Spectres Auger sous bombardement d'ions Ar+ de 60 keV de quelques éléments purs et de composés binaires

Auger spectra of different elements, alloys and compounds excited by 60 keV argon ions have been obtained. These spectra show a detailed structure with, in particular, a sharp Auger peak. This peak is interpreted as a superposition of two kinds of Auger transitions: the first one occurs with two electrons of the electronic band, the second, takes place from electrons situated on “quasi-atomic” outer shells. On the low energy side of Auger line, two equidistant peaks attributed to Auger electrons having suffered energy losses by ionization of electronic outer shell of target-atoms were observed. From Mg, Al, Si, P and S Auger transitions due to initial double L_ii,iii level ionization were detected. The interpretation of the creation of a vacancy in electronic inner shell at the origin of Auger effect by ionic bombardment is given from the electronic promotion model of Fano and Lichten.     

3 to 15 keV Ar+ induced Auger electron emission from Si and Ar

Ar⁺ induced Auger electrons from Si and Ar were investigated at bombardment energies between 3–15 keV and target currents of a few μA. The Auger electron yields were compared with secondary ion yields of Si and Ar by simultaneous SIMS-AES measurements. In the ion induced Auger spectra of Si five Auger peaks and in the Ar spectra three Auger peaks were observed. The ion induced Auger electron yield of Si and Ar were found to be strongly dependent upon the primary ion energy. “Bulk like” and “atomic like” Auger transitions of ion induced Auger electrons of Si were observed.     

Energy and angular distributions of electrons emitted by direct double auger decay

We have observed the direct L(2,3)MMM double Auger transition after photoionization of the 2p shell of argon by angle-resolved electron-electron coincidence spectroscopy. The process is responsible for about 20% of the observed Auger electron intensity. In contrast to the normal Auger lines, the spectra in double Auger decay show a continuous intensity distribution. The energy and angular distributions of the emitted electrons allow one to obtain information on the electron correlations giving rise to the double Auger process as well as the symmetry of the associated two-electron continuum state.     

Binary collision model for neon Auger spectra from neon ion bombardment of the aluminum surface

A model is developed to account for the angle-resolved Auger spectra from neon ion bombardment of the aluminum surface recently obtained by Pepper and Aron. The neon is assumed to be excited in a single asymmetric neon-aluminum collision and scattered back into the vacuum where it emits an Auger electron. The velocity of the Auger electron acquires a Doppler shift by virtue of the emission from a moving source. The dependence of the Auger peak shape and energy on the incident ion energy, angle of incidence and on the angle of Auger electron emission with respect to the surface is presented. Satisfactory agreement with the angle resolved experimental observations is obtained. The dependence of the angle-integrated Auger yield on the incident ion energy and angle of incidence is also obtained and shown to be in satisfactory agreement with available experimental evidence.     

Resonant Auger decay in the L2,3-MM spectrum of Ar excited by electron bombardment

The L_2,3-MM Auger spectrum of argon was measured using electron beam excitation. A weak structure on the high energy side of the main transitions was identified as corresponding to the resonant Auger transitions by comparing these spectral structures with individual resonant Auger spectra excited by monochromatic synchrotron radiation.     

Electron excited Auger line shape study of ion-beam-mixed Pd–Au alloys

The electronic structure of the ion-beam-mixed Pd–Au alloys have been studied using valence band spectra of XPS and electron excited CVV–Auger spectra. To show the relationship between the electronic structure changes and the Auger spectral line shape, the data of the self-convolution of the partially weighted valence band spectra was compared with the Auger spectra of Pd–Au alloys. The Pd–Au alloy is one of the systems which both atomic and band-like contributions are evident in the Auger spectral line shape. Since the self-convolution of PDOS’s relates to the band-like part of Auger spectra, in Pd–Au alloys, the band-like structure in the Auger line shape can be classified by the self-convolution of the partially weighted valence band spectra. Finally, we found that the increase in peak size at ∼80 eV with the increase in Pd content is due to the band-like contribution in the Au N_6,7VV Auger line shape.     

Excitation and decay dynamics of 1s2s inner-shell double-vacancy states of neon atoms

The photo-excitation and Auger decay processes of inner-shell double vacancy states 1s2s2p^6（1,3^S）3s3p of neutral neon atoms have been studied theoretically. Multi-configuration Dirac-Fock （MCDF） calculations have been carried out, with electron correlation effects taken into consideration. The relaxation of core and excited orbitals and configuration interaction are found to be crucial to creating the double vacancy states by single photo-absorption. The predominant decay paths for the double vacancy states turn out to be of the LLM Auger decay to 1s 2s^22p^53s（3p）, KLL Auger decay to 1s^22s2p^43s3p, and KLM Auger decay to 1s^22p^63s（3p）. They lead to further Auger decay, creating the neon ions of multiple charge states. For both double and single vacancy states the spectator type of Auger process is dominated in all the Auger decay processes. Theoretical Anger electron spectra are presented for further investigations, experimental and theoretical.     

PCA-Based Analysis of X-Ray-Excited Auger Spectra from Non-ordered Ag(110)

Principal-components analysis (PCA) followed by factor analysis enables one to decompose the structure of Auger lines originating from large effects such as energy shifts induced by chemical effects. The aim of the present contribution is to show that PCA can also be effectively used for detection of composed structure in a set of Auger spectra even if the observed changes in line shape are very subtle. The analysed set of X-ray-excited MNN Auger spectra from Ag(110) shows a clear correlation between peak shifts and peak widths. This correlation can be explained as a result of the composed structure of the recorded Auger lines. It is suggested that the resultant Auger lines may consist of a number of constituents, each referred to Ag atoms differing in the value of their co-ordination number.     

Microscopic theory of Auger recombination in quantum wires

An analysis is made of mechanisms for Auger recombination of nonequilibrium carriers in cylindrical quantum wires. It is shown that two different Auger recombination mechanisms take place in these wires: a quasi-threshold and a nonthreshold mechanism. Both mechanisms are associated with the presence of heterobarriers but are of a different nature. The quasi-threshold mechanism is attributed to the spatial confinement of the carrier wave functions to the region of the quantum wire and in this case the quasi-momentum conservation law is violated and the Auger recombination process is intensified. As the radius of the wire increases, the quasi-threshold Auger recombination process goes over to a threshold process. The nonthreshold mechanism is caused by the scattering of an electron (hole) at the heterojunction; the rate of this nonthreshold Auger recombination tends to zero in the limit of an infinite-radius wire.     

Multielectron spectroscopy: the xenon 4d hole double auger decay

A magnetic bottle spectrometer of the type recently developed by Eland et al. [Phys. Rev. Lett. 90, 053003 (2003).] has been implemented for use with synchrotron radiation, allowing multidimensional electron spectroscopy. Its application to the Xe 4d double Auger decay reveals all the energy pathways involved. The dominant path is a cascade process with a rapid (6 fs) ejection of a first Auger electron followed by the slower (>23 fs) emission of a second Auger electron. Weaker processes implying 3 electron processes are also revealed, namely, direct double Auger and associated Rydberg series.     

Unveiling residual molecular binding in triply charged hydrogen bromide

We present an experimental and theoretical study of triply charged hydrogen bromide ions formed by photoionization of the inner 3d shell of Br. The experimental results, obtained by detecting the 3d photoelectron in coincidence with the two subsequent Auger electrons, are analyzed using calculated potential energy curves of HBr3+. The competition between the short-range chemical binding potential and the Coulomb repulsion in the dissociative process is shown. Two different mechanisms are observed for double Auger decay: one, a direct process with simultaneous ejection of two Auger electrons to final HBr3+ ionic states and the other, a cascade process involving double Auger decay characterized by the autoionization of Br*+ ion subsequent to the HBr2+ fragmentation.     

Transition rates for interatomic Auger processes

Theoretical estimates in the LCAO approximation reveal that matrix elements for interatomic Auger processes are very strongly energy dependent, but that for very low energy Auger transitions they may be comparable with the competing intra-atomic Auger processes. Though inter-atomic Auger mechanisms will not produce appreciable lifetime broadening, they may radically change the low energy Auger spectrum, for example, of metallic elements in the early stages of oxidation, and may mainly control the transition rates of low energy Auger processes in ionic crystals.     

Distinction between weak Auger transitions and internal X-ray photoemission

Estimates of the relative intensities of KLV Auger electrons and internally excited photoelectrons of similar energy show that the Auger process will dominate contrary to a recent suggestion by Powell.     

Korrelationseffekte in den Auger-Spektren von Edelgasen

The possibility of studying correlation effects through Auger electron spectrometry has been shown recently by Krause, Carlson and Moddeman in the case of theK Auger spectrum of neon. As a further example we have measured theM _4,5 Auger spectrum of krypton with high resolution. Correlation effects have been found via the strong deviations of relative intensities of Auger diagram lines (e.g.M _4,5 N ₁ N _2,3(¹ p ₁)) from theoretical values and via the occurence of double Auger transitions, where one electron is emitted and another is excited. A critical examination of high resolution Auger spectra of noble gases, which has been measured so far, has shown that several non diagram lines can be assigned to double Auger transitions of the above kind.     

Auger electron spectroscopy - a local probe for solid surfaces

The Auger electron transition in solids is discussed under the aspect of a local excitation due to the strongly localized primary hole in an inner atomic core level. In first approximation the solid is represented by a cluster model, consisting of the excited atom and its neighbors. Using this simple model it is possible to describe the Auger electron energies, intensities and line shapes of transitions in solids in a satisfactory way. Only for the angular dependent Auger emission, characteristic long-range crystalline order has to be taken into account. It is the aim of this introductory review to point out that Auger spectra bear more information about the solid surface and particularly on its chemical bonds as has yet been exploited by surface spectroscopists.     

超高真空俄歇电子能谱原位加热和GaN热效应研究

建立一套基于超高真空俄歇电子能谱的原位加热系统,对GaN薄膜进行热效应研究．随着温度的增加,Ga LMM和Ga MVV的动能减小．利用第一性原理计算,获得理论的GaMVV俄歇谱.加热过程由于晶格热膨胀以及表面原子再构引起价电子态密度发生变化,从而导致价带俄歇谱负移．     

Auger and direct electron spectra in X-ray photoelectron studies of zinc,zinc oxide,gallium and gallium oxide

Auger and direct electron spectra from Zn, ZnO, Ga and Ga₂O₃ have been studied with X-ray photoelectron spectroscopy (ESCA). The chemical shift between zinc electron binding energies in Zn and ZnO is very small, whereas the zinc Auger electron signals are separated by 4.3 eV. In gallium, the oxide and metal signals are separated by 1.9 eV, but the Auger electron energy shift is three times as large. Thus the Auger signals are more sensitive to the chemical environment than the direct electron signals, which is the same relation as earlier observed for copper and copper oxides.     

Mechanisms of Auger recombination in semiconducting quantum dots

Microscopic calculation of the probability of Auger recombination of charge carriers localized in a semiconducting quantum dot (QD) is carried out. It is shown that two mechanism of Auger recombination (nonthreshold and quasi-threshold) operate in the QD. The nonthreshold Auger recombination mechanism is associated with scattering of a quasimomentum from a heterobarrier, while the quasi-threshold mechanism is connected with spatial confinement of the wave functions of charge carriers to the QD region; scattering of carriers occurs at the short-range Coulomb potential. Both mechanisms lead to a substantial enhancement of Auger recombination at the QD as compared to a homogeneous semiconductor. A detailed analysis of the dependence of Auger recombination coefficient on the temperature and QD parameters is carried out. It is shown that the nonthreshold Auger recombination process dominates at low temperatures, while the quasi-threshold mechanism prevails at high temperatures. The dependence of the Auger recombination coefficient on the QD radius experiences noticeable changes as compared to quantum wells and quantum filaments.     

Sputtering of SiC with low energy He and Ar ions under grazing incidence

The effect of low energy sputtering under grazing incidence upon the surface composition of SiC was investigated by Auger electron spectroscopy. The energy of the sputtering projectiles (He, Ar) varied from 200 to 1500?eV. Peak shifts to the higher energies with increasing argon ion energy were observed for all silicon and carbon Auger transitions. These shifts were explained by enhanced damage of the surface region within the sampling depth of the Auger electrons. The insensitivity of the Auger peak position to the energy of helium ions indicates that the damage state in the surface region does not change with the increasing energy of helium ions. An increase of the carbon concentration with the decrease of the argon energy was observed. The experiments were accompanied by dynamic Monte Carlo simulations by the TRIDYN code.