A5102779934- Advanced X-ray Imaging Techniques
- Advanced Electron Microscopy Techniques and Applications
- X-ray Spectroscopy and Fluorescence Analysis
- Electron and X-Ray Spectroscopy Techniques
- Crystallography and Radiation Phenomena
- Particle Accelerators and Free-Electron Lasers
- Magnetic properties of thin films
- Semiconductor materials and devices
- Laser-Plasma Interactions and Diagnostics
- Liquid Crystal Research Advancements
- Organic Electronics and Photovoltaics
- Machine Learning in Materials Science
- Electronic and Structural Properties of Oxides
- Advanced Chemical Physics Studies
- Atomic and Molecular Physics
- Laser-Matter Interactions and Applications
- X-ray Diffraction in Crystallography
- Magneto-Optical Properties and Applications
- Semiconductor materials and interfaces
- Photochemistry and Electron Transfer Studies
- Polymer crystallization and properties
- Particle accelerators and beam dynamics
- Integrated Circuits and Semiconductor Failure Analysis
- Ion-surface interactions and analysis
- Copper Interconnects and Reliability
Helmholtz-Zentrum Berlin für Materialien und Energie
2018-2024
Sorbonne Université
2011-2022
Laboratoire de Chimie Physique - Matière et Rayonnement
2012-2022
Centre National de la Recherche Scientifique
2008-2022
Synchrotron soleil
2013-2021
Université Paris Cité
2014-2017
Max-Born-Institute for Nonlinear Optics and Short Pulse Spectroscopy
2017
Deutsches Elektronen-Synchrotron DESY
2017
Université Paris-Saclay
2012
Stanford Synchrotron Radiation Lightsource
2001-2011
We used near-edge x-ray absorption fine structure (NEXAFS) spectroscopy to link the orientational bond order at three carbonaceous surfaces-rubbed polyimide, ion beam-irradiated and diamondlike carbon films-with direction of liquid crystal (LC) alignment on these surfaces. show that, in general, LC can be created any substrate by inducing its surface. Our results form scientific basis for layers consisting amorphous films which near surface is induced a directional low-energy beam.
We present the first single-shot images of ferromagnetic, nanoscale spin order taken with femtosecond x-ray pulses. X-ray-induced electron and dynamics can be outrun pulses shorter than 80 fs in investigated fluence regime, no permanent aftereffects samples are observed below a 25 mJ/cm2. Employing resonant spatially muliplexed holography results low imaging threshold 5 Our open new ways to combine ultrafast laser spectroscopy sequential snapshot on single sample, generating movie excited...
Measurements of the spatial and temporal coherence single, femtosecond x-ray pulses generated by first hard free-electron laser, Linac Coherent Light Source, are presented. Single-shot measurements were performed at 780 eV photon energy using apertures containing double pinholes in "diffract-and-destroy" mode. We determined a length 17 μm vertical direction, which is approximately size focused Source beam same direction. The analysis diffraction patterns produced with largest separation...
Near edge x-ray absorption fine structure (NEXAFS) spectroscopy has evolved into a powerful characterization tool for polymeric materials and is increasingly being used to elucidate composition orientation in thin films of relevance organic electronic devices. For accurate quantitative compositional analysis, insight the ability assess molecular orientation, reliable reference spectra with known energy resolution calibrated scale are required. We report set such NEXAFS from 23 semiconducting...
The soft x-ray materials science instrument is the second operational beamline at linac coherent light source free electron laser. operates with a photon energy range of 480-2000 eV and features grating monochromator as well bendable refocusing mirrors. A broad experimental stations may be installed to study diverse scientific topics such as: ultrafast chemistry, surface science, highly correlated systems, matter under extreme conditions, laboratory astrophysics. Preliminary commissioning...
The crystallization of poly(ethylene−vinyl acetate) and linear low-density polyethylene (LLDPE) films spun-cast from the polymer/toluene solutions with as-cast thickness 460 to 10 nm was studied. lamellar measured using small-angle X-ray scattering (SAXS) found increase 14 21 for thinner than 100 nm. morphology LLDPE by scanning probe microscopy (SPM) showed an edge-on lamellae thicker 30 flat-on 15 A pseudo-"shish-kebab" tiny crystal structure observed in between larger lamellae....
The authors demonstrate multiple reference source Fourier transform holography with soft x rays. This technique extends the detection limit of high resolution lensless imaging by introducing spatial multiplexing to coherent x-ray scattering. In this way, image quality is improved without increasing radiation exposure sample. especially relevant for recording static images sensitive samples and studying dynamics pulsed light sources. Applying their in weak illumination they a nanoscale test...
We present the x-ray optical design of soft materials science instrument at Linac Coherent Light Source, consisting a varied line-spaced grating monochromator and Kirkpatrick-Baez refocusing optics. Results from commissioning are shown. A resolving power 3000 was achieved, which is within factor two goal.
We report x-ray magnetic linear dichroism (XMLD) measurements at the Fe ${L}_{2,3}$ absorption edges of thin antiferromagnetic (AFM) ${\mathrm{LaFeO}}_{3}$ films grown epitaxially on ${\mathrm{SrTiO}}_{3}$ (100) and (110) substrates a stepped substrate with 2\ifmmode^\circ\else\textdegree\fi{} miscut. The spin structure in near-surface region films, particular orientation AFM axis, has been derived from observed polarization dependence. show that all cases, axis differs bulk...
The recent development of x-ray free electron lasers providing coherent, femtosecond-long pulses high brilliance and variable energy opens new areas scientific research in a variety disciplines such as physics, chemistry, biology. Pump-probe experimental techniques which observe the temporal evolution systems after optical or pulse excitation are one main schemes currently use for ultrafast studies. key challenge these experiments is to reliably achieve spatial overlap pulses. Here we...
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 overall efficiency while remaining relatively compact. The instrument dedicated to resonant inelastic scattering studies. We set out how this optical arrangement was judged best able guarantee performance for 50 − 1000 eV range within achievable fabrication targets. AERHA (adjustable energy acceptance) operates with effective...
X-ray absorption spectroscopy (XAS) is used to study band edge electronic structure of high-/spl kappa/ transition metal (TM) and trivalent lanthanide rare earth (RE) oxide gate dielectrics. The lowest conduction d/sup */-states in TiO/sub 2/, ZrO/sub 2/ HfO/sub are correlated with: 1) features the O K/sub 1/ edge, 2) transitions from occupied Ti 2p, Zr 3p Hf 4p states empty 3d-, 4d-, 5d-states, respectively. relative energies d-state indicate that respective optical bandgaps, E/sub opt/ (or...
We demonstrate phase imaging by means of resonant soft x-ray holography. Our holographic phase-contrast method utilizes the strong energy-dependence refractive index at a characteristic absorption resonance. The general concept is shown using $\mathrm{Co}∕\mathrm{Pd}$ multilayer sample which exhibits random nanosized magnetic domains. By tuning below Co $L$-edge resonance, our quantitative and spectroscopic allows high-contrast nanoscale electronic order while increasing probing depth...
We present results of single-shot resonant magnetic scattering experiments Co/Pt multilayer systems using 100 fs long ultraintense pulses from an extreme ultraviolet (XUV) free-electron laser. An x-ray-induced breakdown the channel during pulse duration is observed at fluences 5 J/cm(2). Simultaneously, speckle contrast high-fluence pattern significantly reduced. performed simulations nonequilibrium evolution system XUV duration. find that electronic state sample strongly perturbed first few...
A new device for polarization control at the free electron laser facility FLASH1 DESY has been commissioned user operation. The polarizer is based on phase retardation upon reflection off metallic mirrors. Its performance characterized in three independent measurements and confirms theoretical predictions of efficient broadband generation circularly polarized radiation extreme ultraviolet spectral range from 35 eV to 90 eV. degree circular reaches up 90% while maintaining high total...
Panoramic full-field imaging is demonstrated by applying spatial multiplexing to Fourier transform holography. Multiple object and reference waves extend the effective field of view for lensless without compromising resolution. In this way, local regions interest distributed throughout a sample can be simultaneously imaged with high A method proposed capturing multiple ultrafast images single x-ray pulse.
Seeded free electron lasers theoretically have the intensity, tunability, and resolution required for multiphoton spectroscopy of atomic molecular species. Using seeded laser FERMI a novel detection scheme, we revealed two-photon excitation spectra dipole-forbidden doubly excited states in helium. The spectral profiles lowest $(\ensuremath{-}1,0{)}^{+1}$ $^{1}{S}^{e}$ $(0,1{)}^{0}$ $^{1}{D}^{e}$ resonances display energy shifts meV range that depend on pulse intensity. results are explained...
Ultrashort optical pulses can trigger a variety of non-equilibrium processes in magnetic thin films affecting electrons and spins on femtosecond timescales. In order to probe the charge degrees freedom simultaneously, we developed an x-ray streaking technique that has advantage providing jitter-free picture absorption cross section changes. this paper, present experiment based approach which performed using five photon probing energies at Ni $M_{2,3}$-edges. This allowed us retrieve circular...
We measure the light-driven response of a magnetic multilayer structure made thin alternating layers cobalt and platinum at few-femtosecond timescale. Using attosecond circular dichroism, we observe how light rearranges moment during after excitation. The results reveal sub-5 fs spike magnetization in layer, which follows shape driving pulse. With help time-dependent density functional theory, interpret observations as spin injection across metallic structure. light-triggered current is...
We present resonant coherent small-angle scattering from $\mathrm{s}\mathrm{u}\mathrm{b}\ensuremath{-}\ensuremath{\mu}\mathrm{m}$ magnetic domains in an in-line holography geometry. By varying the polarization of incident soft x rays interference between reference wave propagating a pinhole and scattered object can be switched ``on'' or ``off.'' The reference-object contribution isolated by combining measurements with right left circular polarizations. implications for spatial temporal...
Monodisperse, low molecular weight poly(2,5-di(2'-ethylhexyloxy)-1,4-phenylenevinylene) (DEH-PPV) demonstrates significantly better structural order than polydisperse PPVs. Since optical and electrical properties of polymer electronics are closely related to the structure morphology active layer, morphological control is important for fabrication PPV-based devices. Soluble, monodisperse DEH-PPVs with a range weights showed sequence transitions through crystalline, smectic, nematic, isotropic...
We have used X-ray absorption near-edge fine-structure (XANES) analysis of oxygen K-edges in combination with high-resolution transmission electron microscopy to investigate phase separation Hf-silicate thin films subjected high temperature anneals. show that the K-edge fine structures can, a first approximation, be interpreted as an overlap features from amorphous silica and crystalline hafnia phases separated microstructures. Increasing amounts samples resulted increase bulk silica-like...
We demonstrate that resonant inelastic soft x-ray scattering can be used to study the electronic band structure of SiC quantitatively. Band mapping is enabled by crystal momentum selectivity, due conservation in process. Additionally, dipole transition-matrix elements which govern intensity absorption-emission process lead a projection states on atomic sites and local angular-momentum symmetry. This yields unique band-structure information about spatial distribution symmetry character...