| 1. |
- Adak, S., et al.
(författare)
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Study of oxidation states of the transition metals in a series of Prussian blue analogs using x-ray absorption near edge structure (XANES) spectroscopy
- 2017
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 214, s. 8-19
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Tidskriftsartikel (refereegranskat)abstract
- There have been renewed interests in metal-organic framework classes of materials such as Prussian blue analogues (PBAs) due to their potential usage in energy storage applications. In particular, due to their high surface areas, controllable structures and excellent electrochemical properties, PBAs such as hexacyanometalates MII3[AIII(CN)6]2*nH2O (M = Mn, Fe, Co, Ni, Cu, Zn; A = Co, Fe, Cr; n = no. of water molecules present), MII2[FeII(CN)6]2*nH2O (M = Mn, Co, Ni, Cu, Zn) and mixed hexacyanometalates(III) (Fe1-xCox)3[BIII(CN)6]2·nH2O (x = 0.25, 0.5, 0.75; B = Co, Fe) could have possible usage as a new class of cathode and even anode materials for rechargeable batteries. Detailed knowledge of the oxidation states of the transition metals in PBAs is required to improve efficiency and durability of such devices. Furthermore, a link between the thermal expansion observed in these materials and the oxidation state of the transition metal is of interest to synthesize materials with a desired thermal expansion behavior, Here we demonstrate the use of Synchrotron based X-ray absorption near-edge structure (XANES) spectra to identify transition metal oxidation states. Our analysis reveals the presence of divalent, trivalent and/or mixed valence transition metals in the materials as well as high-spin and low-spin complexes.
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| 2. |
- Andersson, Åke, et al.
(författare)
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Future development plans for the MAX IV light source: Pushing further towards higher brightness and coherence
- 2018
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 224
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Tidskriftsartikel (refereegranskat)abstract
- The commissioning of the MAX IV synchrotron radiation facility in Lund marks the dawn of a new generation of storage-ring-based light sources. This new generation delivers one order of magnitude higher performance and allows realization of groundbreaking experiments on a variety of systems and materials at the atomic and molecular levels. This paper reviews the conceptual basis of the MAX IV design, briefly summarizes the most recent accelerator commissioning results and focusses on exploring a future development path for the MAX IV 3 GeV storage ring aimed at achieving the diffraction limit at hard x-ray wavelengths.
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| 3. |
- Bidermane, Ieva, 1984-, et al.
(författare)
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Atomic Contributions to the Valence Band Photoelectron Spectra of Metal-free, Iron and Manganese Phthalocyanines
- 2015
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 205, s. 92-97
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Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- The present work reports a photoelectron spectroscopy study of the low-energy region of the valence band of metal-free phthalocyanine (H2Pc) compared with those of iron phthalocyanine (FePc) and manganese phthalocyanine (MnPc). We have analysed in detail the atomic orbital composition of the valence band both experimentally, by making use of the variation in photoionization cross-sections with photon energy, and theoretically, by means of density functional theory. The atomic character of the Highest Occupied Molecular Orbital (HOMO), reflected on the outermost valence band binding energy region, is different for MnPc as compared to the other two molecules. The peaks related to the C 2p contributions, result in the HOMO for H2Pc and FePc and in the HOMO-1 for MnPc as described by the theoretical predictions, in very good agreement with the experimental results. The DFT simulations, discerning the atomic contribution to the density of states, indicate how the central metal atom interacts with the C and N atoms of the molecule, giving rise to different partial and total density of states for these three Pc molecules.
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| 4. |
- Duda, Laurent, et al.
(författare)
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Oxygen redox reactions in Li ion battery electrodes studied by resonant inelastic X-ray scattering
- 2017
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier. - 0368-2048 .- 1873-2526. ; 221, s. 79-87
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Tidskriftsartikel (refereegranskat)abstract
- We present results using inelastic scattering x-ray spectroscopy (RIXS) combined with x-ray absorption spectroscopy on Li ion battery cathode and anode materials, respectively. In particular, we discuss results obtained on the cathode materials Li1.2[Ni0.13Co0.133Mn0.544]O2 and Lix[Ni0.65Co0.25Mn0.1]O2 as well as in the composite anode material Ni0.5TiOPO4/C. We show that oxygen redox reactions are an important aspect of many such systems and how one can succesfully address them using RIXS. New insights on the formation of new oxygen species and on the details of cycling-induced structural disorder can be detected. We foresee a particular future focus on these issues considering the rapid development of new in operando RIXS techniques for Li ion battery research.
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| 5. |
- Eiteneer, D., et al.
(författare)
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Depth-Resolved Composition and Electronic Structure of Buried Layers and Interfaces in a LaNiO3/SrTiO3 Superlatticefroni Soft- and Hard-X-ray Standing-Wave Angle-Resolved Photoemission
- 2016
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 211, s. 70-81
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Tidskriftsartikel (refereegranskat)abstract
- LaNiO3 (LNO) is an intriguing member of the rare-earth nickelates in exhibiting a metal-insulator transition for a critical film thickness of about 4 unit cells [Son et al., Appl. Phys. Lett. 96, 062114 (2010)]; however, such thin films also show a transition to a metallic state in superlattices with SrTiO3 (STO) [Son et al., Appl. Phys. Lett. 97, 202109 (2010)]. In order to better understand this transition, we have studied a strained LNO/STO superlattice with 10 repeats of [4 unit-cell LNO/3 unit-cell STO] grown on an (LaAlO3)(0.3)(Sr2AlTaO6)(0.7) substrate using soft x-ray standing-wave-excited angle-resolved photoemission (SWARPES), together with soft- and hard- x-ray photoemission-measurements of core levels and densities-of-states valence spectra. The experimental results are compared with state-of-the-art density functional theory (DFT) calculations of band structures and densities of states. Using core-level rocking curves and x-ray optical modeling to assess the position of the standing wave, SWARPES measurements are carried out for various incidence angles and used to determine interface-specific changes in momentum-resolved electronic structure. We further show that the momentum-resolved behavior of the Ni 3d e(g) and t(2g) states near the Fermi level, as well as those at the bottom of the valence bands, is very similar to recently published SWARPES results for a related La0.7Sr0.3MnO3/SrTiO3 superlattice that was-studied using the same technique (Gray et al., Europhysics Letters 104, 17004 (2013)), which further validates this experimental approach and our conclusions. Our conclusions are also supported in several ways by comparison to DFT calculations for the parent materials and the superlattice, including layer-resolved density-of-states results.
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| 6. |
- Fondell, Mattis, 1984-, et al.
(författare)
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Surface modification of iron oxides by ion bombardment – comparing depth profiling by HAXPES and Ar ion sputtering
- 2018
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier. - 0368-2048 .- 1873-2526. ; 224, s. 23-26
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Tidskriftsartikel (refereegranskat)abstract
- Iron oxide in the form of maghemite γ-Fe2O3 and hematite α-Fe2O3 has been studied with x-ray photoelectron spectroscopy. It is found that even low energy sputtering induces a reduction of the surface layer into FeO. Satellites in the Fe 2p core level spectra are used to determine the oxidation state of iron. Depth profiling with changing photon energy shows that the unsputtered films are homogeneous and that the information obtained from sputtering thus, in this instance, represents sputter damages to the sample.
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| 7. |
- Giangrisostomi, Erika, et al.
(författare)
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Low Dose Photoelectron Spectroscopy at BESSY II : Electronic structure of matter in its native state
- 2018
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier. - 0368-2048 .- 1873-2526. ; 224:SI, s. 68-78
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Tidskriftsartikel (refereegranskat)abstract
- The implementation of a high-transmission, angular-resolved time-of-Right electron spectrometer with a 1.25 MHz pulse selector at the PM4 soft X-ray dipole beamline of the synchrotron BESSY II creates unique capabilities to inquire electronic structure via photoelectron spectroscopy with a minimum of radiation dose. Solid-state samples can be prepared and characterized with standard UHV techniques and rapidly transferred from various preparation chambers to a 4-axis temperature-controlled measurement stage. A synchronized MHz laser system enables excited-state characterization and dynamical studies starting from the picosecond timescale. This article introduces the principal characteristics of the PM4 beamline and LowDosePES end-station. Recent results from graphene, an organic hole transport material for solar cells and the transition metal dichalcogenide MoS2 are presented to demonstrate the instrument performances. (C) 2017 The Authors. Published by Elsevier B.V.
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| 8. |
- Gorgoi, Mihaela, et al.
(författare)
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HAXPES studies of solid materials for applications in energy and information technology using the HIKE facility at HZB-BESSY II
- 2015
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - Elsevier : Elsevier BV. - 0368-2048 .- 1873-2526. ; 200, s. 40-48
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Tidskriftsartikel (refereegranskat)abstract
- In the present work we review a number of research directions addressed at the HIKE end-station at the BESSY II storage ring at the Helmholtz-Zentrum Berlin, HZB, using hard X-ray photoelectron spectroscopy (HAXPES). The emphasis of this review is on the specific properties of the technique, which are required in order to address different scientific questions at the HIKE beamline.
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| 9. |
- Huotari, J., et al.
(författare)
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Separation of valence states in thin films with mixed V2O5 and V7O16 phases
- 2016
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 211, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Among the other applications, vanadium oxide thin films are considered to be excellent candidates for gas sensing. To understand the origins of the sensing capability, we carried out X-ray photoelectron and X-ray absorption spectroscopy measurements to determinate the surface valence states of thin films with mixed V7O16 and V2O5 compounds. Thin films were fabricated by pulsed laser deposition, and the crystal structure and symmetry of the deposited films was studied using grazing incidence X-ray diffraction and Raman spectroscopy. These results together with X-ray photoelectron and absorption spectra showed that the thin-film crystal structures varied between orthorhombic V2O5 phase and another phase of triclinic V7O16. X-ray photoelectron spectroscopy was used to quantitatively confirm the high amount of V4+ ions on surfaces of the films, especially of films with V7O16 phase present. This result was confirmed in the quantitative analysis of the V2p near-edge X-ray absorption spectra. Through the observed electronic structures, it was found that in addition to unique crystal structure and morphology, the enhanced gas sensitivity of these layers is attributed to the increase in the amount of surface oxygen vacancies.
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| 10. |
- Inoyatov, A. Kh., et al.
(författare)
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The experimental investigation of weak effects in the KLL Auger electron spectrum of Zr and Nb generated in radioactive decay
- 2018
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier. - 0368-2048 .- 1873-2526. ; 229, s. 61-67
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Tidskriftsartikel (refereegranskat)abstract
- The KLL Auger electron spectra of Zr (Z = 40) and Nb (Z = 41) following respectively the electron capture (EC) decay of Nb-90 and the de-excitation of the isomeric state of Nb-91m were investigated in detail using a combined electrostatic electron spectrometer and radioactive sources prepared by surface sorption on a polycrystalline carbon substrate. For both elements, energies, relative intensities, and natural widths of all the nine well-resolved basic spectrum components were determined and compared with theoretical predictions and with results of previous measurement as well. Results of our ab initio multieonfiguration Dirac-Hartree-Fock calculations are discussed also in relation to the solid-state effect. Indications of an influence of the EC decay on the absolute energy of the KL2L3(D-1(2)) transition (so-called atomic structure effect) in Zr were found. The effect of the retarded current-current interaction on the KL1L2(P-3(0)) transition intensity was observed to be appreciable for the investigated elements in accordance with the prediction.
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