[en] Ultrathin compressively strained SiGe layers is one of the most promising materials for high mobility channels of p-type metal oxide semiconductor field effect transistors (pMOSFETs). Fabrication of such layers by SiGe thermal oxidation processes need to be well controlled, which then require well-controlled oxidation kinetics and oxide properties for use in an industrial environment. In the present paper, we address oxidation kinetics of Si, Si_0.9Ge_0.1 and Si_0.7Ge_0.3 by means of dry furnace oxidation and dry rapid thermal oxidation (RTO). We showed in a previous paper that oxidation of SiGe by means of either dry furnace oxidation or dry RTO is limited by diffusion of the oxidizing species through the growing oxide and that the oxidation rate of SiGe is significantly higher than the one of Si. In the present paper we focus on the influence of the oxide density measured by Soft x-ray Reflectivity on oxidation kinetics. It is shown that the lower the density of the oxide is, the higher the oxidation rate is, in agreement with an oxidation regime that is governed by diffusion of O₂ through the growing oxide. Finally, we propose a model of O₂ diffusivity that depends on the oxide density through the modulation of the diffusion barrier. The modulation of the diffusion barrier is found to be linearly dependent on the oxide density. (paper)

[en] Optical activity (OA) was only recently discovered in the x-ray range. It is caused mainly by the electric dipole-electric quadrupole E1E2 interference terms which mix multipole moments of opposite parity and exist only in structures with odd space parity. OA related phenomena can be either even or odd with respect to time reversal: natural OA is concerned with time-reversal even effects whereas non-reciprocal OA refers to time-reversal odd contributions. Various types of x-ray dichroisms related to either natural or non-reciprocal OA have been detected and are reviewed in the present paper. Extra emphasis is put on two different non-reciprocal effects that were observed in selected magnetoelectric materials: (i) x-ray magnetochiral dichroism (XMχ D) and (ii) the non-reciprocal x-ray magnetic linear dichroism. Edge-selective OA sum rules have recently been established which show that the effective operator of XMχ D is the orbital anapole moment at the absorbing centre

[en] We discuss how measurements of x-ray circular intensity differentials (XCIDs) could be used to probe the Voigt-Fedorov vector part of optical activity (OA) due to electric dipole-electric quadrupole (E 1E 2) interferences. The first experiment was carried out on a single crystal of zincite (hexagonal ZnO: class 6mm). XCID spectra were recorded in the x-ray resonant diffraction regime near the Zn K edge using the (300) reflection at Bragg angles near 45 deg. In the x-ray range, the effective operator responsible for the vector part of OA can be assigned to the vector product LxΩ_L-Ω_LxL∝n, in which L and Ω_L are time-reversal odd operators associated with the orbital angular momentum and the orbital anapole respectively, whereas n is a true time-reversal even electric dipole. This is consistent with the pyroelectric properties of zincite crystals

[en] The deuterium enrichment of organics in the interstellar medium, protoplanetary disks, and meteorites has been proposed to be the result of ionizing radiation. The goal of this study is to simulate and quantify the effects of soft X-rays (0.1–2 keV), an important component of stellar radiation fields illuminating protoplanetary disks, on the refractory organics present in the disks. We prepared tholins, nitrogen-rich organic analogs to solids found in several astrophysical environments, e.g., Titan’s atmosphere, cometary surfaces, and protoplanetary disks, via plasma deposition. Controlled irradiation experiments with soft X-rays at 0.5 and 1.3 keV were performed at the SEXTANTS beamline of the SOLEIL synchrotron, and were immediately followed by ex-situ infrared, Raman, and isotopic diagnostics. Infrared spectroscopy revealed the preferential loss of singly bonded groups (N–H, C–H, and R–N≡C) and the formation of sp³ carbon defects with signatures at ∼1250–1300 cm⁻¹. Raman analysis revealed that, while the length of polyaromatic units is only slightly modified, the introduction of defects leads to structural amorphization. Finally, tholins were measured via secondary ion mass spectrometry to quantify the D, H, and C elemental abundances in the irradiated versus non-irradiated areas. Isotopic analysis revealed that significant D-enrichment is induced by X-ray irradiation. Our results are compared to previous experimental studies involving the thermal degradation and electron irradiation of organics. The penetration depth of soft X-rays in μ m-sized tholins leads to volume rather than surface modifications: lower-energy X-rays (0.5 keV) induce a larger D-enrichment than 1.3 keV X-rays, reaching a plateau for doses larger than 5 × 10²⁷ eV cm⁻³. Synchrotron fluences fall within the expected soft X-ray fluences in protoplanetary disks, and thus provide evidence of a new non-thermal pathway to deuterium fractionation of organic matter.

[en] A soft x-ray spectrometer based on the use of an elliptical focusing mirror and a plane varied line spacing grating is described. It achieves both high resolution and high overall efficiency while remaining relatively compact. The instrument is dedicated to resonant inelastic x-ray scattering studies. We set out how this optical arrangement was judged best able to guarantee performance for the 50 − 1000 eV range within achievable fabrication targets. The AERHA (adjustable energy resolution high acceptance) spectrometer operates with an effective angular acceptance between 100 and 250 μsr (energy dependent) and a resolving power well in excess of 5000 according to the Rayleigh criterion. The high angular acceptance is obtained by means of a collecting pre-mirror. Three scattering geometries are available to enable momentum dependent measurements with 135°, 90°, and 50° scattering angles. The instrument operates on the Synchrotron SOLEIL SEXTANTS beamline which serves as a high photon flux 2 × 200 μm² focal spot source with full polarization control