecular ZnCl2 and (CuCl)3 vapours

L_2,3M_4,5M_4,5 Auger electron spectra of Zn and Cu have been measured in molecular ZnCl₂ and (CuCl) ₃ vapours. The spectra have been analyzed and compared with the corresponding free-atom spectra. It is found that the main features of the spectra are atomic-like. The energies are shifted by 0.55 eV in ZnCl₂ and by 3.2 eV in (CuCl)₃ towards higher kinetic energy compared with the corresponding free-atom spectra. For the intensity ratios between the L₃ and L₂ groups, the values 2.8 and 3.7 are obtained for Zn and Cu, respectively. These intensity ratio, together with energy considerations based on free-atom Dirac—Fock calculations and observed Auger shifts, indicate that the L₂L₃M_4,5 Coster—Kronig process is energetically possible in (CuCl)₃ molecular clusters but not in ZnCl₂. The satellite structure in the spectra studied also supports this conclusion.     

M4,5N4,5N4,5 auger electron spectrum of Ba metal

The Al Kα excited M_4,5N_4,5N_4,5 Auger spectrum of Ba has been measured from the metallic sample evaporated on a Ag substrate. The spectrum has been decomposed into individual line components after the background subtraction. The decomposed spectrum has been compared with the theoretical spectrum calculated for the 4d^?2 final state configuration in the mixed coupling scheme applying jj-coupling for the initial state and intermediate coupling for the final state. The most prominent structure of the spectrum shows the two 4d-hole coupling, but the structure which is caused by the Auger transitions M_,45N_2,3V has also been observed. The screening of the core holes in Ba metal seems to be produced by (5d6s) electrons. The simple excited atom model HF-calculations give an Auger kinetic energy shift (metal-free atom) of 16.7 eV, which is comparable to the experimental value 14–18 eV.     

On the intensity ratio I(KL2,3L2,3)/I(KL1L1) of the auger carbon lines in series of d-metal carbides

C KVV Auger spectra have been obtained for series of nd-metal carbides (n = 3,4 and 5). The numbers of electrons participating in the C KVV Auger processes for these compounds are estimated by considering the intensity ratio I(KL_2,3L_2,3)/I(KL₁L₁). It is concluded that to explain the high intensities of the KL_2,3L_2,3 Auger lines for the d-metal carbides, it is necessary to consider the participation of conduction-band electrons (and/or interatomic transitions) in the C KVV Auger decay process.     

The L1L2,3V Auger transition in Si

The L₁L_2,3V Auger transition in silicon has been analyzed. No substantial differences are observed in the comparison with the deconvolution of the L_2,3VV Auger spectrum. Comparison is also made with other valence band spectroscopies. It is concluded that L₁L_2,3V transition has a band character.     

Intensity ratios of the KL1L1, KL23L23 oxygen Auger lines in different compounds

A simple model is proposed to interpret the relative intensities of the KLL oxygen Auger lines of several compounds. The basic assumption is that the intensity ratios depend on the atomic charges of the L₁ and L₂₃ orbitals localized at the oxygen site. The appropriate atomic charges can be calculated after Pauling's scale of electronegativity. The theoretical intensity ratios are compared with experimental results of different authors.     

Electronic structure of Ti metal and TiO2 powder studied by hard and soft (Cu Kα1 and Al Kα1) X-ray photoelectron and Auger spectroscopy

High-energy X-ray photoelectron spectroscopy (XPS) is of particular importance for minimizing the effects of surface contamination by increasing photoelectron escape depths. In this study high-resolution high-energy Cu Kα₁ and soft Al Kα₁ XPS and Auger electron spectroscopy were used to compare the electronic structure of Ti in TiO₂ powder and Ti metal. The Ti 1s in TiO₂ XPS line is narrower and more symmetric than in Ti metal. A comparison of the relative intensities of the L₂₃M₂₃M₄₅ and L₂₃M₂₃M₂₃ Auger transitions in Ti metal and TiO₂ is consistent with the expected transfer of Ti 3d electrons away from the Ti site in the oxide. The satellites accompanying the Ti 1s XPS line excited by Cu Kα₁ X-rays occur at the same energies as the satellites accompanying the Ti 2s and 2p XPS lines excited by Al Kα₁ X-rays indicating that they do not depend on the core-level, the experimental resolution or inelastic scattering processes.     

Two hole spectra and valence states in chromium and chromium silicides

Auger spectra for L₃M₂₃V and L₃V V transitions involving, respectively, one and two valence holes in the final state, have been measured for Cr and CrSi₂ using both X-ray photons and electrons as ionization source. Careful subtraction of the energy losses from the raw data permits determination of the lineshape of the Auger spectra. The valence hole spectral functions derived from the L₃M₂₃V transitions are compared with valence band spectra obtained by X-ray photoemission. The comparison provides direct evidence of the importance of multiplet coupling between the 3p and 3d holes in the final state. Results for the spectral function of two valence holes are consistent with the outcome of band structure calculations, although some correlation effects seem to be present.     

Auger electron spectroscopic measurements of ZnCl2-coal interaction

Two anolomous peaks in the ZnL₃M₂,₃M_4,5 Auger electron spectra of dried and heated samples of ZnCl₂-coal mixtures have been interpreted as indication of a Zn-coal bond formation. The peaks show a decrease from the normal 9.1 eV splitting for ZnCl₂ alone to 4.2 eV for ZnCl₂-coal mixtures. High volatile bituminous coals show this effect to a greater extent than either higher or lower rank coals. It is surmised that the side of this bond formation could coincide with the site of catalytic activity in the catalytic hydrogenation of coal in the presence of ZnCl₂.     

Auger and electron energy loss spectroscopic study of surfaces of iron-sulfur alloy,Fe7S8 and FeS2 cleaved in ultra high vacuum

The surfaces of an iron-210 at. ppm sulfur alloy, Fe₇S₈ and FeS₂ cleaved in an ultra high vacuum were studied by Auger (AES) and electron energy loss Spectroscopy (EELS). The S LVV Auger transition for the intergranular fracture plane of the alloy indicates that the sulfur is bonded to the surface as though it were adsorbed. The loss energies of the transition from valence to conduction bands for the surface are identical to those for the transgranular fracture planes. The trans- and intergranular fracture planes have very similar fine structure in the Fe MVV Auger transition profile. This indicates that the interaction between iron and sulfur is too weak to perturb the electronic structure at the fracture surface. The spectral features of the electron transitions having kinetic energies between approximately 40 and 50 eV are explained by a normal Fe MVV Auger transition and an autoionization process after excitation of Fe 3p electrons. The low spin ferrous ion in FeS₂ results in triplet peaks for the Fe MVV transition and doublet peaks for the autoionization event, but similar transitions for Fe₇S₈ exhibit singlet peak for each process.     

Surface oxidation study of Fe67Co18B14Si1 metallic glass using Auger electron spectroscopy

Surface composition and depth profile of native oxide on Fe₆₇Co₁₈B₁₄Si₁ metallic glass has been investigated using Auger electron spectroscopy. The native oxide is compared with chemisorbed oxygen on the cleaned surface. Results indicate that boron segregates on the surface in the presence of oxygen. The low energy L₂₃M₄₅M₄₅ peak of iron in metallic glass is compared with that in crystallized sample and pure iron foil.     

Impurity induced resonance states at the superconducting interface LaAlO3/SrTiO3

Motivated by the recent discovery of superconductivity on the heterointerface LaAlO₃/SrTiO₃, we theoretically investigate the impurity-induced resonance states with coexisting spin singlet s- and triplet p-wave pairing symmetries by considering the influence of Rashba-type spin-orbit interaction (RSOI). Due to the nodal structure of the mixed gap function, we find single nonmagnetic impurity-induced resonance peaks appearing in the local density of state. We also analyze the evolutions of density of states and local density of states with the weight of triplet pairing component determined by the strength of RSOI, which will be widely observed in thin films of superconductors with surface or interface-induced RSOI, or various noncentrosymmetric superconductors in terms of point contact tunneling and scanning tunneling microscopy, and thus shed light on the admixture of the spin singlet and RSOI-induced triplet superconducting states.     

Many-electron effect in the angle resolved L3-M23M23 Auger-photoelectron coincidence spectroscopy (APECS) spectrum of metallic Zn

The many-body effect in the L₃-M₂₃M₂₃ Auger-electron spectroscopy (AES) spectrum of metallic Zn is discussed. The lifetime width and residual relaxation energy shift of the two M₂₃-hole state are governed by the (super) Coster-Kronig (sCK) transitions of two M₂₃-hole state. The residual relaxation energy shift and decay width of the two M₂₃-hole state are calculated in an average configuration by an ab initio atomic many-body theory. The agreement with experiment is good. To elucidate the many-body effect in the two-hole states, it is necessary to be able to discriminate individual components of the multiplet-split AES spectrum. We discuss how to discriminate individual components of the multiplet-split L₃-M₂₃M₂₃ AES spectrum of metallic Zn by angle-resolved Auger-photoelectron coincidence spectroscopy (AR-APECS) in order to determine accurately their line shapes, multiplet splitting energies, and spin states (singlet etc.).     

The M4,5- VV Auger spectrum of silver: An interpretation based on quasi-atomic final states

The M_4,5- VV Auger spectrum of silver has been studied under high-resolution conditions. The relative energies and intensifies of the Auger lines calculated for a 4 d⁸ final state configuration account well for the experimental spectrum. This quasi-atomic behaviour is due to the fact that the effective two-hole Coulomb interaction is larger than the bandwidth. The influence of the solid state on the width of the Auger lines is discussed.     

Vapour phase M4,5N4,5N4,5 Auger electron spectra of antimony and tellurium

High resolution M_4,5N_4,5N_4,5 Auger electron spectra from Sb₄ and Te₂ vapours have been measured using electron impact excitation. The spectra have been decomposed into line components and relative intensities and energies of the components are compared with calculated intensities and energies. The calculations have been done for these molecular samples using the free-atom calculation model involving initially filled shells. The calculations have been treated in the mixed coupling scheme using jj coupling for initial state and intermediate coupling for the final state. The experimental results agree well with the calculated values, indicating that the molecular effects on the relative intensities and energies are very small for these core level transitions. The clear molecular effects are found in the broadening of lines and in the kinetic energy shifts due to extra-atomic relaxation effects.     

Interpretation of Auger satellites in Co,Ni, and Cu compounds

X-ray photoelectron spectra of the 2p levels of Co, Ni, and Cu compounds are examined concurrently with their L₃M_4,5M_4,5 Auger spectra. A correlation is established between the presence or absence of Auger satellites with the presence or absence of photoelectron shake-up satellites for Co and Ni compounds. The correlation is less clear for cupric compounds. We propose the mechanism of Auger shake-up as a plausible interpretation for the observed behavior of these Auger satellites.     

Electronic band structure of TiCl3

Energy bands for the 3d? electrons of Ti³⁺ in the high temperature structure of TiCl₃ have been calculated by the tight-binding approximation. Cubic symmetry around each Ti³⁺ is assumed and transfer between the 3p atomic orbitals of Cl^? and 3d? atomic orbitals of Ti³⁺ is considered. Two singlet bands and two doublet bands with no dispersion have been obtained. The dispersionless character is discussed by constructing Wannier functions.     

ESCA studies of Cu,Cu2O and CuO

Cu 2p, Cu 3d and O 1s electron spectra and Cu L₃M_4,5M_4,5 Auger electron spectra from Cu, Cu₂O and CuO have been studied at 25°C and at 400°C. The height of the Cu 2p satellite peaks from copper oxides was lowered when the temperature was raised. The intensity of the satellites also decreased if the sample stayed in vacuum for prolonged periods.Two commercial cuprous oxides were different with respect to the behaviour of the satellite peaks. One produced very weak satellites, while the other produced strong ones as previously reported in the literature for cuprous oxide. The colour of the oxides was slightly different, indicating that the stoichiometry was not the same.The change in satellite intensity is accompanied by changes in oxygen spectra, Cu L₃M_4,5 M_4,5 Auger spectra and valence band spectra.It is useful to study Auger electrons in addition to the direct electron spectrum, since Auger signals can be more sensitive to surface conditions than direct electron spectra.     

Distribution d'énergie des électrons secondaires émis par InP et GaP soumis à un bombardement d'ions Ar de 40 keV

The energy distributions N(E) of secondary electrons emitted from GaP and InP samples bombarded with 40 keV Ar⁺ ions have been studied by a retarding potential method and an electronic derivation. The spectra show beyond an intensive peak developed at 2 eV, a detailed spectrum between 80 and 140 eV. The analysis of this spectrum reveales Auger electrons corresponding to L₂₃(P) VV and L₂₃M_IV–V(Ga) V [or L₂₃(P) N_IV-V(In) V] transitions; moreover, peaks due to plasmon excitations and d band excitations can be distinguished.     

Esca studies of Ga,As, GaAs,Ga2O3, As2O3 and As2O5

The binding energies of Ga 3d, As 3d, Ga L₃M₄,₅M₄,₅ and O 1s in Ga, As, GaAs, Ga₂O₃, As₂O₃ and As₂O₅ are reevaluated by means of ESCA. The calibration lines of the C 1s and the Au 4f_{$\text{7}\text{2}$} gave different binding energies for the compound materials. In order to determine the absolute binding energies, the chemical shifts in Auger and photoelectron lines from a layered structure composed of thin layer oxide and substrate of a defined material were used. An energy calibration curve, E(Ga 3d) vs. ΔE(GA LMM - Ga 3d), was found to be useful for determination of binding energies in the material which contains gallium. In the case of the GaAs sample, both the chemical etching and the ion bombardment effects on the chemical structure of the GaAs surface are also discussed.