In situ studies of functional nano materials at large scale facilities: from model systems to applications

Resume : MnAs is a promising candidate for electrical spin injection into GaAs and Si based semiconductors, having large carrier spin polarization, small coercive field and relatively high saturation magnetization and Curie temperature. Bulk MnAs is ferromagnetic at room temperature (RT) (alpha phase) and shows, close to 40°C, a first order transition to the paramagnetic beta phase. Epitaxial MnAs films on GaAs, which are more appropriate for the injection applications, show the coexistence of both phases at RT. The effect has been widely studied in the last years by X-PEEM and LEEM. The phase coexistence results in the formation of self-organized stripes of alternating alpha/beta phases and is due to anisotropic strain applied by the substrate. Going one step further (i.e. miniaturizing for a magnetic device) one may wonder how the system magnetically reorganizes when the associated energies become smaller than the thermal energy. In the particular case of patterned MnAs thin films, what is the effect of the finite size on the strain release and the alpha/beta coexistence regime? Using X-ray micro-diffraction and LEEM we show that patterned samples can have very different micromagnetic behavior and thin film results cannot be extrapolated to patterned objects. The presence of the phases was quantified and the influence of parameters like the objects shape, size, aspect ratio was studied function of the temperature. A theoretical (elastic) model was developped and shows good agreement with the experimental results.

Resume : As a prototypical all-oxide heterostructure, the ferromagnetic insulator europium monoxide (EuO) is synthesized on transparent and conductive indium tin oxide (ITO) virtual substrates. Nondestructive hard X-ray photoelectron spectroscopy (HAXPES) is employed to depth profile the chemical composition of the magnetic layer and the buried oxide-oxide interface. We find that thermally activated oxygen diffusion from ITO affects the EuO growth process. We present how to control the oxygen reactivity at the interface and discuss its origin in a thermodynamic analysis. Our complementary methodical strategy allows for a significant improvement of the EuO chemical quality with sizeable magnetic properties. Generally, our approach derives guidelines for the proper choice of oxide substrates and buffer layer materials for functional all-oxide heterostructures.

Resume : Magnetization reorientation driven by short light pulses (both in the EUV and IR spectral range) has been recently found in thin Pt/Co/Pt films and explained in terms of irradiation induced formation of Co-Pt alloy on the Co/Pt interface, exhibiting high perpendicular magnetic anisotropy. In the present work we investigated the Pt/Co/Pt structures whose in-plane magnetization was modified by single light pulses duration of 40 fs and wavelength of 800 nm, emitted by IR laser. The Co layers 3 nm or 10 nm thick placed in-between the Pt bottom and top layers were deposited by MBE method onto (0001)-oriented sapphire substrates, applied Pt thickness ranged from 3 nm to 25 nm. The polarized neutron reflectivity (PNR) is an effective tool to study depth profiles of in-plane magnetization in two-dimensional structures and, to some extent, depth profiles of constituent element distribution. PNR measurements were performed at LLB with the use of PRISM spectrometer. Prior to the irradiation a presence of smooth and sharp interfaces was confirmed by X-ray reflectivity (XRR) and PRN methods, the sample structure was also characterized by X-ray diffraction (XRD). The analogous results obtained for irradiated samples showed changes in their structure and magnetic properties related to an asymmetry in the Co distribution along the normal to the sample surface. Work was partially supported by the grant No. DEC-2012/06/M/ST3/00475 from National Science Centre (Poland).

Resume : The electrochemical layer by layer growth represents an attractive alternative for the production of thin films of semiconductor compounds with high grade of crystallinity. Respect to vapor phase deposition or vacuum methods the electrochemical deposition presents several advantages: the low cost, the possibility of room-temperature operation and a very simple and strict control of the film composition and thickness. The electrochemical layer by layer growth of compounds is a method based on the alternate Underpotential Deposition (UPD) of the elements that form the compound. Being the UPD a surface-limited phenomenon it is possible to limit the electrodeposition process to one atomic layer and thus control the film thickness by controlling the number of alternate UPD deposition cycles. The ex-situ characterization of thin films grown by this method has shown that the sequential deposition of UPD layers results in an ordered multilayer structure, nevertheless several aspects of the growth process were not clear yet. In the present contribution we'll report the results of an in-situ Surface X-ray Diffraction study focused on the characterization of the layer by layer growth of CdS thin films on Ag(111). In-situ experiments allowed us to better understand the dynamics of the growth, record structural changes of the order of the in-plane structure and collect information about the out-of-plane relaxation of the film during the growth that could not be observed before. Moreover the dependency of the epitaxial order on the potential used for the UPD deposition process was also investigated.

Resume : The use of Pt and Rh metallic and alloy nanoparticles on oxide supports ranges from chemical industry to catalysts in automotive exhaust gas converters. To improve catalyst performance it is essential to grasp the interplay between the particle size/shape, the formed oxides, the support and the catalytic activity. This triggers the need for atomic-scale studies of supported nanoparticles during catalytic reactions under realistic conditions. Here we present our results on MgAl2O4(001)-supported Pt0.33Rh0.67 nanoparticles “at work” during carbon monoxide oxidation at near ambient pressures studied by means of surface x-ray diffraction and in-situ mass spectrometry at beamline P09 at the PETRA III storage ring at DESY. The use of a dedicated in-situ catalysis chamber allowed for the time-resolved monitoring of the formation of surface oxides on the nanoparticle facets, and to correlate it to the sample`s catalytic activity, hence identifying the catalytically most active oxide phase. Furthermore, the combination of high-resolution reciprocal space mapping and high-resolution linescans performed through particle Bragg peaks facilitated the quantitative determination of the activity-induced particle shape and size changes and thus of the particle sintering during reaction conditions.

Resume : Combining semiconductors in heterojunctions appears as one of the most promising ways to improve the performances of devices for solar water splitting (sun light assisted water oxido-reduction for hydrogen production as a clean fuel). However, assembling different materials together results in the existence of interfaces leading to global electronic structure modifications of the stacking. Since the band structure is a key parameter for water splitting, there is a clear need for characterization techniques able to investigate this band structure, and especially to determine it for each material and for the interfaces (presence of defects, potential barriers). A very powerful technique to tackle these issues is Resonant PhotoEmission Spectroscopy (RPES). RPES conditions are fulfilled when we realize XPS using excitation photons of an energy close to the absorption threshold of a core level (previously determined by XAS), which provides (in a simple picture) chemically selective photoemission. It is a useful technique for the investigation of valence band features in solids. Moreover, this technique can be used to investigate the electronic structure of a heterojunction interface to determine the band bending or the charge trapping. In this work, we present results of RPES of the valence band performed on epitaxial TiO2/Ti-doped Fe2O3 heterojunctions. The provided insights concerning the interface and the electronic structure are correlated to water splitting performances.

Resume : Iron oxide nanoparticles find application in different areas like sensing [1], magnetic storage media [2], and biomedicine [3], due to their magnetic properties and environment-friendliness. In the present contribution, we report on the in situ investigation of an iron oxide nanoparticle synthesis by coupled X-ray absorption near-edge structure (XANES) and small-angle X-ray scattering (SAXS).[4] The combination provides simultaneously information about the size of particles (SAXS) and on the oxidation state and the local structure of the iron atoms (XANES). The co-precipitation synthesis was exemplary studied, using a stabilization agent to decelerate the fast precipitation of the iron oxides. This allows to detect intermediates in situ. The measurements were performed using a custom-made acoustic levitator as sample holder. From the data, a mechanism was derived indicating different phases of particle formation and oxidation state changes. References [1] V. Urbanova et al., Chem. Mater. 23 (2014) 6653. [2] S. Sun et al., Science 5460 (2000) 1989. [3] E. Amstad et al., Nanoscale 7 (2011) 2819. [4] A. Kabelitz et al. CrystEngComm 17 (2015) 8463.

Resume : The corrosion protection of aluminum relies in many cases on a thin native oxide formed at ambient conditions or a thicker anodic oxide which can be formed by electrochemical anodization. Whereas the atomic scale structure of annealed aluminum oxides is known from several studies [1], the atomic arrangement of low temperature aluminum oxides, including native and anodic, has been detained due to its complex amorphous structure. A better structural knowledge of these oxides are important for applications as well as for the fundamental understanding of the accuracy of experimental methods commonly used to determine structural properties of such oxides. Previously we have compared the electrochemical oxidation rate using X-Ray Reflectivity (XRR), and Electrochemical Impedance Spectroscopy (EIS) in separate measurements in a 2M Na2SO4 solution [2]. In the present contribution, we have combined XRR and EIS, to study in-situ the anodization in a citrate buffer solution on industrial aluminum alloys as well as on single crystal aluminum surfaces, simultaneously. The measurements were performed at the P08 beamline at PETRA III in Hamburg, and at the ID3 beamline at ESRF in Grenoble. The results show that the stability of the anodic oxides depends on the solution, and that the determined thicknesses differs for XRR and EIS. Further, the results also show that the oxide thickness depends on the substrate. The reasons for the disagreement between XRR and EIS will be discussed as well as the difference in oxidation between alloys and single crystals. References [1] Kresse, G., et al., Science, 2005. 308(5727), 1440 [2] Bertram, F. et al., J. Appl. Phys. 116, 034902 (2014)

Resume : Among families of nanoparticles, oxide nanoparticles synthesised in water are quite peculiar as they tend to form similar morphologies. For instance, titanium oxide, zirconium oxide, zinc oxide, cerium oxide, yttrium vanadate, etc. all seem to be the result of agglomeration of crystalline primary grains. This two-level structuration is not well understood but is the key for understanding oxide syntheses in general, and is obviously vital when intending to optimise the development of functional materials. In the name of understanding the mechanisms of formation of these systems, a model system was chosen: luminescent yttrium vanadate. In this work, an original pathway to obtain YVO4: Eu nanoparticles is explored. The particles are obtained by coprecipitation in water, upon mixing two aqueous precursors. Tuning the pH of the vanadate precursor leads to two different nanostructures: ?classical? polycrystalline particles of 40 nm composed of primary grains of 2 to 5 nm, and monocrystalline-like particles of 40 nm. To explain this difference in structure, in situ and ex situ luminescence and SAXS/WAXS studies were conducted. In particular, we demonstrate that the difference in nanostructure comes from a difference in mechanisms of nucleation and growth, caused by the early intermediate states.

Resume : We report on the fabrication and testing of a novel concept of sealed electrochemical microcell for in situ soft X-ray microspectroscopy in transmission, dedicated for non-vacuum compatible electrolytes. Classical UV lithography and UV-NIL like process have been used to produce electrochemical wet cell, a single solid block based around a microfabricated channel with fixed optical windows and apt for microfluidic work. Moreover, this cell allows to employ an advanced electrodic geometry developed in our group ? so far used only in open electrochemical cells for work with vacuum-compatible electrolytes - also with low-vapor pressure liquids, possibly saturated with the required gases. The cell optimal electrode design allows three-electrode electrochemical control typical of traditional electrochemical experiments. The first electrochemical experiments with this new cell explore the electrochemical growth of a Co-polypyrrole, a composite electrocatalyst material with promising performance to replace the expensive Pt catalyst in fuel-cell oxygen electrodes. Morphological and chemical-state distributions of Co codeposited with polypyrrole has been followed as a function of time and position, yielding unprecedented information on the processes relevant to the synthesis of this catalyst.

Resume : Photoactive TiO2 surfaces based on high density arrays of nanowires present a wetting behavior tunable from superhydrophobic (water repellent) to superhydrophilic (fully wet) regimes. These states are depicted in a reversible way by simply irradiating with ultraviolet light (superhydrophobic to superhydrophilic) and recovered by storage in dark. However, the mechanism responsible for this transition is far to be elucidated. Herein, we present unprecedented in-situ XPS analysis at near ambient pressure performed in CIRCE beamline at ALBA synchrotron facilities for unraveling the wetting behavior of supported photoactive TiO2 nanowires commanding the dropwise to filmwise condensation transition. In-situ environmental microscopic (ESEM) following of the different wetting behavior supports the chemical study. These experiments show crucial information at microscopic and molecular level reflecting the surface wettability and chemical state modifications of these photoactive one-dimensional surfaces, being relevant for industrial applications in which water vapor condensation and surface tension have a critical role such as self cleaning surfaces, antifreezing devices and water harvesting systems.

Resume : Ternary cobalt-magnesium oxide thin films have been deposited using RF-magnetron co-sputtering from metallic targets. The oxidation state of Co was evaluated using the satellite structure of Co2p 3/2 spectra from in-situ XPS measurements. By changing the magnesium content of the films the Co 2 /Co 3 -ratio can be modulated over a wide range. As the Co3d states form the top of the valence band these modulations are also resembled in the density of states at the valence band maximum. Co 3 -rich samples show a single peak at around 0.8 eV whereas Co 2 -rich films exhibit a single peak at around 1.9 eV. For samples with a mixed valency of cobalt a superposition of these peaks is observed. The work function of the thin films was determined using the secondary electron cut-off from in-situ UPS measurements and shows a tendency to increase with increasing Co 3 content. The same trend was observed for the conductivity of the samples which was measured in a four-pointsetup. Structural investigations were performed using XRD and Raman spectroscopy. The density of states at the valence band maximum is further compared to electronic structure calculations.

Resume : Ion-exchanged zeolites play a potentially important role in the capture of greenhouse gases (e.g. CO2) and for the upgrading of biogas and natural gas. Adsorption-based processes are reasonably well established for post-combustion capture of CO2 at point sources and for biogas upgrading. Good adsorbents are essential for these processes. For CO2 removal, the adsorbent should at least have a high capacity for CO2 and high selectivity for CO2 over other gases in the mixture. Zeolite |NaK|-A had previously shown high CO2 selectivity over N2 with good CO2 uptake kinetics. This was attributed to the presence of a K+ ion close to the 8-ring windows. Here, we used diffraction methods to investigate zeolite |NaKCs|-A with certain cation compositions that have shown very high CO2 selectivity over CH4. The high selectivity renders the material potentially a good adsorbent for biogas upgrading. Synchrotron X-ray powder diffraction on beamline ID22 at the ESRF was successfully applied in order to determine the location and occupancy of the non-framework cations. The Cs+ and K + were found to occupy the positions at the 8-ring. We also performed a series of in situ diffraction measurements with zeolite |K|-ZK4 where we studied the position changes of the non-framework cations during CO2 sorption.

Resume : Fe-Cr-Al alloys are an emerging alloy class for fusion energy applications. This is due to Fe-Cr-Al alloys having similar materials performance but improved compatibility with corrosive environments like Pb-Li when compared to Fe-Cr alloys. This work examines the radiation tolerance of Fe-Cr-Al alloys with an emphasis on developing a mechanistic understanding on the role of Al and Cr on the formation of Cr-rich ?' precipitates under neutron irradiation. Model Fe-(10-18)Cr-(2.9-4.9)Al (wt %) alloys were irradiated in the High Flux Isotope Reactor (HFIR) to 0.3-9 dpa between the temperatures of 300-400°C. Irradiation conditions were selected to enable the direct comparison of Fe-Cr-Al results to the rich database on irradiated Fe-Cr alloys. Comprehensive testing and characterization was conducted on the non-irradiated and irradiated specimens with mechanical testing, small angle neutron scattering (SANS), atom probe tomography (APT), and advanced electron microscopy. Results indicate that radiation-induced hardening, represented by a yield strength increase, can be observed in Fe-Cr-Al alloys as high as 350 MPa. Initial structure-property relationships indicate radiation-induced hardening was directly related to the formation of dislocation loops with Burgers vector of a< 100> and a/2< 111> and the precipitation of nanometer scaled Cr-rich ?' under irradiation. Alloy Cr content was found to strongly influence precipitation, a result that mimics findings for Fe-Cr alloys. Al content had little effect on phase stability at the compositions studied. Significant precipitation (?1024 m-3) was found to dominate the hardening response in the Fe-Cr-Al alloys. Damage dose (dpa) and irradiation temperature were also found to influence the size, number density, and composition of Cr-rich ?' precipitates. This presentation will present a detailed analysis on the irradiation performance of Fe-Cr-Al alloys and provide guidance on the development of Fe-Cr-Al alloys for fusion energy applications from the perspective of composition refinement for enhanced radiation tolerance. Research was sponsored by DOE Office of Nuclear Energy, Advanced Fuel Campaign of the Fuel Cycle R&D program. The High Flux Isotope Reactor and beamline CG2 of ORNL was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. We are grateful to Dr. Jeremy Busby for his technical inputs and stimulating discussions.

Resume : Functional oxides posses a variety of properties making them promising for nanoelectronic applications. They cover a broad range of conductivities often combined with magnetic or ferroelectric behavior, or even the coupling between those effects. To name one example, the magnetic oxide EuO belongs to the rare class of ferromagnetic insulators which can be used as a spin filter for spin-based electronic applications. The task of realizing heterostructures of complex oxides and the fine tuning of their properties calls for advanced synthesis and characterization techniques. The challenge of growing single-crystalline and stoichiometric metal oxide films lies in the exact supply of metal and oxygen. In the case of EuO ? a metastable oxide ? any slight deviation from the extremely confined parameter range results in the formation of either Eu or oxygen vacancies, Eu clusters or overoxidized phases. We designed an UHV system based on a MBE chamber optimized for the growth of thin oxide films on various substrates, featuring in situ analysis by XPS and electron diffraction techniques. This unique setup allows us not only to control the structure of thin oxide films but simultaneously their chemical state and thus their functional properties. As a benchmark for our new MBE system, we realized the highest quality synthesis of epitaxial EuO layers on yttria-stabilized zirconia (YSZ). The cubic oxide YSZ is an established substrate for the heteroepitaxial integration with the ferromagnetic oxide EuO. Due to the perfect lattice match of (aYSZ - aEuO)/aEuO = 0.04% and high thermodynamic stability, YSZ (001) is an ideal substrate for studying the structural, chemical, and magnetic properties of ultrathin EuO with outstanding single-crystalline quality. By combining oxide MBE with in situ XPS analysis we are able to fine-tune the stoichiometry of our EuO films without the capping layer usually needed for ex situ analysis.

Resume : Techniques of small-angle scattering (neutrons, X-rays) are known to be versatile tool for studies of structure of solids from atomic scales up to submicrometer ones. Scattering of radiation is universal physical phenomenon and occurs at various inhomogeneities. It is contributed from any structural feature providing a complicated response function which can be decoded resulting in knowledge of different components in a system under study. In the present communication, we consider application of small-angle neutron scattering (SANS) for study of the silicate doped glasses: (1) the glasses doped with semiconductor nanoparticles (PbS and PbSe) and (2) the glasses with metal oxides, CeO2 and TiO2. Both materials are of interest due to unique optical features those are generated through appearance of nanosized and cluster-like species stabilized within the glass matrix. For PbS/Se-doped glasses the SANS study confirmed formation of nanoparticles (size range of 5-10 nm) observed by TEM and XRD within glass, but they are partially aggregated and produce fractal structures together with nearest environment. These features are controlled by the secondary heat treatment of the PbS/Se-doped glasses. In the case of CeO2/TiO2-doped glasses, SANS have allowed reveal complex structure including Ce-Ti-oxide clusters (invisible in TEM) and the larger fractal aggregates with sizes in the range up to 100 nm. Structural features decoded by SANS technique contribute to optical properties and strongly influenced by Ce/Ti composition.

Resume : We will describe several methods for characterization of thin layers, using fast acquistion approaches implemented at DiffAbs beamline. A hybrid pixel area detector and a monochromatic well collimated X-ray beam from a synchrotron are used, combined with a continuous data acquisition mode, in order to perform 3-dimmensional (3D) mapping of the angular / reciprocal space. Several examples of information which can be addressed will be shown: i) texture (orientation) information: is typically observed and quantified by the measurement of so-called pole figures. Several pole figures (one dataset) can be accessed in time intervals as short as one minute, with a gain in measuring time by up to two orders of magnitude with respect to the classical (point detector) approach. ii) X-ray reflectivity: gives easy access to information like thickness, electron density and roughness of thin films (on a substrate). Measurements up to high momentum transfer values (~0.1 nm^-1) can be performed in total time as short as 10 s, possibly extracting background corrected reflectivity and GISAXS signals from the 3D data. The gain can be up to two decades as compared to the classical acquisition scheme (monochromatic X-ray beam, point detector and rocking scans). iii) (wide angle) X-ray diffraction: allows access to informations like lattice parameters, crystalline phases, crystalline orientation, strain, etc. The in situ creation of a diffuse interface during a thermal annealing will be detailed.

Resume : Copper(II) monoxide (CuO) is a prototype compound for high-Tc superconducting cuprates [1] and is well suited to study the charge ordering phenomenon [2] and compressibility of copper-oxygen bonds [1]. It also finds broad range of applications in nanostructured form [3]. Electron-phonon and spin-lattice interactions play an important role in bulk CuO, which has monoclinic structure [4] built up of CuO6 octahedra strongly distorted by the Jahn-Teller effect. High resolution x-ray diffraction measurements [5] from 100 to 1000 K revealed anomalies in the lattice constants appearing at the known antiferromagnetic phase transitions (below 230 K) due to strong spin-lattice coupling. In this study we applied the Cu K-edge x-ray absorption spectroscopy to follow the evolution of the local atomic structure and lattice dynamics in microcrystalline and nanocrystalline CuO as a function of temperature (10-300 K), pressure (0-30 GPa) and size (downto 6 nm). The obtained results will be discussed and interpreted based on the first-principles calculations. [1] H. Ehrenberg, et al., J. Phys.: Condens. Matter 11 (1999) 6501. [2] X.G. Zheng, et al., Phys. Rev. Lett. 85 (2000) 5170. [3] Q. Zhang, et al., Prog. Mater. Sci. 60 (2014) 208. [4] S. Asbrink and A. Waskowska, J. Phys.: Condens. Matter 3 (1991) 8173. [5] H. Yamada, et al., Phys Rev. B 69 (2004) 104104.

Resume : In this paper, we propose a new approach to the identification and structural analysis of Nanophase metal clusters in liquid metals as an example molten aluminum. We investigated the processes of growth and metal nanostructures self-organization and effective control ways of the structure and materials properties at the nanoscale. This work is based on the results of earlier studies [1, 2] on the existence of Al melt clusters (nanoscale regions), preserving the symmetry of short-range order, were seen as a source of acoustic emission (AE) signals. In this paper we made Fourier analysis of AE signals generated by the melt at 840°C and the crystallization point. The experimental data allow to examine structural changes in the dynamics of the melt during the entire investigated temperature range. There are clusters with two lattice modifications in the phase formation. The process of solid phase formation consists of two steps with the change of a crystal lattice. We experimentally obtained patterns of change in the number and energy of AE signals at melt temperature (860°C) and crystallization point. The results of spectral analysis are analyzed in the framework of the cluster theory melts. [1] V. Vorontsov, D. Zhuravlev, A. Cherepanov, Experimantal study of the structural characteristics of Al melts on the basis of Fourier analysis of acoustic emission signals, Journal of Crystal Growth 401 (2014), 124-127 [2] V.B. Vorontsov, D.Zhuravlev, J. Chem. Eng. 6 (2012), 358-362

Resume : The newly developed EXAFS set-up comprises both time- and spatially-resolved EXAFS information simultaneously in a single-shot. This facile, stable and scanningless set-up was tested at the BAMline @ BESSY-II (Berlin, Germany). The primary broadband beam is generated by a filter/X-ray-mirror combination (bandpass). The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by an area sensitive detector based on a CCD camera, in a theta - 2theta geometry [1]. The first in situ measurements were successfully carried out and hereby presented. We were able to track structural changes within a 1s time resolution. References [1] A. Guilherme Buzanich, M. Radtke, U. Reinholz, H. Riesemeier, F. Emmerling. Time- & spatial-resolved X-ray absorption fine structure (XAFS) spectroscopy in a single-shot ? new analytical possibilities for in situ material characterization. Submitted to JSR (2016).

Resume : CuAgZr alloy has been remarkably known for good compromise between high strength and high conductivity. The strengthening is mainly contributed by the self-aligned nanosize Ag precipitate on {111} planes in the Cu matrix. In this study, the evolution of Ag precipitate in Cu-7wt%Ag-0.05wt%Zr during thermal processing is characterized to control the alloy microstructures and thus improve its mechanical strength and electrical conductivity. The solution treated CuAgZr alloy samples were cold rolled with logarithmic strain of 2.3 and subsequently aged with various times. The complementary small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) techniques indicate the evolution of precipitate size distribution during different thermal routines and clarify that the change of dislocation density has a direct effect on Ag precipitation coarsening and Ag precipitate distributions. This paper discusses correlation between the effect of plastic deformation and the evolution of nanoscale Ag precipitate.

Resume : Adsorptions of CO2 on neutral and positive charges of spin–polarized Cu–doped on oxygen vacancy defect on anatase TiO2 (001) (denoted Cu/[TiO2+Vo]) surface were found and their adsorption energies are reported. Mechanism for CO2 adsorbed on the neutral and positive surfaces of spin–polarized of the Cu/[TiO2+Vo] surface and its conversion to CO were investigated. The Cu/[TiO2+Vo] surface modeled as 25% copper loading of which atoms are homogeneously distributed over the [TiO2+Vo] was chosen. Bindings of Cu atom onto neutral and positive charged [TiO2+Vo] at spin–polarized surface state were investigated and their binding energies are reported.

Resume : InxGa1-xAs/GaAs structures, grown by metalorganic vapor phase epitaxy (MOVPE) at 520°C, were investigated by in situ spectral reflectance (SR), high resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM). HRXRD curves are analyzed to determine the indium composition of different samples, denoted A, B, C, D and E. Reflectance three-dimensional plot as function of time and wavelength was recorded to quantify the evolution of reflectivity in the wavelength range from 400 to 1000 nm and to determine some growth parameters such us growth rates and thicknesses of InxGa1-xAs layers. Longitudinal cut through the 3D plot shows dissimilar behavior of reflectivity temporal evolution in three regions: region I (400-560 nm), region II (560-750 nm) and region III (750-1000 nm). Best simulations of reflectivity signals using the transfer matrix method (TMM) are developed to analysis the variation of optical constants spectra and the sensitivity (σSR) of incident wavelength to surface morphology of InxGa1-xAs layers. The obtained values of σSR were compared to RMS surface roughness given by AFM. A good agreement between the experimental results and the theoretical predictions was found. Keywords: InxGa1-xAs/GaAs structures; In situ spectral reflectance; refractive index; Atomic force microscopy; MOVPE. *Corresponding Author: mohamedmourad.habchi@fsm.rnu.tn

Resume : The capabilities offered at modern large scale facilities (synchrotrons) together with advanced techniques like the atomic Pair Distribution Function (PDF), provide unique tools needed to unveil the nanoscale structure of complex crystalline materials. In the present work a core-shell iron oxide nanoparticle (IONP) system is being studied by X-ray total scattering in a wide temperature range. We uncover its peculiarity mainly due interfaces grown between structurally dissimilar ferrimagnetic and antiferromagnetic phases, coexisting in the same nanoscale building block. Consequently interface-driven exchange coupled phenomena determine the bulk magnetic behaviour of the nanoparticle system and facilitate its technological exploitation. Knowing the extent of the interfaces, as much as the volumetric ratio of the magnetic phases from transmission electron microscopy, and being able to determine the local anisotropy associated with nanostructural distortions are proved to be the key for the interpretation of our magnetic measurements. Synchrotron X-ray PDF results (at XPD-1, NSLS-II) indicate that the local structure differentiates among nanoparticles with tailored morphology (size: 8-18 nm; shape: spherical, cubic). We demonstrate the atomic structure evolution of IONPs when their morphology is modified, while we also discuss the possible correlation between structural transformations and magnetic transitions, and finally suggest ways to chemically tune their magnetic response.

Resume : A densely packed self-assembled stearic acid monolayer was fabricated by solution deposition on single-crystal C-plane aluminum oxide (sapphire) that was pre-annealed at 1500°C for 3 h in a muffle furnace. The thermal desorption with increasing temperature was investigated by atomic force microscopy(AFM), X-ray photoelectron spectroscopy(XPS), and contact angle(CA) measurements. The AFM results revealed that the surface coverage remains unchanged in air until the temperature is increased up to ~80°C, and then, it decreases with increasing temperature, before becoming zero at 220°C. In addition, even below 110°C, desorption species are the molecules which is physical adsorption that confirmed by the XPS tests. Further, XPS and contact angle results indicate that at temperatures above 140°C, desorption of hydrocarbon fragments formed by cleavage of the alkyl chains of stearic acid molecules occurs, but the carboxylic acid head group remains on the surface even at 220°C when the surface coverage is zero.

Resume : Transparent and conductive oxides thin films, such as indium tin oxide (ITO), were deposited on glass substrates by radio frequency magnetron sputtering technique with different thicknesses (0.5 µm - 0.7 µm). The obtained samples were structurally (XRD, SEM and AFM), optically (transmission spectra) and electrically (I?V characteristic) characterized. These ITO films have been found to be by AFM investigations smooth, uniform and with a surface roughness smaller than 10 nm on small surfaces. Using X-ray diffraction, we could determine that all samples were polycrystalline. The grain sizes of the films estimated from the (222) reflection have been found to increase with the film thickness from X to Y nm. The optical properties, evaluated by UV-VIS-NIR (190-3000 nm) spectrophotometer, showed that the obtained thin films were highly transparent, with a transmission coefficient between 90 ? 96 %, depending on the film thickness. Optical properties of these oxide films in near infrared (NIR) range were described by the Drude free electron model. A computational algorithm for oxides films using computational models was developed and optical properties were investigated (the Swanepoel and Wemple DiDomenico model). These oxide layers present interesting optoelectronic properties in terms of basic research and related applications of plasmonic metamaterials.

Resume : The process of electroless plating Ni-P and Ni-P/nano-SiO2 on API-5L X65 carbon steels was improved. The Ni-P/nano-SiO2 composite coatings were prepared from the baths containing different concentrations of nano-SiO2 particles. The coatings' surface and morphologies were observed via scanning electron microscopy (SEM). The chemical compositions were analyzed by EDAX. The corrosion behaviors were evaluated by electrochemical impedance spectroscopy tests. The experimental results indicated that SiO2 nano-particles co-deposited but some agglomeration occurred. Micro-hardness of electroless Ni–P–SiO2 composite coatings increased due to the existence of nano-particles. Corrosion tests showed that both electroless Ni-P and Ni-P/nano-SiO2 composite coatings demonstrated significant improvement of corrosion resistance of substrate in salty atmosphere and latter coating type appeared to offer a better corrosion protection.

Resume : Multiferroic materials are expected to lead to many applications in the field of spintronics. Among them, ferrimagnetic CoFe2O4 spinel thin layers on ferroelectric BaTiO3 constitute a well referenced system for the study of multiferroic coupling. The physical mechanisms underlying this coupling yield some controversies. Its direct or indirect nature remains to be elucidated in details. The coupling is considered indirect if mediated through strain. Disentangling direct and indirect coupling is a challenging task that requires studying magnetic, electric and structural aspects of the same system. In the present work we focused on the different strategies to investigate magnetoelectric coupling combining PiezoForce Microscopy (PFM), X-ray Magnetic Dichroism (XMCD) and surface X-ray diffraction (SXRD) and X-PEEM techniques at synchrotron SOLEIL and DIAMOND light source. For the purpose of this study, numerous thin-layered epitaxial samples of CoFe2O4 (2.2 - 15 nm range) / BaTiO3 (3 - 21 nm range), elaborated by atomic oxygen plasma assisted molecular beam epitaxy, were prepared. Combining XMCD and SXRD results show that strain modifications are strongly correlated to the evolution of the MR / MS ratio (MR magnetic remanent moment, MS saturation moment). Additional PFM writing of patterns on the sample surfaces, using different tip voltages show film thickness, and thus strain, dependences that stress the existence of an indirect magnetoelectric coupling. Spectromicroscopy inves

Resume : Self assembled monolayer (SAM) derived from aminohexyl phosphonic acid (AHP) as protective nanolayer on iron surface have been characterized by contact angle measurements, scanning electron microscopy and in situ electrochemical quartz crystal microbalance (EQCM) techniques. SAM formation and growth processes were monitored by EQCM technique and the step by step construction was investigated through quantification of the mass variation corresponding to adsorption of nanolayer onto iron surface via phosphonate terminated groups of molecules. All measurements suggest that AHP molecules can spontaneously adsorb onto the iron surface to form an oriented monolayer, which improve the hydrophobic character of surface. Corrosion protection ability of AHP/SAM against the acidic corrosion of iron was also evaluated in 0.1 M H2SO4 solution using EQCM and potentiometric polarization techniques. Electrochemical measurements indicate that significant decrease in the corrosion rate of iron was observed in the presence of AHP/SAM and surface blocking property of adsorbed layer is the function of immersion time. Polarization data reveal that AHP/SAM acts as mixed type inhibitor and corrosion inhibition might have been due to Fe-AHP complex formation by adsorption of AHP onto iron surface. Quantum chemical calculations showed that AHP has relatively small E between HOMO and LUMO and large negative charge of phosphonate group, which facilitate formation of a Fe-AHP complex on iron surface.

Resume : Unique properties of boron doped nanodiamond (BDND) provide promising applications for it in nanotechnologies, electronics and biomedicine. This study is devoted to investigation of influence of BDND and detonated nanodiamond (DND) modified by COOH groups on hydrogen bonds in water and water-ethanol solvents with weak, medium and strong hydrogen bonds using IR and Raman spectroscopies. As a research object, the novel sample of BDND (with the size 11 nm) synthesized by HTHP method was used. The analysis of temperature dependences of the quantitative parameters of valence bands of OH groups of the solvents and the NDs suspensions has shown that BDND and DND differently weaken the hydrogen bonds in water and in water-ethanol solution with 70 vol. % ethanol content when samples are heated. In water-ethanol solution with 20 vol. % of ethanol, in which the hydrogen bonds are the strongest, both NDs practically do not change the hydrogen bonds network. On the base of the obtained results, the mechanisms of BDND and DND influence on the connectivity of solvents molecules were proposed.

Resume : Through first principles calculations, the optical properties, spontaneous polarization and the effective mass of the cubic perovskite BaHfO3 under pressure effect have been investigated, using the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method implemented in the WIEN2K code, in connection with the Generalized Gradient Approximation (GGA). During this study, the effect of pressure is seen on the electronic and optical properties such as: The band gap value (Eg) of the perovskite BaHfO3 is reduced and it becomes indirect instead of direct band gap as pressure increased. From the band structure we have also computed the variation of effective masse (m*) which increases to the same effect as the pressure. The results of the optical study, shows that the absorption coefficient increases and the spontaneous polarization (Ps) increases in a quasi-linear behavior as pressure increases.

Resume : We have been studying nano particle generation under atmospheric pressure discharge environment. Plasma-chemical applications for nano particle production in atmospheric pressure require high electron temperature, density and low gas temperature. However, no conventional thermal plasma or non-thermal plasma can satisfy these conditions simultaneously. One of the candidates to create mixture state of thermal and non-thermal plasma is gliding arc discharge. The gliding arc discharge starts from arc at the shortest gap between two divergent electrodes and it glides along gas flow. The arc cannot maintain when the length of the arc exceeds its critical length and transition from thermal to non-thermal plasma occurs. This transitional discharge is very attractive but is non-uniform in time and space. We have focused on compressional wave generated by discharge because it includes information about discharge current and atmospheric condition around discharge. A condenser microphone has been used to detect audible discharge sound wave, however it is impossible to set it close position to discharge electrodes where electric field is very strong. On the other hand, optical measurements such as beam deflection, Shadowgraph and Schlieren have been employed to avoid the above mentioned problem of a microphone. Relationship between discharge current and sound during gliding arc discharge was focused in this work. Measurement and analysis of waveforms of applied voltage, discharge current and discharge sound were carried out. A new technique of optical wave microphone was introduced to observe generation of compressional wave after one pulsed discharge in air.

Resume : During water desalination or oil production, the precipitation of calcium sulfate (primarily gypsum, CaSO4.2H2O) scales leads to costly problems including pipeline or membrane clogging. The use of inhibitors is a promising approach to mitigate scaling. However, standard additives are often environmentally harmful and it is therefore paramount to find, test and validate more biodegradable, green alternatives. Here we present data from a study where we followed the nucleation and growth kinetics of gypsum crystals in the absence and presence of two green inhibitors polyepoxysuccinic acid (PESA) and polyaspartic acid (PASP). Reactions were monitored for up to four hours by measuring changes in turbidity using UV-VIS spectroscopy. The mineralogy, morphologies and surface properties of the solid end products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). UV-VIS results indicate a clear interdependence between additive concentration, additive type and crystal growth kinetics. In the absence of additives, the turbidity started increasing after 2 minutes, but the presence of 20 ppm PESA or PASP increased the induction time 6 and 9 times, respectively and they both decreased the rate of crystallization decreased. XRD showed that all end products to be gypsum and SEM images revealed that in the presence of PESA and PASP the usual long needle shaped gypsum crystals became significantly shorter indicating a shape modification effect. XPS results suggest that this may be due to surface adsorption of the additives onto the growing gypsum crystals.

Resume : DESY NanoLab provides access to advanced nano-structuring, nano-synthesis and nano-characterization techniques complementary to the X-ray light sources available at DESY. The DESY NanoLab is being developed and operated by the DESY Research Group X-ray Physics and Nanoscience as facility for users and for in-house research. The scientific instrumentation of the DESY NanoLab comprises an ultrahigh vacuum (UHV) setup for surface preparation and nanoparticle growth with surface science techniques, including X-ray photoemission spectroscopy (XPS), reflection-absorption infrared spectroscopy (UHV-RAIRS), and scanning tunnelling and atomic force microscopy (UHV-STM/AFM). In addition, an X-ray diffraction laboratory houses two hutches for determining specular reflectivity and grazing incidence X-ray diffraction measurements, and to map the full reciprocal space. Both hutches provide sufficient space to mount various mobile sample environments for catalysis, high temperature or electrochemistry for in-situ analysis. Additionally, DESY NanoLab operates a high resolution field emission scanning electron microscope (FE-SEM) and a dual beam focused ion beam instrument (FIB) for cross section sample preparation, 3D micro-tomography, and nano-manipulation. Electron and ion-beam assisted deposition of Pt permits to write markers close to pre-selected nano-objects, which are used for re-localizing the nano-objects at the nanofocused X-ray beamlines at DESY, exploiting the X-ray fluorescence and an advanced protocol for transfer and positioning. For more detailed information, see the DESY NanoLab-website at: http://photon-science.desy.de/research/research_teams/x_ray_physics_and_nanoscience/desy_nanolab/

Resume : NFFA-Europe integrates 20 partners half of which are nano-foundries co-located with Analytical Large Scale Facilities (ALSFs). The project funded by the European union covers i) Transnational Access (TA) activities performed at nano-laboratories and ALSFs and providing the opportunity to support comprehensive projects for multidisciplinary research at the nanoscale integrating theory and numerical analysis, structural and morphological characterization, electronic and chemical characterization, and magnetic, optical and electric characterization; ii) Networking Activities (NAs) designed and organized to foster an effective interface with the wide-ranging user communities and making experimental data suitable for industrial exploitation; and iii) Joint Research Activities (JRAs) aiming to develop methods and tools at the frontier in nanoscience research and feeding back into an improved offer of the research infrastructure to carry out academic as well as industrial projects. Proposal submission is possible via a single entry point (SEP) web-portal with assistance from the Technical Liaison Network (TLNet). An access management structure is ensuring optimized service provision to users guaranteeing scientific excellence and innovation of the selected proposals. For more detailed information, see the NFFA-website at: http://www.nffa.eu/

Resume : The crystallization of NiTiCu/Ni-rich multi-layer nano-glass thin films deposited by magnetron sputtering was investigated. The multi-layer thin films deposited at room temperature with amorphous structure were annealed at 773 K for 15, 30, and 60 min for crystallization. Grazing incidence X-ray diffraction (GIXRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) were used to study the structure and interface of the thin films. The chemical composition gradient of the bi-layer after annealing was determined using secondary ion mass spectroscopy (SIMS). The results show that the structure of the annealed thin films and interface between them strongly depends on the temperature and time of the annealing. The as-deposited thin films are fully amorphous as they exhibit broad diffraction peaks characteristic for glassy state. In the plain view by SEM and TEM, a globular nano structure appears with boundaries of few nanometers. HRTEM images show that the sputtered layers are totally amorphous. No long range periodic lattice was observed and the interface between layers is flat and sharp. After annealing for 15 min, the NiTiCu was partially crystallized but the NiTi layer has an amorphous structure. Three zones are observed in the NiTiCu layer. The first zone is just above the interface has amorphous structure and then, there is a precipitate free zone (PFZ). The presence of vacancies in the amorphous structures encourages the formation of the precipitates but close to the interface, the vacancies can be absorbed by the interface and reduction of the vacancies concentration delays precipitation formation, cause to form the PFZ. The third zone partially crystallized and contains nano-precipitates supposedly Ti-rich. After 30 min annealing, the NiTi layer is partially crystallized as well and the interface between layers contains highly mixed quasicrystal nano-particles and an amorphous phase. After 60 min annealing, both of the layers were fully crystallized with the different structure and because of diffusion of the elements through the interface and a full diffused interface was formed. The chemical composition profiles show that there is a compositional gradient in the multi-layer which leads to gradual changes in microstructure through the thickness.

Resume : Hybrid solar cells are produced by applying a water-based processing method [1]. The active layer consists of titanium dioxide nanoparticles produced by laser ablation in liquid and the water-soluble hole-conducting polymer poly[3-(potassium-6-hexanoate)thiophene-2,5-diyl] (P3P6T). Our approach is environment-friendly in processing, and no further high temperature steps are needed. The production of titanium dioxide nanoparticles via laser ablation in liquid is achieved with two basic approaches: titanium dioxide powder as source material and a solid pure titanium target. The produced hybrid solar cells show high fill factors and open circuit voltages underlining the potential of the novel material. A key factor for the performance of the active layer is the functionalization of the nanoparticles with the polymer P3P6T, which is probed spectroscopically. Furthermore the morphology of the active layer is of major importance for the performance of these devices. We used spray-coating as it is a technique suitable for the large-scale and cost-effective preparation. We followed the development of the morphology of the active layer in situ with high spatial and temporal resolution. The mesoscale was probed with GISAXS and the crystallinity of the polymer and the inorganic component was probed with GIWAXS. The changes of the morphology of the active layer are discussed and implications for an improved processing of devices are given. [1] Körstgens et al., Nanoscale 7, 2900 (2015).

Resume : We present new insights in the field of metal oxide films used for solar water splitting derived from the unique possibilities of synchrotron-based characterization techniques. In the solar water splitting process, electron-hole pairs, generated in illuminated semiconductors, realize at their surface the water oxido-reduction reactions (oxygen production at the photoanode and hydrogen production at the photocathode). Photoanodes using hematite (α-Fe2O3) thin films were elaborated by atomic oxygen molecular beam epitaxy and studied using synchrotron-based techniques. Our results take advantage of the capabilities offered by the following techniques for the study of such systems: X-ray Absorption Spectroscopy (XAS), Extended X-ray Absorption Fine Structure (EXAFS), Resonant PhotoEmission Spectroscopy (RPES) and X-ray PhotoEmitted Electron Microscopy (X-PEEM). On the one hand, the interplay between stoichiometry and crystallographic structure was studied by EXAFS for both undoped and Ti-doped hematite films [1,2]. On the other hand, RPES and X-PEEM, together with XAS, revealed how a partial surface chemical etching of Ti-doped hematite improves the photocurrent [3]. For each system studied, we correlated the informations provided by the synchrotron-based techniques with the water splitting performances. [1] M. Rioult et al., J. Phys. Chem. C, submitted (2016). [2] H. Magnan et al., Appl. Phys. Lett. 101, 133908 (2012). [3] M. Rioult et al., Surface Science 641, 310 (2015).

Resume : The lanthanum-based materials, due to their layered structure and f-electron configuration are relevant for electrochemical application. Particularly, La2O2CO3 shows a prominent chemoresistive response to CO2. We compare the high-energy resolution fluorescence detected (HERFD) X-ray absorption spectroscopy (XAS) and valence to core X-ray emission spectroscopy (vtc XES) spectra of series of pure and mixed lanthanide compounds: PrXLa1-X(OH)3, and PrXLa1-XO2CO3, where x is between 0 and 0.1. We interpret the spectral changes based on FEFF9 calculations. The utilization of high-energy resolution Johann-type spectrometers, with the instrumental energy broadening smaller than the core-hole lifetime and low peak-to-background ratio, allows recording spectra of highly overlapping Pr and La L3-edges of the mixed compounds and resolving the 2p to 4f quadrupole transitions in the pre edge region. Moreover, the high sensitivity to subtle changes of the whiteline intensities given by the HERFD method allows us to in situ study the interaction of La2O2CO3 with CO2. Here, we study La2O2CO3-based sensors in operando conditions, at 250 °C in the presence of oxygen and water vapors. We identify that the distribution of unoccupied and occupied states changes during CO2 chemoresistive sensing of La2O2CO3. Finally, we propose a sensing mechanism from resistance measurements and the spectroscopic results.(1 ) (1) Hirsch, O., et al., Proc. Natl. Acad. Sci. U. S. A. 2015, 112, 15803-15808.

Resume : The development of functional materials by taking advantage of the physical properties of nanoparticles needs an optimal control over their size and crystal quality. In this context, the synthesis of crystalline oxide nanoparticles in water at room temperature is a versatile and industrially appealing process, but lacks control especially for “large” nanoparticles (> 30 nanometres), which commonly consist of agglomerates of smaller crystalline primary grains. Improvement of these syntheses is hampered by the lack of knowledge on possible intermediate, non-crystalline stages, although their critical importance has already been outlined in crystallisation processes. Here, we combine time-resolved, in situ SAXS/WAXS and EXAFS to demonstrate that during the synthesis of luminescent Eu-doped YVO4 nanoparticles, a transient amorphous network forms with a two-level structuration. These two pre-structuration scales constrain topologically the nucleation of the nanometre-sized crystalline primary grains within the amorphous network, and their aggregation in nanoparticles, respectively. The amorphous network, which forms within 40 ms, therefore determines the nanocrystalline structure, which forms in the minute range. This template effect not only clarifies why the crystal size is found independent of the nucleation rate, in contradiction with the classical nucleation theory, but also supports the possibility to control the final nanostructure with the amorphous phase.

Resume : Perovskite-type mixed ionic and electronic conductors are highly attractive functional materials with a wide range of applications in present and future electrochemical devices such as solid oxide fuel and electrolysis cells, gas separation membranes and membrane reactors. In this study, model-composite perovskite electrodes were electrochemically polarized at elevated temperatures in O2 as well H2/H2O atmospheres. The polarization induced evolution of surface and bulk properties of the thin film electrodes was monitored in-situ by synchrotron-based XPS and XRD experiments. Electrochemical polarization in O2 led to XPS binding energy shifts of different cations. These shifts are discussed in the light of defect chemical changes of the electrode, which is supported by XRD results showing chemical lattice expansion. In H2/H2O applied bias had strong effects on the composition and valence states of near surface cations. On La0.6Sr0.4FeO3-? cathodic polarization caused the evolution of a metallic iron species on the electrode surface, accompanied by a strong decrease of the polarization resistance for the water splitting reaction. In XRD experiments the metallic iron species was identified as ?-Fe. After retracting the applied voltage the exsolved iron was immediately re-oxidized and the high water splitting activity disappeared. These results clearly identify the exsolved metallic particles as catalytically active for the electrochemical water splitting reaction and yields new insights in the search for novel electrolysis electrode materials.

Resume : ?- and ?-Sn are two stable phases of Sn. ?-Sn is a quasi zero bandgap semiconductor and stable below 13°C. Above this temperature, the BCS-type superconductor ?-Sn is the stable phase. The ?- to ?-Sn phase transition is a prototype of a vibrational entropy-driven phase transformation and serves as a model system to better understand the role of phonons in these transitions [1]. Nuclear inelastic scattering (NIS), an isotope-sensitive synchrotron based technique is an excellent way to directly extract the phonon density of states (PDOS) [2], and from it the vibrational properties of a sample. ?-Sn thin films have been grown using a Knudsen cell and the PDOS was measured in situ using NIS at the ID-18 beamline of the European Synchrotron Radiation Facility. An increase of the ?- to ?-Sn phase transition temperature from 160°C to 180°C was found when decreasing the sample thickness from 20 nm to 10 nm, in perfect agreement with the theoretical model based on the Matthews approximation [3]. Additionally the free energy as a function of temperature for the nanoscale samples was compared to ab initio calculations for bulk Sn in the ?- and ?-phase. This comparison elucidates the interplay between the vibrational behaviour of the thin film and the stabilizing influence of the substrate. [1] B. Fultz, Prog. Mater. Sci. 55 (4), 247?352 (2010) [2] S. Couet et al., Phys. Rev. B 88, 045437 (2013) [3] J. W. Matthews et al., J. Vac. Sci. Technol. 12, 126-133 (1975)

Resume : The low temperature synthesis of nanostructured oxides in an aqueous medium is a topic of great interest from the environmental point of view. Among metal oxides, manganites (MxMnyOz; M = transition or alkali metal) are endowed with interesting magnetic, electrical and catalytic properties. In this framework, zinc (ZnMnO3) and copper (CuMnO2) manganites were synthesised through an easy, reproducible and low-temperature hydrothermal route starting from an aqueous suspension of coprecipitated metal oxalates, and no further thermal treatment or purification were needed. In order to achieve maximum energy-efficiency, we investigate the influence of time and temperature of the thermal treatment on the phase crystallinity and purity. The thorough characterisation of the obtained materials was accomplished by a combined approach of structural and spectroscopic methods, in part based on the use of synchrotron radiation. In particular, the structure of the compounds was investigated at the long- and short-range order by the combined use of XRD and XAS. These analyses yielded evidence of zinc deficiency in cubic spinel ZnMnO3. Furthermore, XPS and XAS revealed the presence of different Mn oxidation states on the surface and in the bulk, respectively, and allowed to determine the local Mn structure. Synchrotron-based time-resolved SAXS experiments were also performed under heating in order to study the crystallization mechanism of the manganites under simulated hydrothermal conditions.

Resume : The deposition of metal layers on silicon is crucial for different aspects of the Si-based semiconductor industry, including the silicide formation for CMOS devices. For molybdenum, a very interesting behavior was found. Below a critical thickness, an amorphous Mo layer formed on top of a MoSi2 interface layer, while for thicker layers the metal film was crystalline over its entire thickness [1]. In the case of MoSi alloys, the critical thickness for the amorphous-to-crystalline transition can be controlled by the Si content [2]. Real-time approaches such as in situ stress measurements and ellipsometry evidenced the transition, but its nature could only indirectly be related to the microstructure of the coatings. The here presented in situ experiments performed at the MPI beamline of the synchrotron radiation source ANKA (Karlsruhe) overcome this problem. Three in situ methods were combined simultaneously during magnetron sputtering co-deposition of MoSi: multiple-beam optical stress measurements (MOSS), X-ray reflectivity (XRR), and X-ray diffraction (XRD) measurements. This unique methodology allows to directly link the time-dependent film thickness and roughness [3] and the stress development [1], with the crystal formation. [1] S. Bajt, D. G. Stearns, and P. A. Kearney, J. Appl. Phys. 90 (2001), 1017 [2] A. Fillon, G. Abadias, A. Michel et al., PRL 104 (2010), 096101 [3] M. Kaufholz, B. Krause, S. Kotapati et al, J. Synchrotron Rad. 22 (2015), 76

Resume : Inorganic and organic thin films are at the basis of many (opto-) electronic devices so that the production of high quality crystalline layers is of high technological importance. Also from a fundamental physics perspective thin film growth exhibits an intriguing interplay of energetics and non-equilibrium kinetics, and in situ and real-time x-ray measurements are well suited to observe the many simultaneous processes in growth, such as nucleation, intra- and interlayer diffusion. Here we show how simultaneous GISAXS and X-ray growth oscillation measurements during growth of the molecular semiconductor PTCDI-C8 (performed at PETRA III) can be used to follow the atomic scale film morphology. This enables us to rule out the often applied diffusion limited aggregation model in favour of attachment limited growth. Importantly, from the in situ data we can infer ways to improve e.g. the film smoothness by growing not at a constant temperature but repeatedly controlling cluster nucleation and island coalescence stages using optimum temperature profiles for each single monolayer. In situ measurements (at ESRF) make it possible to modulate at just the right moment in time and prove that indeed nucleation can be controlled and film roughness decreased. Beyond temperature modulation, laser heating of certain molecule classes in the film can also be used as a novel control parameter in molecular thin film growth. We show how light can texture the thin film crystal structure along the light polarisation and also increase the phase purity. This shows that in situ synchrotron X-ray observation is an invaluable tool to understand growth processes and to find new control variables to alter those nanoscale processes for a tailored thin film structure.

Resume : Tailoring functional nanomaterials is crucial for designing materials on the nanoscale in the field of energy and environment, such as organic photovoltaic cells, flexible electronics and sensors. Their functioning relies on the ability to nanostructure the thin film and the metal-polymer interface [1]. Here, vacuum deposition of metal layers offers a versatile route for fabricating metal arrays, ranging from isolated nanoparticles to full scale electrical contacts. The interaction of the metal atoms with the underlying polymer templates as well as the relevant deposition conditions (e.g. deposition angle, deposition rate and bias-voltage) all play a crucial role and influence both the metal layer growth and the development of the near-surface interface in the polymer-metal nanocomposite. We observe in-situ and in real-time the metal layer fabrication during sputter deposition on polymer templates, combining advanced, high-speed synchrotron-based microfocus x-ray scattering (µGISAXS) and optical ellipsometry. Thus, we correlate the metal layers? structural and morphological characteristics with their optical properties. [1] Roth et al., ACS. Appl. Mater. Interfaces 7, 12470 (2015)

Resume : Great interest has arisen regarding the formation of metastable group-IV elements polytypes due to their fundamental and technological relevance 1. Bulk crystalline germanium is known to exhibit various allotropic phase transitions depending on the pressure and the temperature 2, 3. In particular, the 2H structure is achieved by a thermally activated and stress-induced phase transformation; several (P, T) pathways leading to the Ge-2H phase have been reported in the literature 4. Recently, the HETERNA team (IEF) has demonstrated an original method to induce this phase transformation in nanowires. <111>-oriented Ge nanowires with standard diamond structure (3C) undergo plastic deformation under external stress leading to a phase transformation toward the hexagonal 2H-allotrope. The phase transformation is made possible by embedding the nanowires in hydrogen silsesquioxane (HSQ) resist and baking the sample above 400°C. The resulting nanostructures exhibit Ge-2H nano-domains heterogeneously distributed along their length 5. In order to probe the physical properties of the Ge-2H phase, mid/far IR spectroscopy and µRaman characterizations have been performed. The Raman signal on heterostructured 3C/2H nanowires exhibit a singular band at 287 cm-1 assigned to the E2g Raman mode of the hexagonal diamond phase. IR absorption spectra were collected in the far and mid region on unmodified and heterostructured nanowires. Preliminary data were collected to characterize the chemical and structural changes in HSQ resist during thermal curing. The spectra constitute the background signal of the global spectra acquired on heterostructured Ge nanowires. Additionally, in situ far–IR transmission measurements were carried out on bulk Ge as a function of pressure and temperature. The experiments were implemented at the Synchrotron SOLEIL Laboratory using a designed diamond anvil cell. Results evidence clear IR bands modifications that might be attributed to the phase transitions occurring during the various (P, T) stages. References [1] Brad D. Malone and Marvin L. Cohen, Phys. Rev. B 2012, 86, pp054101 [2] Y. K. Vohra, K. E. Brister, S. Desgreniers, A. L. Ruoff, K. J. Chang, M. L. Cohen, Phys. Rev. Lett. 1986, 56, pp1944. [3] Y. Gogotsi, V. Domnich, High Pressure Surface Science and Engineering, Taylor & Francis: Philadelphia 2003, PA. [4] B. Haberl, M. Guthrie, B. D. Malone, J. S. Smith, S. V. Sinogeikin, M. L. Cohen, J. S. Williams, G. Shen, J. E. Bradby, Phys. Rev. B 2014, 89, pp144111 [5] L. Vincent, G. Patriarche, G. Hallais, C. Renard, C. Gardès, D. Troadec, D. Bouchier, Nanoletters 2014, 14, pp4828

Resume : Self-assembly of anisotropic nanoparticles into mesocrystals is a promising strategy for production and design of nanostructured materials with tunable direction-dependent properties. The non-spherical building blocks and their dynamical, complex formation process require instrumentation and experimental design that account for both the atomic and mesoscopic length scale. We used time-resolved small angle X-ray scattering (SAXS) to follow the evaporation-mediated self-assembly of toluene dispersed iron oxide nanocubes with an edge length of 10.4 ± 0.5 nm. The presented approach of levitating colloidal droplets in an acoustic field enables substrate-free analysis of the assembly process. Our findings suggest a two-step formation mechanism of mesocrystals by combining in-situ SAXS data with ex-situ scanning and transmission electron microscopy. The initially monodisperse, non-interacting nanoparticles agglomerate in the first step. Comparison of a fitted interaction potential to the SAXS data with calculated van der Waals forces suggests the existence of dense packed, disordered assemblies. The second step involves the transformation of the agglomerates into highly ordered domains and subsequent growth into mesocrystals with primitive cubic structure follows the Avrami equation. The mesocrystalline order of the nanoparticles is confirmed by structural analysis of pyrolyzed fragments of the dried droplets with scanning electron microscopy and selected area electron diffraction.

Resume : Intensely and broadly absorbing nanoparticles (IBANs) of silver, protected by aryl-thiol-ligands, are a new class of nanometric, atomically monodisperse superatoms complexes with molecular formula Ag44(SR)30. They are characterized by a large optical cross section, much higher respect to conventional organic dyes and inorganic nano-objects. IBANs feature an unique combination of bulk-like and molecular properties, halfway between small inorganic molecules and larger monolayer-protected metal nanoparticles (radius ? 2nm). IBAN self-assembly forms highly ordered super-structures with a wide absorption spectrum spanning from 380 nm to 850 nm[1]. However, their application in bioscience, nanophotonics, nanoelectronics and light-harvesting [1-3] is limited by thermal stability. Here, we study IBAN functionalized with 4-fluorothiophenol (4FTP) ligand which self-assemblies to form highly ordered needle-like super-structures, obtained via solvent vapour annealing (SVA) which are observed by Atomic Force Microscopy (AFM) and Optical Microscope. In particular, SVA is a powerful technique to fabricate reproducible self-assembled structures featuring high crystalline order, obtained tuning the experimental conditions such as solvent and temperature [4-5]. In particular, the obtained super-structures show high thermal stability, up to 150 °C, while the superatom complex remains stable up to 300°C. Here we present in-situ and ex-situ monitoring of thermal decomposition of the prepared super-structures in nitrogen atmosphere in the range between 25-300°C. Small-angle/Wide-angle X-ray scattering (SAXS/WAXS[6]) measurements clearly show the features of a Van der Waals crystalline structure with different packings of the in-plane and out-of-plane super-structures. The layered structure of the material is confirmed by AFM analysis. Moreover, SAXS images reveal the presence of aggregates with HCP structure which undergo a structural transition before degrading. The kinetics and the mechanisms of degradation are studied in-situ by Mass Spectroscopy (MS) and X-ray Photoemission Spectroscopy (XPS) in ultra-high vacuum (p = 10-9 mbar). These measurements reveal the presence of solvent trapped into the matrix that stabilised the super-structures up to 150 °C. For higher temperatures, the system collapses with the leakage of solvent. 1O.M.,Bakr, et al. Angewandte Chemie, 2009, 48(32), 5921-5926. 2 A.,Desireddy, et al. Nature,2013, 501(7467), 399-402. 3 H. Y.,Yang, et al. Nature Com., 2013, 4, 8. 4 G., De?Luca, et al., Adv. Func. Mat., 2007, 17(18), 3791-3798. 5 E., Treossi, et al. (2009). Small, 2009, 5(1), 112-119. 6 Elettra Synchrotron of Trieste, Basovizza TS.

Resume : Despite the tremendous efforts to experimentally achieve size and shape control of multinary nanocrystals, the underlying mechanistic processes leading to nanocrystal nucleation and subsequent growth are poorly understood. Early stage nucleation and subsequent growth of Cu2ZnSnS4 nanocrystals, which have demonstrated significant promise as photon absorbing layers for solar cells, are investigated by real-time in-situ measurements of the X-ray absorption fine structure (QEXAFS) at the Cu and Zn K-edges simultaneously. Also small angle X-ray scattering (SAXS) and optical transmission was recorded in-situ. The QEXAFS experimental setup allowed to investigate the chemical reaction within timescales of several 10 ms which enables the investigation of early reaction stages. We found the monodispersed nanocrystals to grow within six well-distinguishable reaction stages, the kinetics of which are influenced by the choice of ligands and solvents. Depending on the specific temperature profile applied, early stage nucleation was found to be completed after about 100 ms and is followed by subsequent incorporation of further cationic species. Combining the simultaneously measured data of complementary techniques we will present a detailed view of the processes occurring during synthesis of multinary nanocrystals.

Resume : The focus of my talk will address the difficulty to measure the structure of catalytically active sites in heterogeneous catalysis. Most catalysts have large structural heterogeneity and the identification of what constitutes the active site is very complex. In supported metal catalysts, the support cannot be assumed to be an inactive component. Ceria is a well-known support that is able to store and release oxygen. For that reason, it finds application in oxidation reactions. Upon oxygen release, part of CeIV is reduced to CeIII. The ceria oxygen-storage capacity and the presence of CeIII are often related to catalytic performance. By building on recently developed spectroscopic tools based on x-ray absorption and emission spectroscopy, we have been able to quantify the role of CeIII in the oxidation of carbon monoxide over Pt/CeO2. Transient measurements with high time resolved x-ray emission spectroscopy showed the existence of CeIII as spectator and as active intermediate in the reaction. The consequences of these observations on the relationship between oxygen storage capacity and the presence of CeIII on catalytic performance will be discussed.

Resume : NOx in emission gases can be reduced using a selective catalytic reduction (SCR) catalyst, which often consists of a vanadia (VOx) phase supported on anatase-TiO2. However, fundamental questions in relation to the atomic structure of the catalytically active surface, the nature of the active sites, and reaction pathways of the SCR process remain unanswered. Here we present synchrotron X-ray Photoelectron Spectroscopy (XPS, ASTRID, Aarhus and MaxLab, Lund) and atom-resolved Scanning tunneling microscopy (STM) results for the characterization of a V/a-TiO2 (101) SCR model catalyst. Upon deposition of sub-monolayer V at 100 K, the V is identified to be in a 2+ oxidation state indicating a preferred binding to surface oxygen atoms, and vanadium nucleates as small homogeneous clusters across the surface terraces. By heating up to room temperature vanadium shifts oxidation state to 3+/4+ and STM combined with DFT points towards a (near-)surface migration of V, where monomeric V species occupies Ti surface sites. The V-support interaction are further investigated as a function of temperature, V coverage and environment (O2, H2O, NH3). We are additionally using ambient pressure XPS (MaxLab, Lund), which allows us to mimic catalytically working conditions. Near-ambient pressures of oxygen also allows for fully oxidizing vanadium to 5+, the putative active oxidation state in SCR catalysis, hence partly bridging the materials gap between model and industrial catalyst. The combined STM and XPS studies demonstrate a strong correlation between V oxidation state and coordination on the anatase substrate, and understanding such V-support interaction may be key to modelling the active site of the SCR catalyst

Resume : Au-Pd bimetallic nanoparticles (NPs) have been extensively studied for their high catalytic activity in CO oxidation reaction. The preparation technique of the nanoparticles and the type of support has great impact on the catalytic behavior of the system. Here, 15 nm AuxPd1-x (x = 0, 0.25, 0.5, 0.75, 1) nanoparticles were prepared on SiOx/Si(100) via micelle nanolithography, a technique well adapted to yield minimal size distribution of nanoparticles. We follow a systematic approach to study the effect of oxygen and hydrogen plasma on the formation of the nanoparticles at different concentrations by means of surface x-ray scattering experiments performed at SixS Beamline, Synchrotron SOLEIL, France. The structure of AuxPd1-x NPs was investigated by means of grazing incidence x-ray diffraction measurements (GIXRD). The observed lattice constants were found to depend on the composition of nanoparticles as expected by the Vegard?s law. The oxidation/reduction behaviors, as well as the activity under operando conditions were studied by GIXRD using the flow reactor available at SixS beamline. In addition, the surface composition and chemical configuration of the of the as-synthesized AuxPd1-x NPs dispersed on silicon wafers was studied by x-ray photoelectron spectroscopy (XPS) at the ALOISA beamline, ELETTRA Synchrotron, Italy.

Resume : Nanoparticles formed within an ablation plume produced by the impact of a nanosecond laser pulse on the surface of an aluminum target have been directly measured using small-angle x-ray scattering (SAXS) [1]. The target was immersed in an oxygen-nitrogen gas mixture at atmospheric pressure with different O2/N2 ratio being precisely controlled. The results for an increasing oxygen content reveal remarkable effects on the morphology of the generated particles, which include a decrease in the particle volume but a marked increase in its surface ruggedness. Molecular dynamics simulations using a reactive potential and performed under similar conditions as the experiment reproduce the experimental trends and show in detail how the shape and surface structure of the nanoparticles evolve with increasing oxygen content [2]. Ex ? situ analysis using local observation such MET and Raman spectroscopy but also nuclear reaction (NRA) for elementary quantification of nitrogen and oxygen in the NPs has been performed to correlate the oxynitruration chemical with previous observation and simulation. This good agreement between in situ observations in the plume and atomistic simulations emphasizes the key role of chemical reactivity together with thermodynamic conditions on the morphology of the particles thus produced. [1] L. Lavisse, J-L. Legarrec, L. Hallo, Appl. Phys. Lett. 100, 164103 (2012) [2] G-D. Förster, M. Girault, J. Menneveux, Phys. Rev. Let.115, 246101 (2015)

Resume : Recently, ultrathin gold nanowires which exhibit a mean diameter in the range 1.5-2 nm and a micrometer length, attracted lots of interest due to their remarkable conductivity properties. Two strategies have been followed to synthesize these ultrathin nanowires : a gold salt is reduced in pure oleylamine (OY), which involves the precipitation of an intermediate solid phase, or in a solution containing OY and an additional reducing agent. These approaches lead to ultrathin Au NWs along with other spheres. The quantitative analysis of the different populations, and therefore the Au NWs yield cannot be easily addressed, moreover the question of the growth mechanism remains. Real-time SAXS enables to address both questions. The superiority of the reduction of chloride gold precursor in isotropic environment is evidenced, a reaction yield of 75% being observed, an order of magnitude higher than the route involving the lamellar phase. The soft template role of the [OY-AuICl] intermediate solid phase was thus discarded for the nanowire growth. The formation of hexagonal superlattices of ultrathin gold nanowires is for the first time evidence in the liquid phase. The unprecedented interwire distance of 8 nm suggests a bilayer stabilisation of Au NWs while DFT calculations evidence a cooperative adsorption and organisation of ions pairs at their surface. We propose that this charged backbone play a key role in the unique growth mechanism of such anisotropic objects.

Resume : Understanding the driving forces controlling phase formation is essential for the efficient synthesis and design of new materials, particularly metal-organic frameworks (MOFs), where mild solvothermal synthesis often allows access to various phases from the same reagents. Using high energy, in-situ synchrotron X-ray powder diffraction we have monitored the crystallization of a model family of MOFs and observed successive crystallizations and dissolutions of three competing phases in one reaction.[1] By determining rate constants and activation energies, we have mapped out the reaction energy landscape, which gives us quantitative predictive power for choice of reaction conditions for the first time. Different reaction rates are explained by the structural relationships between products and the reactants; larger changes in conformation result in higher activation energies. The experimental and analytical methods we have used can easily be applied to other materials, potentially opening the door to greater understanding of crystallization in general. Reference: [1] H. H.-M. Yeung et al., Angewandte Chemie International Edition, 2016, in press. DOI: 10.1002/anie.201508763.

Resume : To better understand the structural aspects of lithiation of crystalline Si, we have studied the lithiation process of single crystal Si using X-ray Reflectivity (XRR). We have designed an X-ray transparent cell for real time, in-situ XRR in a half cell configuration, with lithium metal as counter/reference electrode. This allows us to study the LixSi layer and any surface layers that form (e.g., solid electrolyte interface (SEI)) during lithiation. In-situ XRR data was obtained at three current densities: 25, 50 and 100 ?A/cm2. By fitting the data, we develop a detailed, mechanistic model of the initial lithiation process in crystalline Si. The lithiaiton starts by Li+ intercalation into native oxide at 0.7-0.2 V, forming lithium silicate and lithiated Si (LixSi) with ~5 nm thickness. Then bulk Si starts lithiation at ~0.1 V and we find a LixSi layer (with x?4) begins to form with a thickness that increases linearly with the charge passed. The density of this layer decreases in the early discharge stage, then remains constant. Recent studies have shown that a well-defined phase boundary exists between LixSi and crystalline Si during the lithiation of single crystal Si [1], and we find the Si/LixSi interface is smooth with a roughness is from 7 to 10 Å depending on current density. We also find a denser interface layer between the electrolyte and LixSi and speculate that this is part of the SEI layer. [1] Chon, Michael J., et al. Physical Review Letters107.4 (2011): 045503.

Resume : Formation of laser induced periodic surface structures (LIPSS) has been observed on polymers upon irradiation with a linearly polarized laser beam, at wavelengths efficiently absorbed and within a narrow fluence range below the ablation threshold. LIPSS are the result of the interference between the incoming and the surface-scattered waves together with a feedback mechanism. The use of grazing incidence X-ray scattering techniques with synchrotron radiation can be very useful for LIPSS analysis as they can provide kinetic information in the millisecond range and structural information statistically averaged over a large area. We report on the formation of LIPSS on conjugated polymers of interest in organic photovoltaics upon irradiation with the second and fourth harmonics of a Nd:YAG laser (532 and 266 nm) followed online by synchrotron Grazing Incidence X-ray Scattering at small (GISAXS) and wide (GIWAXS) angles. In situ measurements were performed at the DUBBLE beamline of the European Synchrotron Radiation Facility in order to study the evolution of the structural features online upon repetitive irradiation and to obtain information about the mechanisms involved in LIPSS formation. The number of pulses needed for the onset of LIPSS formation and for achieving the optimal order of the structures varies for the different polymers and irradiation conditions. The real time monitoring allows online optimization of both laser fluence and repetition rate for LIPSS formation.

Resume : Organic photovoltaics based on polymer-fullerene systems provide decent efficiency in power conversion and medium term stability. To allow large-scale production of these devices, control of the nanostructure during the processing of the active layer is important. We use the advanced scattering techniques grazing incidence wide and small angle x-ray scattering (GISAXS/GIWAXS) at the Advanced Light Source, USA, to investigate in-situ, printed active layers using an industrial slot-die coater. [1] We can follow the evolution of thin film morphology with appropriate time-resolution to initially track the solvent removal, followed by the crystallization of the polymer and the aggregation of the fullerene. The morphological evolution can be separated into several subsequent phases that take place independently of the drying speed of the film. The final film morphology, however, depends on the processing speed, because the individual processes compete with each other differently depending on time. [1] S. Pröller, F. Liu, C. Zhu, C. Wang, T.P. Russell, A. Hexemer, P. Müller?Buschbaum, E.M. Herzig, Advanced Energy Materials, 6: 1501580 (2016)

Resume : With perfectly defined monomer sequence and chain length, recombinant peptides obtained by protein engineering allow investigating the structure-property relationships at a level of detail difficult to achieve with synthetic polymers. In this work [1], we studied the temperature-triggered self-assembly of a series of recombinant elastin-like diblock peptides (ELP). Diblock ELP solutions were studied below and above the critical micellar temperature (CMT) by multi-angle dynamic light scattering and small-angle neutron scattering. Below the CMT, the radius of gyration follows a power law as a function of molecular weight with an exponent close to 0.5, characteristic of Gaussian coils. When the temperature reaches the CMT, attractive interactions between the more hydrophobic block of the diblock ELP chains lead to their self-assembly into monodisperse spherical nanoparticles at thermodynamic equilibrium. Above the CMT, micelles expel water molecules from their core down to a hydration level of only 2 D2O molecules per aminoacid, increasing the light and neutron scattering contrasts. The behavior of these diblock ELPs in solution and as self-assembled nanoparticles follows universal experimental scaling laws: Similarly to synthetic amphiphilic diblock copolymers forming “star-like” or “crew-cut” micelles, diblock ELPs form structures named “weak micelles” by Rubinstein et al [2]. [1] Garanger et al, Macromolecules 2015, 48, 6617. [2] Hassouneh at al, Macromolecules 2015, 48, 4183.

Resume : Activated carbons are industrially relevant materials whose properties depend on morphology, texture and surface features. The deep characterization of this class of materials is a fundamental step for understanding their potential in a variety of applications. Unfortunately, many characterization techniques, and in particular light spectroscopies, are difficult to be applied on carbons, due to the intrinsic strong intrinsic strong interaction of carbons with electromagnetic radiation in the region from UV to IR. Inelastic Neutron Scattering (INS) eliminates the problem of radiation interaction and is sensitive to vibrations involving light elements, mostly hydrogen including species, which are abundant on carbons surface. However, this technique alone is not sufficient to have the complete set of information about the material; it is then necessary to couple INS with other techniques, such as DRIFT spectroscopy (sensitive to vibrations involving a dipole change) and back-scattering Raman spectroscopy (sensitive mostly to apolar vibrational modes, typical of carbon bulk). The whole set of experimental data is interpreted with the help of DFT calculations, helping us to point out their structural and surface properties.

Resume : We have studied hydrogen storage in a new class of metal-organic frameworks CAU-1, synthesized at the University of Kiel, Germany. CAU-1 consists of corner- and edge shared 8-member-rings of Aluminum octahedral, which are connected with aminoterephthalate as linker molecules. The CAU-1 forms two different nanocages: (i) an octahedral cage structure with a diameter of about 1 nm and (ii) a tetrahedral cage structure with a diameter of about 0.5 nm. Though all Al sites are saturated CAU-1 exhibits surprisingly high storage capacities reaching to 5 wt% at temperature of 70K and 1 wt% at 120K. We have applied multidisciplinary approach of volumetric gas sorption analysis, in-situ neutron diffraction and spectroscopy with ab-initio structure modelling to investigate the mechanism of hydrogen sorption in this system. Our study reveal three stages of temperature dependence of hydrogen intake originating from partially parallel filling of two cavities and depending strongly on confinement dimensions. Furthermore, we observe that hydrogen sorption is driven by interactions between guest hydrogen molecules and hydrogen of organic linkers. The adsorption of hydrogen on the linkers leads to the shrinking of the host framework structure and as a result to changes in the electronic potential surface inside the pores. This in turn provide for the formation additional occupational positions and increase of hydrogen intake.

Resume : Stimuli-responsive self-assembly is an active field of research in soft matter due to the broad number of potential applications. [1] Block copolymers and lipids are commonly designed to tune their self-assembly properties in solution as a function of temperature (e.g., use of N-isopropylacrylamide residus), pH (use of amine or carboxylic acid residus) and ionic force (use of charged residus), etc... [2] Typical self-assembled structures range from simple spherical to branched micelles, disks, vesicles, sheets, fibers, just to cite some, and where the morphological relationship between them is generally considered to rely on the molecular structure, according to the well-known packing parameter relationship. [3] Cone-like molecular morphologies tend to form curved objects, like micelles, while cylinder-shaped molecules rather form flat sheets. However, this simplistic view, even if it can explain, or even predict on a thermodynamics basis, the shape of the micellar aggregates for various amphiphilic systems (e.g., ethylene oxide, ionic, gemini surfactants, ...), [4-6] it fails to describe many experimental facts, as this is well-known among physico-chemists. [7] In this presentation we will show how pH-resolved in-situ SAXS using synchrotron radiation will be of extreme importance to understand the mechanism of formation of four structurally-related COOH-containing glycolipids, new biobased compounds produced by microbial fermentation of biomass and at which the surfactant industry is looking with great interest due to their good biodegradability and low aquatic toxicity. All of them majoritary form micelles at basic pH but each one assembles into different structures below pH 7: micelles [8] and twisted ribbons [9] are respectively observed for monounsaturated and saturated sophorolipids (glucose beta1,2 disaccharide as hydrophilic headgroup) while vesicles and infinite sheets are respectively observed for monounsaturated and saturated glucolipids (glucose alone as hydrophilic headgroup). These experiments suggest that additional arguments, besides the packing parameter, must be used to explain both the relative morphological variations and the pH-driven mechanism of formation: melting temperature of the lipophilic region, COOH/COO- ratio, hydration of the sugar headgroup, bilayer membrane flexibility just to cite some. [1] E. Felber, M.-H. Dufresne, J.-C. Leroux, pH-sensitive vesicles, polymeric micelles, and nanospheres prepared with polycarboxylates, Adv. Drug Delivery Rev., 2012, 64, 979?992 [2] P. Brown, C. P. Butts, J. Eastoe, Stimuli-responsive surfactants, Soft Matter, 2013, 9, 2365-2374 [3] J. N. Israelachvili, D. J. Mitchell, B. W. Ninham, Chem. Soc., Faraday Trans. 2 1976, 72, 1525-1568 [4] R. Nagarajan, E. Ruckenstein Theory of Surfactant Self -Assembly: A Predictive Molecular Thermodynamic Approach, Langmuir 1991, 7, 2934-2969 [5] S. S. Berr, E. Caponetti, J. S. Johnson Jr., R. R. M. Jones, L. J. Magid, Small-angle neutron scattering from hexadecyltrimethylammonium bromide micelles in aqueous solutions, J. Phys. Chem., 1986, 90, 5766?5770 [6] P. Alexandridis, V. Athanassiou, S. Fukuda, T. A. Hatton, Surface Activity of Poly(ethy1eneoxide)-block-Poly(propy1ene oxide)-block-Poly(ethy1eneoxide) Copolymers, Langmuir 1994, 10, 2604-2612 [7] R. Nagarajan, Molecular Packing Parameter and Surfactant Self-Assembly: The Neglected Role of the Surfactant Tail, Langmuir 2002, 18, 31-38 [8] S. Manet, A.-S. Cuvier, C. Valotteau, G. C. Fadda, J. Perez, E. Karakas, S. Abel, N. Baccile, Structure of Bolaamphiphile Sophorolipid Micelles Characterized with SAXS, SANS, and MD Simulations, J. Phys. Chem. B, 2015, DOI: 10.1021/acs.jpcb.5b05374 [9] A.-S. Cuvier, J. Berton, C. V. Stevens, G. C. Fadda, F. Babonneau, I. N. A. Van Bogaert, W. Soetaert, G. Péhau-Arnaudet, N. Baccile, pH-triggered formation of nanoribbons from yeast derived glycolipid biosurfactants, Soft Matter, 2014,10, 3950-3959

Resume : A nondestructive neutron scattering method to precisely measure the uptake of hydrogen and the distribution of hydride precipitates in light water reactor (LWR) fuel cladding was developed. Zircaloy-4 clad- ding used in commercial LWRs was used to produce hydrided specimens. The hydriding apparatus consists of a closed stainless-steel vessel that contains Zr alloy specimens and hydrogen gas. Following hydrogen charging, the hydrogen content of the hydrided specimens was measured using the vacuum hot extraction method, by which the samples with desired hydrogen concentrations were selected for the neutron study. Optical microscopy shows that our hydriding procedure results in uniform distribution of circumferential hydrides across the wall thickness. Small angle neutron incoherent scattering was performed in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Our study demonstrates that the hydrogen in commercial Zircaloy-4 cladding can be measured very accurately in minutes by this nondestructive method over a wide range of hydrogen concentrations from a very small amount (~20 ppm) to over 1000 ppm. The hydrogen distribution in a tube sample was obtained by scaling the neutron scattering rate with a factor determined by a calibration process using standard, destructive direct chemical analysis methods on the specimens. This scale factor can be used in future tests with unknown hydrogen concentrations, thus providing a nondestructive method for determining absolute hydrogen concentrations. This research was sponsored by the Laboratory Directed Research and Development (LOIS-6502) Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725), and EBSD through a user project supported by ORNL?s Center for Nanophase Materials Sciences (CNMS), which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Beamline CG3 is supported by the Office of Biological and Environmental Research of the U.S. Department of Energy through the ORNL Center for Structural Molecular Biology. The High Flux Isotope Reactor and beamline CG2 of ORNL was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. We are grateful to Dr. Jeremy Busby for his technical inputs and stimulating discussions.

Resume : Scanning X-ray nanodiffraction is an excellent tool for materials science related in situ studies. It readily serves structural information with sub-µm spatial resolution from crystalline and semi-crystalline materials (metals, biomaterials, synthetic compounds). That way grain orientation, residual stress profiles, crystal structure or texture can be obtained in a non-destructive analysis. Because of the long focal distance focusing, the wide X-ray energy range and a flexible sample positioning system, high resolution nanodiffraction experiments can be performed even under demanding conditions e.g. on strongly absorbing metallic samples or in extended sample environments. The Nanofocus Endstation of beamline P03 (PETRA III, Hamburg) is part of the German Engineering Materials Science Center (GEMS) and is operated jointly by Helmholtz-Zentrum Geesthacht and the University of Kiel. It is one of only few places in the world where the experimental conditions for scanning X-ray nanodiffraction are provided and it offers a hard X-ray beam with a size of only 250 x 350 nm². The strong focus on materials science at P03 is demonstrated by the wide range of experiments already performed with in situ sample environments: pressure, indentation force, tensile stress, fluid shear, magnetic fields - all of these parameters were successfully modified in situ and combined with the high spatial resolution provided by nanofocused beam.

Resume : Many modern technological processes for prospective applications within catalysis, photovoltaics, photonics, etc., suffer from the lack of nanoscale-ordered materials. The formation of such structures may naturally be based on phenomena of hierarchical self-organization processes in materials. For example, nanoporous anodic aluminum oxide films (NP-AAO) formed under certain conditions exhibit a remarkably-well-ordered porous structure [1] that could be used for engineering of hierarchically ordered objects. However, despite significant progress in exploring NP-AAOs and their properties, the majority of recent and current studies are limited to ex situ experiments, mostly concerning electron microscopy on the already-prepared samples [1-3]. At the same time, there is a significant lack of in situ structural studies of NP-AAOs that could reveal peculiarities or other regularities of structural ordering during NP-AAOs formation, not observed by ex situ experiments. Here we report on the formation and evolution of a remarkable X-ray scattering pattern in grazing incidence geometry (GISAXS), obtained from an aluminum sample upon its anodization in an electrochemical cell, in operando. The analysis of this pattern allows calculating a multitude of structural parameters of the NP-AAO: pore shape and size, interpore distance, size of coherent domains, etc. The observation of the periodic X-ray pattern in the direction normal to the surface allows for the precise determination of the pore formation rate. Our approach is not limited to aluminum only, but can be applied to a number of other elements, and paves the way for in situ studies of the effect of changing the electrolyte and electrodeposit other materials into the pores. References: [1] H. Masuda, M. Satoh. Jpn. J. Appl. Phys. A 35, L126 (1996) [2] G. Poinern, N. Ali and D. Fawcett. Materials 4, 487 (2011) [3] A. Jani, D. Losic, N. Voelcker. Prog. In Mat. Sci. 58, 636 (2013)

Resume : Time-resolved in-situ studies of thin film formation processes through the use of high-energy (>50 keV) synchrotron radiation can provide valuable information about the effect of deposition parameters on reaction pathways and reaction kinetics. While lab-scale environments for in-situ studies if film formation exists, time resolved XRD studies of film growth under industry-relevant conditions have not yet been realized. We present a, large-scale, UHV-based magnetron sputter and cathodic arc deposition system purposefully designed for time-resolved in-situ thin film deposition/annealing studies using high-energy (> 50 keV), high photon flux (>10^12 ph/s) synchrotron radiation, under such conditions. The high photon flux, combined with a fast-acquisition-time (< 1 s) two dimensional (2D) detector, permits time-resolved in situ structural analysis of thin film formation processes. The high-energy synchrotron-radiation based x-rays result in small scattering angles (< 11degrees), allowing large areas of reciprocal space to be imaged with a 2D detector. The UHV chamber allows for a range of applications, from wide band-gap semiconductor epitaxy to high rate depositions of hard wear-resistant coatings. It is demonstrated here by time-resolved phase stability and film stress evolution, during reactive magnetron sputter deposition of 300 nm-thick layers of the novel hard tool coatings Zr(x)Al(1-x)N, at the P07 High Energy Materials Science beamline at PETRA III in Hamburg, Germany.

Resume : Non-Crystalline Diffraction permits the study of structural properties of non- or semi-crystalline states of matter. Small Angle X-Ray Scattering (SAXS) and Wide Angle X-ray Scattering (WAXS) are widely used for observing phase changes or conformational rearrangements on a length scale ranging from 10 to 5000 Å. BL11, in ALBA synchrotron light source, is a versatile beamline where a wide range of polymer nanomaterials are being studied1. The in vacuum undulator delivers high photon flux (1012 ph/s/0.1%b.w.) into a focused 100x50 µm2 spot in the energy range 5-13keV. Static or time resolved simultaneous SAXS/WAXS measurements can be performed. The SAXS photon counting detector allows fast data collection (100 frames/sec). Linkam devices are available allowing the study of solid and liquid systems during crystallisation and melting. A Linkam stretching device will be offered soon. A flexible sample platform can accommodate custom user-sample-environments. The newly established BL11 has proven its huge capabilities and potential in material sciences and the study of nanomaterials, with applications amongst others, in the construction of new polymers and bio-engineering2-6. 1. NCD beamline, ALBA Synchrotron Light Source http://www.cells.es/en/beamlines/bl11-ncd 2. Reguero V. et al., 2014, Chem of Materials, 26, 3550 3. Terrones J. et al., 2014, ACS NANO, 8 , 8497 4. Márquez Y. et al., 2015, FIBERS, 3, 348 5. Díaz A. et al., 2015, POLYMERS, 7, 1871 6. Khan I. et al., 2016, IOP in press

Resume : Resistively switching transition metal oxides are gaining in importance as promising materials for next-generation non-volatile memory applications. It is widely accepted that resistive switching is connected with a voltage-driven oxygen-ion migration and resulting redox processes. These redox processes are believed to be responsible for a localized change of the resistance, but direct observation and quantification of the switching mechanism itself remain challenging. One of the main obstacles is that the net changes of structure, stoichiometry, and valence state upon switching are very small and occur primarily at electrode interfaces or within nanoscale filaments. Here we will present local changes in the electronic structure of SrTiO3-based memristive devices utilizing operando photoemission electron microscopy (PEEM) in X-ray absorption mode. To overcome the surface sensitivity of PEEM, photoelectron-transparent graphene top electrodes are used to attain spectroscopic information from the buried SrTiO3 layer of functioning devices. This novel approach enables in-situ switching and allows for the characterization of both resistance states of a single device. Reversible changes of the O K-edge absorption spectra within spatially confined regions provide a quantitative estimate of the redox reaction, which is consistent with the observed change in resistance. This finding confirms that resistive switching in SrTiO3 is caused by localized redox reactions. Apart from operando characterization of resistive switching processes, employment of such photoelectron-transparent electrodes paves the way for characterization of numerous field- or current-driven processes on the nanoscale under operation condition.