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Scan free grazing emission X ray fluorescence spectroscopy GEXRF is an established technique for the investigation of the elemental depth profiles of various samples. Recently it has been applied to investigating structured nanosamples in the tender X ray range. However, lighter elements such as oxygen, nitrogen or carbon cannot be efficiently investigated in this energy range, because of the ineffective excitation. Moreover, common CCD detectors are not able to discriminate between fluorescence lines below 1 keV. Oxygen and nitrogen are important components of insulation and passivation layers, for example, in silicon oxide or silicon nitride. In this work, scan free GEXRF is applied in proof of concept measurements for the investigation of lateral ordered 2D nanostructures in the soft X ray range. The sample investigated is a Si3N4 lamellar grating, which represents 2D periodic nanostructures as used in the semiconductor industry. The emerging two dimensional fluorescence patterns are recorded with a CMOS detector. To this end, energy dispersive spectra are obtained via single photon event evaluation. In this way, spatial and therefore angular information is obtained, while discrimination between different photon energies is enabled. The results are compared to calculations of the sample model performed by a Maxwell solver based on the finite elements method. A first measurement is carried out at the UE56 2 PGM 2 beamline at the BESSY II synchrotron radiation facility to demonstrate the feasibility of the method in the soft X ray range. Furthermore, a laser produced plasma source LPP is utilized to investigate the feasibility of this technique in the laboratory. The results from the BESSY II measurements are in good agreement with the simulations and prove the applicability of scan free GEXRF in the soft X ray range for quality control and process engineering of 2D nanostructures. The LPP results illustrate the chances and challenges concerning a transfer of the methodology to the laboratory

FeNi Hydroxides (FeNi-HD) have been considered as promising substitutes to noble metal electrocatalysts for oxygen evolution reaction (OER). In this work, we design and realize FeNi-HD nanotube arrays (FeNi-HDNAs) on Ni foam via an in-situ reaction and Kirkendall effect. The obtained catalysts possess higher specific surface area, more catalytic active sites and better chemical stability for OER. Electron migrations from the Fe 3d orbitals to Ni sites in the FeNi-HDNAs lead to more unoccupied Fe 3d states and a higher oxidation state. As expected, FeNi-HDNAs exhibit lower overpotential as well as lower Tafel slope and better durability than the Fe- or Ni-HD peers. DFT calculations elucidate that FeNi hydroxides lower the energy barrier of rate-determining step in OER. Moreover, a high current density of 10 mA cm−2 is obtained at a low potential of 1.49 V using FeNi-HDNAs as the bifunctional electrocatalyst for overall water splitting in basic solution.

M. Guerra acknowledges the support of the FCT, under Contract No. SFRH/BPD/92455/2013. This work was supported in part by the research center Grants No. UID/FIS/04559/2013 to LIBPhys-UNL, and No. UID/MULTI/04046/2013 to BioISI, from the FCT/MCTES/PIDDAC. Laboratoire Kastler Brossel is "Unite Mixte de Recherche du CNRS, de l' ENS et de l'UPMC" No. 8552. Parts of this work have been carried out in the framework of the Project 14IND01 3DMetChemIT, funded by the EMPIR program, co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation program. Fluorescence yields (FY) for the Ni K and L shells were determined by a theoretical and an experimental group within the framework of the International Initiative on X-ray Fundamental Parameters (FPs) collaboration. Coster-Kronig (CK) parameters were also measured for the L shell of Ni. Theoretical calculations of the same parameters were performed using the Dirac-Fock method, including relativistic and QED corrections. The experimental values for the FY and CK were determined at the PTB laboratory in the synchrotron radiation facility BESSY II, Berlin, Germany, and are compared to the corresponding calculated values. publishersversion published

Proceedings of the 17th European Conference on X-Ray Spectrometry (EXRS), 19-24 June 2016, Gothenburg, Germany.; International audience; A new instrument called CASTOR is operated at the SOLEIL synchrotron facility and is dedicated to the characterization of thin films with thicknesses in the nanometer range. The instrument can combine X-ray reflectivity measurements with fluorescence (XRF) acquisitions and especially total reflection X-ray fluorescence-related techniques such as grazing incidence XRF. The instrument was successfully installed and operated on the two branches of the metrology beamline making possible experiments over a wide range of photon energies (45 eV to 40 keV). A heating sample holder was developed to allow the sample temperature to be controlled up to 300° C. Some examples of the first studies are given to illustrate the capabilities of the setup

Nondestructive methods based on electron emission may encounter serious difficulties when probing the chemical state of deeply buried nanolayers due to restricted information depth. The purpose of the present work is to evaluate to which extent photon emission can overcome these restrictions. Grazing-incidence x-ray fluorescence combined with a near-edge x-ray absorption fine-structure investigation (GIXRF-NEXAFS) offers access to depth-resolving analysis of buried nanolayers with respect to both the chemical speciation and the layer composition. By varying the angle of incidence, the penetration depth can be tuned from a few to several hundreds of nanometers. The information depth of the emitted fluorescence radiation is in the same general range as the soft x-ray regime. Initial measurements were performed on nominally 30 nm thick titanium nanolayers oxidized to different extents and buried below 5 nm carbon layers. These layered structures were produced by means of ion beam sputtering deposition. The plane grating monochromator beamline for undulator radiation in the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II provides tunable radiation of both well-known flux and high spectral purity for GIXRF-NEXAFS studies. The current results confirm that GIXRF-NEXAFS has the potential to substantially contribute to the speciation of deeply buried nanolayers. The analysis of measurements at a constant incident angle demonstrated that it is not possible to find an angle of incidence for the NEXAFS region to ensure a stable penetration depth. However, appropriate angular corrections can ensure a constant mean penetration depth, in particular, in the vicinity of absorption edges.