Nonlinear absorption, linear optical properties and structure of CdSXSe1−X microcrystallites in glass matrix

It was found that optical properties and nonlinearity of semiconductor microcrystallites in glass matrix are determined mainly by their structure. We established that the Auger recombination and the traps filling are responsible for the intensity dependence of transmission at picosecond and nanosecond pump respectively. The probabilities of linear and Auger recombination as a function of intensity have been obtained by computer simulation.     

Auger energy shifts in fcc AgPd random alloys from complete screening picture and experiment

We extend the complete screening picture to ab initio calculations of Auger kinetic energy and Auger parameter shifts in metallic alloys. Experimental measurements of the L(3)M(4,5)M(4,5) Auger transition in fcc AgPd random alloys are compared with first-principles calculations and the results are in excellent agreement for both the Ag and Pd Auger shifts over the whole concentration range. We discuss the Auger kinetic energy shifts in terms of single-hole states for the 2p(3/2) core level and double-hole states for the 3d(5/2) level.     

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.     

Thermal and optical studies of an amorphous InSe9 alloy produced by mechanical alloying

In this paper we investigated thermal and optical properties of an amorphous alloy of the In–Se system. The amorphous InSe₉ alloy was produced by mechanical alloying and it was studied using Differential Scanning Calorimetry and microPhotoluminescence spectroscopy techniques, and from them several properties, such as glass transition and crystallization temperatures and energies and the optical gap energy were determined and compared to the values found in other alloys of the In–Se system. This comparison revealed some differences among our alloy produced by mechanical alloying and alloys produced by other techniques, which is a clear indication of the influence of the fabrication technique in their physical properties. The main differences occur in the activation energies associated with the glass transition and crystallization processes and also in the optical gap energy.     

Determination of the surface composition of palladium-nickel alloy film catalysts using Auger electron spectroscopy

Palladium-nickel films evaporated in UHV on room temperature substrates form alloys of good bulk homogeneity as indicated by X-ray diffraction. The average composition of the outermost 3 to 5 atom layers has been determined from the intensities of the high energy 848 eV nickel and 330 eV palladium Auger electrons. This average composition is in close agreement with the bulk composition determined by X-ray diffraction, X-ray fluorescence and atomic absorption spectrophotometry. If the nickel concentration is determined from the intensity of the low energy 61 eV nickel Auger electrons, when the analysis refers more critically to the first 1 to 3 atom layers, then a surface enrichment of palladium is indicated for all alloy compositions. From the decrease in the relative intensities of the low energy and high energy nickel Auger electrons with increasing palladium concentration it may be deduced that the enrichment of palladium in the first atom layer is higher than in the second and third layers and that a complete monolayer of palladium is formed for bulk concentrations of 65 at% or more. The experimental observations are in qualitative agreement with theoretical predictions of surface composition from bulk thermodynamic data. The palladium-nickel alloys form a range of surface compositions which can be controlled by changing the bulk composition and which are useful for studying catalytic activity as a function of composition. The alloy films are stable under electron irradiation in the AES analysis in UHV but air exposed films analysed in a residual pressure of 1.3 microPa water vapour show a decrease in palladium surface concentration on irradiation indicating a diffusion of nickel to the surface to form an overlayer of nickel oxide.     

Disorder broadening of alloy Auger spectra

Auger spectroscopy promises the means to separate initial and final state contributions to the disorder broadening of core XPS spectra in disordered alloys. Auger disorder broadening, deduced from recent ab initio results, is predicted to be greater than XPS disorder broadening for Cu₅₀Pd₅₀ and Ag₅₀Pd₅₀ alloys. Simulations are used to assess whether this effect is observable experimentally despite the greater lifetime broadening of Auger spectra. A number of cases where narrow core–core–core Auger transitions should allow clear experimental identification of this effect are identified. The prospects for determining environment-resolved Auger spectra using APECS have been investigated.     

Influence of Auger recombination on the lifetime of nonequilibrium carriers in InGaAsSb/AlGaAsSb quantum well structures

Carrier recombination processes, including the Auger recombination, are studied in InGaAsSb/AlGaAsSb quantum well nanostructures. Based on the dynamics of photoluminescence, we estimate the emission time of an optical phonon, determined the recombination rate as a function of optical-excitation intensity, and estimated the coefficient characterizing the rate of the resonance Auger recombination.     

Core-level Auger spectroscopy of the 4d metals

We report some of the results of extensive experimental and theoretical studies by our group of the high energy Auger spectra of the 4d metals and some of their alloys. We consider, separately, three aspects of these spectra: comparison of experiment with atomic theoretical calculations; the relationship between the Auger kinetic energies and the screening mechanisms in these metals; and the unique properties of satellites associated with these spectra, especially with the L_1,2,3M_4,5M_4,5 spectra. Comparison with atomic theory yields some discrepancies that should be taken into account in the formulation of the theories. Consideration of the Auger kinetic energies yields insight into screening mechanisms and suggests methods for extracting electronic structure changes in alloys from XPS and XAES shifts. Systematic studies of the satellites permit their identification as arising from shake-up processes without contributions from of Coster–Kronig processes, in contrast to studies of 3d metals, such as Cu. Synchrotron studies allow the observation of the transition from the adiabatic approximation regime to that of the sudden approximation.     

Quantitative Auger electron spectroscopy analysis of binary alloys with separate matrix correction factors for bulk and surface

A new method which takes into account the separate matrix correction factors for bulk and surface has been tried out for quantitative Auger electron spectroscopy analysis of binary alloys. The calculations use an iteration scheme. It has been applied to the Fe-Cr alloys studied at this Centre and the Auger electron spectroscopy data for the other alloy systems available in literature. The results are now more compatible with the expectation that the surface composition is different from the bulk.     

Surface composition and depth concentration profile of platinum/tin alloys from combined X-ray photoelectron and Auger spectroscopic data

Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (X-PS) have been combined to study surface enrichment of two platinum/tin alloys, viz. PtSn and Pt₃Sn, effected by reduction in hydrogen at 550°C. By making use of the different information depths of AES and X-PS for this alloy system, as determined by the corresponding mean free paths of inelastic scattering of the emitted characteristic electrons, a rather detailed picture has been obtained of the composition of the topmost atomic layers in these alloys. It is shown that both alloys exhibit phenomena of surface enrichment and depletion of the underlying layers over distances of the order of 10 Å.     

First-principles calculations of the structural,electronic, optical and thermal properties of the BNxAs1–x alloys

The present paper aims to study the structural, electronic, optical and thermal properties of the boron nitride (BN) and BAs bulk materials as well as the BN_xAs_1–x ternary alloys by employing the full-potential-linearised augmented plane wave method within the density functional theory. The structural properties are determined using the Wu–Cohen generalised gradient approximation that is based on the optimisation of the total energy. For band structure calculations, both the Wu–Cohen generalised gradient approximation and the modified Becke–Johnson of the exchange-correlation energy and potential, respectively, are used. We investigated the effect of composition on the lattice constants, bulk modulus and band gap. Deviations of the lattice constants and the bulk modulus from the Vegard’s law and the linear concentration dependence, respectively, were observed for the alloys where this result allows us to explain some specific behaviours in the electronic properties of the alloys. For the optical properties, the calculated refractive indices and the optical dielectric constants were found to vary nonlinearly with the N composition. Finally, the thermal effect on some of the macroscopic properties was predicted using the quasi-harmonic Debye model in which the lattice vibrations are taken into account.     

The surface composition of platinum-palladium alloys determined by auger electron spectroscopy

Pt-Pd alloys were prepared as powders by a chemical reduction method and as films by evaporating the specpure metals onto a quartz substrate. Results were evaluated by means of the Gallon equation; the parameters of this equation — the signal intensity of a monolayer and of the bulk material — were determined experimentally for all relevant Auger peaks. The backscattering factor for the alloy system was evaluated from experiments in which a layer of one metal was evaporated on top of the other. The value determined in this way was compared with results obtained in the literature on similar systems. The theoretical surface compositions are calculated for several models and compared with the experimental results. Experimental results reveal surface enrichment in Pd, in good agreement with the theoretical calculations. Interactions of alloys with carbon monoxide and propane are discussed and a possible explanation of the effects observed is suggested.     

Secondary and auger electron spectra of a Cu-Be alloy

The slow secondary electron spectra corresponding to the copper rich surface and oxidized beryllium surface of Cu-Be alloys are observed after argon ion bombardment and heating treatment of the sample and they are identified by Auger electron spectroscopy.     

氮化钛薄膜的光学性能分析

利用磁控溅射法，在不同的工艺条件下制备氮化钛薄膜。详细分析了不同工艺条件下薄膜的光谱选择特性以及相应的光学常数，通过俄歇电子能谱对薄膜的不同深度的元素成分进行了分析，由原子力显微镜测量并处理得到氮化钛薄膜的表面形貌图。结果表明，氮化钛薄膜的光学性能严格依赖于氮和钛原子数比，符合化学计量比的TiN薄膜具有良好的光谱选择性。基底加负偏压溅射可进一步改善薄膜的性能。     

Incorporation of nitrogen into amorphous-hydrogenated carbon (diamond-like) films

Nitrogen-doped amorphous hydrogenated carbon films (a-C:H) were prepared by mixing nitrogen gas and benzene during dc plasma discharge deposition. The growth rate of the film decreases strongly with increasing nitrogen content in the mixture. The nitrogen concentration in the films was determined by nuclear reaction analysis (NRA) and Auger electron spectroscopy (AES) using suitable calibration samples. The results of AES measurements are generally consistent with NRA values. Nitrogen incorporation in the a-C:H films shows pronounced doping effects as reflected in their optical and electrical properties.Dedicated to Professor J. P. F. Sellschop for his 60^th birthday     

The surface composition of the nickel-copper alloy system as determined by Auger electron spectroscopy

The Ni-Cu alloys were prepared by evaporation of the specpure metals in UHV onto a quartz substrate. Spectra were obtained from clean as well as from gas covered surfaces. The Auger signal intensity of a monolayer of both metals was determined for the low energy electrons (102–105 eV) and for the high energy electrons (716–920 eV). The overlapping peaks of Cu and Ni in the low energy region (102–105 eV) were evaluated by comparing them with computer simulated alloy spectra. The results of the sintered alloys are interpreted by means of a model by Gallon and Jackson, using the experimentally determined signal intensity of a monolayer. Several surface enrichment data were used to predict the experimentally observed Auger signal intensities. A clear indication of surface enrichment of Cu was obtained; this is in good agreement with previous conclusions based upon hydrogen adsorption and work function measurements. An explanation is suggested why previous work with AES and CO chemisorption did not reveal any surface enrichment.     

An AES study of surface segregation of AgAu alloys with ion bombardment and annealing

Equilibrium segregation and selective sputtering in the surface of AgAu alloys have been investigated systematically with argon ion bombardment and with annealing by means of AES measurements. Slight enrichment of Ag was observed on the alloy surfaces after the annealing of the alloys at 550°C, while relatively large enrichment of Au was observed on the ion-bombarded surfaces with the use of Au (240 eV) and Ag (300 eV) Auger electrons. With the aid of other Auger electrons with different escape lengths, it was found that the concentration varies with distance from the surface within the sampling depth of the Auger electrons. On the basis of the above facts, the depth profiles were proposed for the annealed and the ion-bombarded surfaces. The uppermost surface layer is enriched more with Ag than the apparent AES observations on both the ion-bombarded and the annealed surfaces. The proposed depth profiles on both the surface layers were compared with previous results by different authors.     

Surface segregation in Pt-Au alloys studied using Auger electron spectroscopy

Temperature dependent surface segregation studies using Auger electron spectroscopy have been performed on three different Pt-Au alloys, containing 2, 5 and 90 wt% Au. By utilizing Auger transitions of different kinetic energies and model segregation profiles, an estimate of the in-depth variation in composition was made. Strong surface segregation of Au was observed in the three alloys.     

The role of photodarkening and Auger recombination in the dynamics of the optical response for Cd(S,Se) nanoparticles

We first recall the main linear optical properties of semiconductor-doped glasses in the strong confinement regime. We then discuss the origin of the photodarkening effect and its consequences on the luminescence and absorption spectra. Photodarkening and, at high excitation intensity, Auger processes strongly modify carrier recombination as studied by time-resolved luminescence measurements. This is further supported by using nonlinear optical techniques such as optical phase conjugation. We finally recall the origin of the nonlinear response of such media in the resonant regime and the size dependence of the corresponding figure of merit.     

Characterization of In/Pd and Pd/In/Pd thin films by ellipsometric, XRD and AES methods

In/Pd and Pd/In/Pd thin films were prepared by thermal evaporation on the SiO₂ substrate in a vacuum. The structural and optical properties of the films were investigated by means of X-ray diffractometry (XRD), Auger electron spectroscopy (AES) and spectroscopic ellipsometry (SE). Auger depth profile studies were performed in order to determine the composition of elements in the Pd-In systems. Interdiffusion of metals was detected at room temperature. Optical properties of Pd-In composite layers formed due to the interdiffusion were derived from ellipsometric quantities Ψ and Δ measured in the photon energy range 0.75-6.50 eV at different angles of incidence. The effective optical spectra show absorption peaks dependent on the composition of nonuniform films. The XRD patterns indicated formation of Pd_1−xIn_x intermetallic phases in the samples.