Philippe Jonnard

Structural properties of Al/Mo/SiC multilayers with high reflectivity for extreme ultraviolet light

We present the results of an optical and chemical, depth and surface study of Al/Mo/SiC periodic multilayers, designed as high reflectivity coatings for the extreme ultra-violet (EUV) range. In comparison to the previously studied Al/SiC system, the introduction of Mo as a third material in the multilayer structure allows us to decrease In comparison to the previously studied Al/SiC system with a reflectance of 37% at near normal incidence around 17 nm, the introduction of Mo as a third material in the multilayer structure allows us to decrease the interfacial roughness and achieve an EUV reflectivity of 53.4%, measured with synchrotron radiation. This is the first report of a reflectivity higher than 50% around 17 nm. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS) measurements are performed on the Al/Mo/SiC system in order to analyze the individual layers within the stack. ToF-SIMS and XPS results give evidence that the first SiC layer is partially oxidized, but the O atoms do not reach the first Mo and Al layers. We use these results to properly describe the multilayer stack and discuss the possible reasons for the difference between the measured and simulated EUV reflectivity values.

Comparison of Mg-based multilayers for solar He II radiation at 30.4 nm wavelength

Mg-based multilayers, including SiC/Mg, Co/Mg, B(4)C/Mg, and Si/Mg, are investigated for solar imaging and a He II calibration lamp at a 30.4 nm wavelength. These multilayers were fabricated by a magnetron sputtering method and characterized by x-ray reflection. The reflectivities of these multilayers were measured by synchrotron radiation. Near-normal-incidence reflectivities of Co/Mg and SiC/Mg multilayer mirrors are as high as 40.3% and 44.6%, respectively, while those of B(4)C/Mg and Si/Mg mirrors are too low for application. The measured results suggest that SiC/Mg, Co/Mg multilayers are promising for a 30.4 nm wavelength.

Characterization of Al and Mg alloys from their X-ray emission bands.

The valence states of Mg-Al alloys are compared to those of reference materials (pure Mg and Al metals, and intermetallics). Two methods based on X-ray emission spectroscopy are proposed to determine the phases and their proportion: first, by analyzing the Al valence spectra of the Mg-rich alloys and the Mg valence spectra of the Al-rich alloys; second, by fitting with a linear combination of the reference spectra the Al spectra of the Al-rich alloys and the Mg spectra of the Mg-rich alloys. This enables us to determine that Al and Al3Mg2 are present in the 0-43.9 wt% Al composition range and Mg and Al12Mg17 are present in the 62.5-100 wt% Al composition range. In the 43.9-62.5% Al range, the alloy is single phase and an underestimation of the Al content of the alloy can be estimated from the comparison of the bandwidth of the alloy spectrum to the bandwidths of the reference spectra.

Stokes reciprocity equations and density of modes for absorbing stratified media

One considers the influence of absorption on Stokes reciprocity equations and on the density of modes (DOM) for stratified media. The reciprocity equations are extended to absorbing media by using the transfer matrix formalism and introducing a special complex conjugation. A method of calculation for the DOM is presented in the Wigner-time approach and applied to periodic and quasi-periodic absorbing stratified structures. Examples of the role of absorption are given in the soft-X-ray domain.

Insulator gap states at the Cu/MgO(001) interface by X-ray emission spectroscopy

Abstract The energy distribution of oxygen 2p states is studied at the Cu/MgO(100) interface in a zone of 1.5xa0nm buried under a 10xa0nm thick copper film. Occupied oxygen states are evidenced in the MgO band gap. The results are deduced from an analysis of the Oxa01s–2p emission induced by an electron beam. With such probe particles, the ionization of the Oxa01s hole is produced selectively in the depth, making possible the Oxa01s–2p emission in a chosen thickness located at the interface. Only the p states whose wave functions overlap the Oxa01s wave function are involved in the emission. This condition gives a local character to the experimental method and, consequently, the states seen in the band gap are characteristic of oxygen.

Study of the adhesion between a-CH films and TA6V substrates by electron-induced X-ray emission spectroscopy (EXES)

Abstract The Ti 3d valence states have been analyzed by electron-induced soft X-ray emission spectroscopy (EXES) in the TA6V bulk alloy and at a-CH/TA6V and a-SiO x C y H/TA6V interfaces. These states stem from metallic titanium in both cases. In contrast, EXES analysis shows that aluminum is in an oxide environment. Both aluminium compounds have a different behaviour depending on the presence of a-SiO x C y H in contact with the alloy. Adherence of a-CH films on the TA6V alloy can be explained from physicochemical interactions.

On the Kramers–Kronig transform with logarithmic kernel for the reflection phase in the Drude model

We use the Kramers–Kronig transform (KKT) with logarithmic kernel to obtain the reflection phase and, subsequently, the complex refractive index of a bulk mirror from reflectance. However, there remains some confusion regarding the formulation for this analysis. Assuming the damped Drude model for the dielectric constant and the oblique incidence case, we calculate the additional terms: phase at zero frequency and Blashke factor and we propose a reformulated KKT within this model. Absolute reflectance in the s-polarization case of a gold film is measured between 40 and 350 eV for various glancing angles using synchrotron radiation and its complex refractive index is deduced using the reformulated KKT that we propose. The results are discussed with respect to the data available in the literature.

Importance of the mixing of valence states on adhesion at solid/solid interfaces

Abstract We show, by means of two different examples, that good adhesion between solids can be achieved if mixing exists between the valence states of both materials present at the interface. We use X-ray emission spectroscopy induced by electrons. For a metal/ceramic interface (AuPd/Al 2 O 3 ), by comparing spectra from samples obtained by sputtering in the presence or absence of oxygen, we observe that the mixing between valence states increases with the mechanical and thermal qualities of the multilayer. For a polymer/metal interface [polyacrylonitrile (PAN)/Ni] we compare samples with the polymer deposited on the metallic substrate either by cathodic electropolymerization or by simply dipping the metal into a PAN solution. In the former case it is not possible to completely dissolve the polymer layer, and we observe Ni3d-C 2p mixing at the interface. In the other case, no mixing of valence states is seen and the polymer layer can be completely dissolved.

X‐ray Spontaneous Emission Control By 1D‐PBG Structure

The control of the decay rate of an excited atom through the photonic mode density (PMD) was pointed out at radiofrequency by Purcell in 1946. Nowadays the development of sophisticated photonic band structures makes it possible to monitor the PMD at shorter radiation wavelengths and then to manipulate the spontaneous emission of atoms in the hard region of the electromagnetic spectrum especially in the visible domain. In this communication we study the possibility of monitoring the x‐ray emission by means of one‐dimensional photonic band structures such as periodic multilayer systems. Enhancement or inhibition of soft x‐ray emissions seems now to be feasible by means of the state‐of‐the art in x‐ray optics.