We describe a model for the study of the interaction of short X-ray Free-Electron Laser (XFEL) pulses with large finite samples. Hydrodynamics is solved in one-dimensional planar geometry with consideration of the electron-ion energy exchange and of the possible elasto-plastic behavior. From a time-dependent calculation of the complex refractive index and of the underlying atomic physics, XFEL energy deposition is modeled through a calculation of the radiation field in the material. In the case of hard X-ray irradiation, energetic electrons induced by the XFEL absorption can propagate and deposit their energy outside the interaction region. Simulations of the interaction of hard X-ray ultrashort pulses with solid materials Ru and Si at different grazing incidence angles are presented and discussed. The results obtained demonstrate the potential of this approach to predict damage dynamics for materials of interest for X-ray optics. PACS numbers: 52.65.-y, 41.50.th, 42.55.Vc, 52.25.Os ∗Electronic address: olivier.peyrusse@univ-amu.fr

En nous appuyant sur l'effet Purcell, nous présentons tant théoriquement qu'expérimentalement une étude montrant qu'il est possible de contrôler (inhiber ou au contraire exalter) l'émission spontanée de rayonnement X au moyen d'un cristal photonique mono-dimensionnel (1-D). Nous présentons tout d'abord un modèle de calcul du taux d'émission spontanée dans une telle structure, basé sur la règle d'or de Fermi dans le cadre de l'approche dite « Wigner-time ». Ce modèle est appliqué au cas de l'émission Si-K pour un cristal photonique 1-D formé par une structure multicouche périodique Mo/Si. Les simulations numériques sont comparées à l'expérience.

Extract HTML view is not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button. Extended abstract of a paper presented at Microscopy and Microanalysis 2005 in Honolulu, Hawaii, USA, July 31--August 4, 2005

Substrate surface preparation before chemical vapor deposition is an important step for the adhesion. This study describes the influence of the temperature and the RF bias during in-situ argon plasma treatment on TA6V substrates just before Plasma Enhanced Chemical Vapor Deposition (PECVD) of alumina. Substrates were treated under oxygen plasma without introducing aluminum precursor during 90 seconds under process PECVD conditions that were later used for coatings development. The surface of the samples is analyzed by Electron induced X-ray Emission Spectroscopy to study the physicochemical environment around the aluminum atoms. Atomic Force Microscopy (AFM) allowed to show the treatment impact on the surface morphology of the substrates. Coatings were characterized by the multicracking 4-point bending test. The results pointed out that the polarization value has a minor effect, whereas the temperature has a major influence.

This work is a contribution to the identification of the spectral components observed in the electroluminescence (EL) of insulating polymers. The approach aims at improving our current understanding of the nature of the interactions between electrical charges and the host material. In previous studies of poly(ethylene 2,6-naphthalate)-PEN, we have shown that some spectral features of the light emitted under high field could be associated with polymer degradation since they are not characteristic of the photophysical behavior of the material as probed by using mild UV-photons in photoluminescence experiments. So long as the nature of the degradation mechanism is not identified, support to this hypothesis can be brought considering other sources of excitation of the material that are likely to produce significant chemical degradation. Cathodoluminescence has been used in this respect, and a comparison between electro-, photo-, and cathodo-luminescence spectra is proposed. Some features of the EL spectrum that cannot be interpreted on the basis of the photoluminescence spectrum are present in the cathodoluminescence spectrum. Consideration of the excitation mechanisms in the three kinds of experiment gives conclusive evidence of material degradation signatures in the EL spectrum.

Measurements of long-wavelength x-rays emitted by light elements can be achieved by using selected layered synthetic microstructures (LSM). For both C Kα and N Kα radiation, W/Si (d = 3.25 nm) LSM was used. Because of the counter efficiency, the C Kα emission has the highest intensity in spite of a calculated reflectivity of the W/Si LSM in favor of the N Kα emission. For B Kα radiation, Mo/Si (d = 5.0 nm), B/Si (d = 4.6 nm) and Ni/C (d = 4.8 nm) LSM were used. Ni/C LSM is the best LSM for the B Kα range because in B/Si LSM the presence of boron gives rise to the anomalous diffusion phenomenon. The intensity, peak-to-background ratio and experimental resolution are better for Ni/C than for Mo/Si LSM. Copyright © 1999 John Wiley & Sons, Ltd.

The model called IntriX, designed bet interpret quantitatively electron probe analysis data, was tested via confrontations between its results and experimental or Monte Carlo data, These confrontations were established for in-depth ionization distributions Phi(rho z) and characteristic x-ray relative intensities in cases of homogeneous and stratified samples, and for wide ranges of incident beam energies (1.15 < E-0 < 30 keV) and overvoltages (1.3 < E-0/E-S < 10), Measurements are presented that allow the performance of IntriX to be tested in the low-energy range (E-0 < 5 keV). (C) 1998 John Wiley & Sons, Ltd.

Copper films evaporated on argon-oxygen plasma-treated poly(phenylene-vinylene) films have been studied by scratch test, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The adhesion of the metallic film to the polymer substrate was greatly enhanced after treatment and found to increase with the treatment time. SEM observation of the treated samples revealed that the morphology of the polymer surface was gradually changed with the treatment time as compared with that of the bare polymer film. On the other hand, XPS analysis of the polymer-metal interface showed that the bonding between carbon, oxygen and copper were subsequently modified as compared with those obtained in untreated samples. The high adhesion strength observed on these substrates was related to the modification in the surface morphology on the one hand and to the formation of new compounds at the polymer-metal interface on the other. The nature of the interfacial layer and its influence on the adhesion of the copper layer was discussed by comparing the results with those obtained in poly(phenylene-vinylene) (PPV)-Al systems.

Electron-induced x-ray emission spectroscopy (EXES) is an efficient technique to study the physicochemical properties of thin films and of buried interfaces. This method analyzes the distribution of the valence states, i.e. the states sensitive to the environment, in a selective way with the depth. The selectivity comes from the use of ionizing particles (electrons) gradually loosing their energy in the matter. Then the incident electron energy can be chosen in order to probe a given thickness of the material under study. Relation between chemical bond and atomic structure is discussed in the case of bare dielectrics (Al 2 O 3 and MgO). Applications to buned metal-dielectric interfaces (AuPd/Al 2 O 3 and Cu/MgO) are discussed as a function of mechanical properties.

Density of states (DOS) in GaSb/Al0.3Ga0.7Sb systems are studied by electron-induced x-ray emission spectroscopy (EXES) and compared to previous results we have obtained for GaAs/Al0.3Ga0.7As systems. The Al 3p valence DOS are analyzed in the bulk ternary compounds, in heterostructures, and in interfacial zones 30 Angstrom thick, this thickness being equivalent to that of heterostructure layers. Large changes of the Al 3p valence DOS are seen, depending on the preparation conditions of the samples whose quality was checked by photoluminescence. For heterostructures having a small interface roughness, localization of states on the whole valence band of barriers is evidenced. This localization is attributed to bidimensional effects that largely dominate the interface effects. In contrast, for heterostructures having interfaces of lower quality, interface interaction and localization are competitive, Core excitonic transitions seen by EXES confirm that localization of Al states in the barriers exists for superlattices with abrupt interfaces.

Using a convex crystal spectrometer, a numerical method was elaborated which allows one to determine the linear size of an x-ray source from the measure of spectral linewidths. This method was applied to the determination of the size of a very brief spark, produced by a high-voltage discharge near tungsten and iron tips, It is shown that, under the experimental conditions, the broadening geometric effect related to the size predominates over all the other broadening effects.

AbstractUtilisant un spectromètre à cristal convexe, une méthode numérique à été mise au point qui permet de déterminer la taille linéaire d'une source x à partir de la mesure des largeurs spectrales des raies x. Cette méthode à été appliquée à la détermination de la taille d'une étincelle très brève, produite par décharge haute tension au voisinage de pointes de tungstène et de fer. On montre que, dans les conditions d'expérience, l'effet d'élargissement géométrique lié à la taille prédomine sur tous les autres effets d'élargissement.

The partial Al and O valence spectral densities of alpha- and gamma-alumina in bulk and in the superficial zone of the samples are investigated using x-ray emission spectroscopy induced by electrons. These valence states are mixed over the whole width of the band. We show that changes in the atomic environment affect the hybridization of states in a narrow energy range. For the gamma-phase and superficial zones of the two phases, increased hybridization is observed. This is correlated with an increase in the covalent character of Al-O bonds at the surface and the gamma-phase. Defect states are observed both in the gap between O 2s and O 2p states and in the optical gap; for the alpha-phase, a structure is seen at about 1 eV above the top of the valence band which we interpret as due to an oxygen-vacancy state.

Electronic structure of nickel-aluminium interface is studied on both experimental and theoretical sides. Spectral densities of states are investigated by electron stimulated X-ray emission spectroscopy, each metal at the interface being analysed separately. Theoretical densities of states are obtained using a one electron tight binding scheme associated with a recursion method. Experimental as well as theoretical results show a similar behaviour of the Ni 3d states at interface and in the bulk. On the contrary the sp conduction band of aluminium at interface differs strongly from the bulk one; this change is theoretically interpreted as a coupling of the Al sp-Ni 3d states.