Artykuły w czasopismach: „Spectroscopie HAXPES”

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Rao, P. N., U. K. Goutam, Prabhat Kumar, Mukul Gupta, Tapas Ganguli i S. K. Rai. "Depth-resolved compositional analysis of W/B4C multilayers using resonant soft X-ray reflectivity". Journal of Synchrotron Radiation 26, nr 3 (5.04.2019): 793–800. http://dx.doi.org/10.1107/s1600577519002339.

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W/B4C multilayers (MLs) consisting of ten layer pairs with varying boron carbide layer thicknesses have been investigated. The ML structures were characterized using grazing-incidence hard X-ray reflectivity (GIXR), resonant soft X-ray reflectivity (RSXR), hard X-ray photoelectron spectroscopy (HAXPES) and X-ray absorption near-edge spectroscopy (XANES). Depth-resolved spectroscopic information on the boron carbide layer in W/B4C MLs was extracted with sub-nanometre resolution using reflectivity performed in the vicinity of the B K-edge. Interestingly, these results show that the composition of boron carbide films is strongly dependent on layer thicknesses. HAXPES measurements suggest that most of the boron is in the chemical state of B4C in the multilayer structures. XANES measurements suggest an increase in boron content and C—B—C bonding with increase in boron carbide layer thickness.

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Egiza, Mohamed, Hiroshi Naragino, Aki Tominaga, Kenji Hanada, Kazutaka Kamitani, Takeharu Sugiyama, Eiji Ikenaga i in. "Effects of Air Exposure on Hard and Soft X-ray Photoemission Spectra of Ultrananocrystalline Diamond/Amorphous Carbon Composite Films". Coatings 8, nr 10 (9.10.2018): 359. http://dx.doi.org/10.3390/coatings8100359.

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Hard X-ray photoemission spectroscopy (HAXPES) was employed for the structural evaluation of ultrananocrystalline diamond/amorphous carbon (UNCD/a-C) composite films deposited on cemented carbide substrates, at substrate temperatures up to 550 °C by coaxial arc plasma deposition. The results were compared with those of soft X-ray photoemission spectroscopy (SXPES). Since nanocrystalline diamond grains are easily destroyed by argon ion bombardment, the structural evaluation of UNCD/a-C films, without the argon ion bombardment, is preferable for precise evaluation. For samples that were preserved in a vacuum box after film preparation, the sp3 fraction estimated from HAXPES is in good agreement with that of SXPES. The substrate temperature dependencies also exhibited good correspondence with that of hardness and Young’s modulus of the films. On the other hand, the sp3 fraction estimated from SXPES for samples that were not preserved in the vacuum box had an apparent deviation from those of HAXPES. Since it is possible for HAXPES to precisely estimate the sp3 fraction without the ion bombardment treatment, HAXPES is a feasible method for UNCD/a-C films, comprising nanocrystalline diamond grains.

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Ruwisch, Kevin, Tobias Pohlmann, Florian Bertram, Christoph Schlüter, Andrei Gloskovskii, Karsten Küpper i Joachim Wollschläger. "Real-Time Monitoring the Growth of Epitaxial CoxFe3−xO4 Ultrathin Films on Nb-Doped SrTiO3(001) via Reactive Molecular Beam Epitaxy by Means of Operando HAXPES". Materials 15, nr 7 (23.03.2022): 2377. http://dx.doi.org/10.3390/ma15072377.

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In this work, we present a comprehensive study on real-time monitoring the growth of epitaxial CoxFe3−xO4 thin films grown on SrTiO3(001) substrates via reactive molecular beam epitaxy. The growth process was monitored during evaporation by means of time resolved operando hard X-ray photoelectron spectroscopy (HAXPES). We prepared ultrathin ferrite films using different oxygen partial pressures, showing pure metallic, light oxidic, and cobalt ferrite-like growth. Additional X-ray diffraction measurements confirm HAXPES results.

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Chen, Min, Han Zhou, Benedikt P. Klein, Malte Zugermeier, Claudio K. Krug, Hans-Jörg Drescher, Mihaela Gorgoi, Martin Schmid i J. Michael Gottfried. "Formation of an interphase layer during deposition of cobalt onto tetraphenylporphyrin: a hard X-ray photoelectron spectroscopy (HAXPES) study". Physical Chemistry Chemical Physics 18, nr 44 (2016): 30643–51. http://dx.doi.org/10.1039/c6cp05894a.

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Rueff, J. P., J. M. Ablett, D. Céolin, D. Prieur, Th Moreno, V. Balédent, B. Lassalle-Kaiser, J. E. Rault, M. Simon i A. Shukla. "The GALAXIES beamline at the SOLEIL synchrotron: inelastic X-ray scattering and photoelectron spectroscopy in the hard X-ray range". Journal of Synchrotron Radiation 22, nr 1 (1.01.2015): 175–79. http://dx.doi.org/10.1107/s160057751402102x.

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The GALAXIES beamline at the SOLEIL synchrotron is dedicated to inelastic X-ray scattering (IXS) and photoelectron spectroscopy (HAXPES) in the 2.3–12 keV hard X-ray range. These two techniques offer powerful complementary methods of characterization of materials with bulk sensitivity, chemical and orbital selectivity, resonant enhancement and high resolving power. After a description of the beamline components and endstations, the beamline capabilities are demonstrated through a selection of recent works both in the solid and gas phases and using either IXS or HAXPES approaches. Prospects for studies on liquids are discussed.

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Yagoub, Mubarak Y. A., Hendrik C. Swart i Elizabeth Coetsee. "Bulk and surface chemical compositions and microstructure properties of CaF₂:Y³⁺ material". Journal of Vacuum Science & Technology B 41, nr 1 (styczeń 2023): 014001. http://dx.doi.org/10.1116/6.0002279.

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The structural and chemical compositions of Y3+ ion-doped CaF2 were investigated as a possible lanthanide hosting material. A series of CaF2 nanomaterials doped with various concentrations of Y3+ ions under the chelating agent ethylene diamine tetraacetic acid (EDTA) were synthesized using the hydrothermal method. The x-ray diffraction results demonstrated that a mixture of cubic CaF2 and [CaY]F2 phases gradually formed with an increasing Y3+ ion concentration. A single [CaY]F2 cubic phase was formed when EDTA was added as the chelating agent. Scanning electron microscopy results demonstrated that the particle size and the morphology of the material depended on the Y3+ concentration and that EDTA (0.5 g) produced a spherical morphology. The surface and bulk chemical compositions were determined using a combined system of soft x-ray photoemission spectroscopy (XPS) (Al-Kα 1486.7 eV) and hard x-ray photoemission spectroscopy (HAXPES) (Cr-Kα 5414.7 eV). The relative changes in the chemical composition of the surface and subsurface/bulk were investigated. The combined XPS-HAXPES analysis demonstrated that the surface impurities in the accessible peaks (Ca 2p, Y 3d, and F 1s) completely diminished in the subsurface region. However, XPS-HAXPES analysis confirmed that the composition of the [CaY]F2 nanomaterial on the surface differs from that in the subsurface region.

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Cant, David J. H., Benjamen P. Reed, Ben F. Spencer, Wendy R. Flavell i Alexander G. Shard. "Magic angle HAXPES". Journal of Electron Spectroscopy and Related Phenomena 264 (kwiecień 2023): 147311. http://dx.doi.org/10.1016/j.elspec.2023.147311.

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Takagi, Yasumasa, Heng Wang, Yohei Uemura, Takahiro Nakamura, Liwei Yu, Oki Sekizawa, Tomoya Uruga i in. "In situ study of oxidation states of platinum nanoparticles on a polymer electrolyte fuel cell electrode by near ambient pressure hard X-ray photoelectron spectroscopy". Physical Chemistry Chemical Physics 19, nr 8 (2017): 6013–21. http://dx.doi.org/10.1039/c6cp06634h.

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Sato, Shunsuke, Keita Kataoka, Ryosuke Jinnouchi, Naoko Takahashi, Keita Sekizawa, Kousuke Kitazumi, Eiji Ikenaga, Ryoji Asahi i Takeshi Morikawa. "Band bending and dipole effect at interface of metal-nanoparticles and TiO2 directly observed by angular-resolved hard X-ray photoemission spectroscopy". Physical Chemistry Chemical Physics 20, nr 16 (2018): 11342–46. http://dx.doi.org/10.1039/c8cp00551f.

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Siegbahn, Kai. "Preface to hard X-ray photo electron spectroscopy (HAXPES)". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 547, nr 1 (lipiec 2005): 1–7. http://dx.doi.org/10.1016/j.nima.2005.05.007.

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Chaveanghong, Suwilai, Takahiro Nakamura, Yasumasa Takagi, Benjamin Cagnon, Tomoya Uruga, Mizuki Tada, Yasuhiro Iwasawa i Toshihiko Yokoyama. "Sulfur poisoning of Pt and PtCo anode and cathode catalysts in polymer electrolyte fuel cells studied by operando near ambient pressure hard X-ray photoelectron spectroscopy". Physical Chemistry Chemical Physics 23, nr 6 (2021): 3866–73. http://dx.doi.org/10.1039/d0cp06020h.

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We have investigated the S adsorption behaviours on Pt and Pt₃Co anode and cathode electrode catalysts in PEFC under working conditions for the fresh and degraded states, by studying near ambient pressure HAXPES.

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Bouttemy, Muriel, Solène Béchu, Ben F. Spencer, Pia Dally, Patrick Chapon i Arnaud Etcheberry. "Combined Pulsed RF GD-OES and HAXPES for Quantified Depth Profiling through Coatings". Coatings 11, nr 6 (11.06.2021): 702. http://dx.doi.org/10.3390/coatings11060702.

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Chemical characterization at buried interfaces is a real challenge, as the physico-chemical processes operating at the interface govern the properties of many systems and devices. We have developed a methodology based on the combined use of pulsed RF GD-OES (pulsed Radio Frequency Glow Discharge Optical Emission Spectrometry) and XPS (X-ray Photoelectron Spectroscopy) to facilitate the access to deeply buried locations (taking advantage of the high profiling rate of the GD-OES) and perform an accurate chemical diagnosis using XPS directly inside the GD crater. The reliability of the chemical information is, however, influenced by a perturbed layer present at the surface of the crater, hindering traditional XPS examination due to a relatively short sampling depth. Sampling below the perturbed layer may, however, can be achieved using a higher energy excitation source with an increased sampling depth, and is enabled here by a new laboratory-based HAXPES (Hard X-ray PhotoElectron Spectroscopy) (Ga-Kα, 9.25 keV). This new approach combining HAXPES with pulsed RF GD-OES requires benchmarking and is here demonstrated and evaluated on InP. The perturbed depth is estimated and the consistency of the chemical information measured is demonstrated, offering a new route for advanced chemical depth profiling through coatings and heterostructures.

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Pal, Banabir, Sumanta Mukherjee i D. D. Sarma. "Probing complex heterostructures using hard X-ray photoelectron spectroscopy (HAXPES)". Journal of Electron Spectroscopy and Related Phenomena 200 (kwiecień 2015): 332–39. http://dx.doi.org/10.1016/j.elspec.2015.06.005.

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Kokko, Kalevi, Sasuma Granroth, M. H. Heinonen, R. E. Perälä, T. Kilpi, Edwin Kukk, M. P. J. Punkkinen i in. "Atomistic Study of Surfaces and Interfaces of Fe-Cr and Fe-Cr-Al Alloys". Materials Science Forum 762 (lipiec 2013): 728–33. http://dx.doi.org/10.4028/www.scientific.net/msf.762.728.

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Surface and interface properties of Fe-Cr, Fe-Al, and Fe-Cr-Al are studied using Exact Muffin-Tin Orbitals and Monte Carlo methods and with x-ray photoelectron and Auger electron techniques. Surface composition is investigated as a function of oxidation (heating) time. Hard x ray photoelectron spectroscopy (HAXPES) is used to scan non destructively the compositions below the surface. It is found that Cr boosts the Al segregation to the surface.

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Jagannath, U. K. Goutam, R. K. Sharma, J. Singh, K. Dutta, U. S. Sule, R. Pradeep i S. C. Gadkari. "HAXPES beamline PES-BL14 at the Indus-2 synchrotron radiation source". Journal of Synchrotron Radiation 25, nr 5 (2.08.2018): 1541–47. http://dx.doi.org/10.1107/s1600577518008408.

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The Hard X-ray Photo-Electron Spectroscopy (HAXPES) beamline (PES-BL14), installed at the 1.5 T bending-magnet port at the Indian synchrotron (Indus-2), is now available to users. The beamline can be used for X-ray photo-emission electron spectroscopy measurements on solid samples. The PES beamline has an excitation energy range from 3 keV to 15 keV for increased bulk sensitivity. An in-house-developed double-crystal monochromator [Si (111)] and a platinum-coated X-ray mirror are used for the beam monochromatization and manipulation, respectively. This beamline is equipped with a high-energy (up to 15 keV) high-resolution (meV) hemispherical analyzer with a microchannel plate and CCD detector system with SpecsLab Prodigy and CasaXPS software. Additional user facilities include a thin-film laboratory for sample preparation and a workstation for on-site data processing. In this article, the design details of the beamline, other facilities and some recent scientific results are described.

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Fujiwara, Hidenori, Sho Naimen, Atsushi Higashiya, Yuina Kanai, Hiroshi Yomosa, Kohei Yamagami, Takayuki Kiss i in. "Polarized hard X-ray photoemission system with micro-positioning technique for probing ground-state symmetry of strongly correlated materials". Journal of Synchrotron Radiation 23, nr 3 (1.04.2016): 735–42. http://dx.doi.org/10.1107/s1600577516003003.

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An angle-resolved linearly polarized hard X-ray photoemission spectroscopy (HAXPES) system has been developed to study the ground-state symmetry of strongly correlated materials. The linear polarization of the incoming X-ray beam is switched by a transmission-type phase retarder composed of two diamond (100) crystals. The best value of the degree of linear polarization was found to be −0.96, containing a vertical polarization component of 98%. A newly developed low-temperature two-axis manipulator enables easy polar and azimuthal rotations to select the detection direction of photoelectrons. The lowest temperature achieved was 9 K, offering the chance to access the ground state even for strongly correlated electron systems in cubic symmetry. A co-axial sample monitoring system with long-working-distance microscope enables the same region on the sample surface to be measured before and after rotation. Combining this sample monitoring system with a micro-focused X-ray beam by means of an ellipsoidal Kirkpatrick–Baez mirror (25 µm × 25 µm FWHM), polarized valence-band HAXPES has been performed on NiO for voltage application as resistive random access memory to demonstrate the micro-positioning technique and polarization switching.

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Yamashita, Yoshiyuki, Jun Nara, Efi Dwi Indari, Takahiro Yamasaki, Takahisa Ohno i Ryu Hasunuma. "Experimental and theoretical studies on atomic structures of the interface states at SiO₂/4H-SiC(0001) interface". Journal of Applied Physics 131, nr 21 (7.06.2022): 215303. http://dx.doi.org/10.1063/5.0093267.

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We investigated the atomic structures of the interface states (gap states) at the SiO2/4H-SiC(0001) interface using hard x-ray photoelectron spectroscopy (HAXPES), operando hard x-ray photoelectron spectroscopy, extended x-ray absorption fine structure, and first principles molecular dynamics (FPMD) calculations. For the interface states, two types were observed: continuous interface states in the whole gap and interface states with discrete energy levels near the conduction band minimum (CBM). From HAXPES, we found that carbon clusters and carbon vacancies were formed at the SiO2/4H-SiC(0001) interface. FPMD calculations on the SiO2/4H-SiC(0001) interface showed that the interface states in the whole gap were attributed to the various atomic geometries of the CßSi3 species and the carbon clusters with various sizes and surrounding atoms. For the interface states with a discrete energy level near the CBM, we could not find their atomic structure using our current calculations. We calculated the carbon vacancies prepared on the side of an SiC substrate at the SiO2/4H-SiC(0001) interface, indicating the formation of a discrete energy level in the midgap. It is likely that carbon vacancies formed at the step of the interface may modulate the midgap energy level to energy below the CBM. Therefore, we propose that the interface states with discrete energy levels near the CBM could be attributed to the carbon vacancies formed on the steps at the SiO2/4H-SiC(0001) interface.

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Iwama, Tsukasa, Tsuyoshi Ohnishi i Takuya Masuda. "Operando Hard X-Ray Photoelectron Spectroscopy for Observing Interfacial Electrochemical Reactions in All-Solid-State Batteries". ECS Meeting Abstracts MA2023-01, nr 4 (28.08.2023): 864. http://dx.doi.org/10.1149/ma2023-014864mtgabs.

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All-solid-state lithium-ion batteries (ASS-LIBs) have been attracting wide attention for their potential superior performance, such as high safety and long cycle life compared with the conventional lithium-ion batteries with liquid organic electrolytes. However, one of the critical problems of the ASS-LIBs for wide spread applications, especially for electric vehicles, is the large interfacial resistance across the electrode/solid electrolyte (SE)1. When an electrode and SE come into contact, some mobile ions are redistributed at the interface according to their potential difference2,3. In addition, the distribution of the mobile ions and electric potential are also changed during the battery operations. Therefore, dynamic observation of their distribution across the electrode/SE interface is essential to identify and control the origin of the interfacial resistance. Hard x-ray photoelectron spectroscopy (HAXPES) is capable of nondestructive analysis of the elemental composition, oxidation states and electronic structure of sample surfaces and interfaces including those buried with over layers at depth > 10 nm[4]. In this study, we developed a laboratory-based operando HAXPES system equipped with a Cr-Kα source (5414.9 eV), which enables angle-resolved measurements of and bias applications to the sample transferred without air-exposure, and applied it to the charging/discharging reactions of a LiCoO2 (LCO) positive electrode deposited on a Li6.6La3Zr1.6Ta0.4O12 (LLZT) solid electrolyte in a half cell configuration. HAXPES measurements were performed while the LCO electrode was electrically grounded to a hemispherical analyzer. The galvanostatic charge/discharge potential profiles exhibited a characteristic plateau due to delithiation of a O3-LiCoO2 at ~3.9 V vs. Li+/Li5. In the Co 2p 3/2 region of the pristine cell, a sharp intense main peak and a broad satellite peak typical to a LCO were observed. At the charged states, however, the main peak was asymmetrically broadened to the higher binding energy. The main peak was deconvoluted into two peaks at 780 eV and ~781 eV, corresponding to Co3+ ions and Co4+ ions, respectively. The full width half maximums (FWHMs) of the Co4+ ions peak increased at charged states, while that of the Co3+ ions peak was remained unchanged. Furthermore, the relative areas of satellite peak decreased at the charged states. These results suggest that Co3+ ions were oxidized to the Co4+ ions by delithiation of the LCO electrode6,7. After the subsequent discharging, the component of higher binding energy of the main peaks decreased, and the satellite peak increased. In addition, the FWHMs of the Co4+ ions peak decreased, suggesting that the Co4+ ions were reduced by lithiation into the LCO electrode during discharging. Thus, the lithiation/delithiation of LCO was successfully observed by operando HAXPES. References N. Ohta, K. Takada, L. Zhang, R. Ma, M. Osada and T. Sasaki, Advanced Materials, 18, 2226 (2006) K. Yamamoto, Y. Iriyama, T. Asaka, T. Hirayama, H. Fujita, C. A. Fisher, K. Nonaka, Y. Sugita and Z. Ogumi, Angew Chem Int Ed Engl, 49, 4414 (2010) J. Haruyama, K. Sodeyama, L. Han, K. Takada and Y. Tateyama, Chemistry of Materials, 26, 4248 (2014) N. K. F. Curran Kalha, Prajna Bhatt, et al., Journal of Physics: Condensed Matter, 33, 233001 (2021) J. N. Reimers and J. R. Dahn, The Electrochemical Society, 139, 2091 (1992) L. Dahéron, R. Dedryvère, H. Martinez, M. Ménétrier, C. Denage, C. Delmas and D. Gonbeau, Chemistry of Materials (2008) H. Kiuchi, K. Hikima, K. Shimizu, R. Kanno, F. Toshiharu and E. Matsubara, Electrochemistry Communications, 118, 106790 (2020)

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AMINO, Naoya, i Kenichi OZAWA. "Applications of Hard X-ray Photoelectron Spectroscopy (HAXPES) to Rubber Materials Developments". NIPPON GOMU KYOKAISHI 92, nr 2 (2019): 76–81. http://dx.doi.org/10.2324/gomu.92.76.

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Panaccione, G., G. Cautero, M. Cautero, A. Fondacaro, M. Grioni, C. Henriquet, G. Monaco i in. "Results and perspectives in hard X-ray photoemission spectroscopy (HAXPES) from solids". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 246, nr 1 (maj 2006): 106–11. http://dx.doi.org/10.1016/j.nimb.2005.12.021.

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Saito, Yoshihiro, Shigeaki Uemura, Tomohiro Kagiyama i Ryo Toyoshima. "XPS and HAXPES analyses for pre-sputtered InP surface and InP/Pt interface". Japanese Journal of Applied Physics 61, nr 3 (1.03.2022): 031005. http://dx.doi.org/10.35848/1347-4065/ac55e6.

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Abstract The state of the pre-sputtered indium phosphide (InP) surface was analyzed by X-ray photoelectron spectroscopy, employing synchrotron-based relatively low-energy X-ray. It was found that the pre-sputtering treatment induced the phosphorus vaporization and made the surface composition In-rich, which was thought to promote oxidation of InP surface in atmosphere. The state of the interface between InP and Pt was also investigated nondestructively, by using hard X-ray photoemission spectroscopy. As a result, it was demonstrated that the interfacial layer was composed of the native oxide (In–O, P–O) and metallic state (In–Pt or In–In, P–P) and that the pre-sputtering treatment increased significantly the amount of the P–O, In–Pt or In–In, and P–P. From a simplified calculation, assuming a Pt/In–Pt/In–P layer stacking structure and neglecting the In–O and P–O components, the thickness of the interfacial layer was estimated to be approximately 3.0 nm.

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BADÍA-ROMANO, L., J. RUBÍN, F. BARTOLOMÉ, J. BARTOLOMÉ, S. OVCHINNIKOV, S. VARNAKOV, C. MAGÉN, J. RUBIO-ZUAZO i G. R. CASTRO. "MORPHOLOGICAL AND COMPOSITIONAL STUDY AT THE Si/Fe INTERFACE OF (Fe/Si) MULTILAYER". SPIN 04, nr 01 (marzec 2014): 1440002. http://dx.doi.org/10.1142/s2010324714400025.

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Diffusion and reaction of elements at the interfaces of nanostructured systems play an important role in controlling their physical and chemical properties for subsequent applications. ( Fe / Si ) nanolayers were prepared by thermal evaporation under ultrahigh vacuum onto a Si (100) substrate. A morphological characterization of these films was performed by combination of scanning transmission electron microscopy (STEM) and X-ray reflectivity (XRR). The compositional depth profile of the ( Fe / Si ) structures was obtained by angle resolved X-ray photoelectron spectroscopy (ARXPS) and hard X-ray photoelectron spectroscopy (HAXPES). Moreover, determination of the stable phases formed at the Si on Fe interfaces was performed using conversion electron Mössbauer spectroscopy. The Si / Fe interface thickness and roughness were determined to be 1.4 nm and 0.6 nm, respectively. A large fraction of the interface is composed of c- Fe 1-x Si paramagnetic phase, though a minoritary ferromagnetic Fe rich silicide phase is also present.

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Woicik, J. C., D. A. Fischer, E. Vescovo, D. A. Arena, D. E. Starr, B. O. Wells i C. S. Fadley. "International Workshop for New Opportunities in Hard X-ray Photoelectron Spectroscopy: HAXPES 2009". Synchrotron Radiation News 23, nr 1 (2.02.2010): 19–21. http://dx.doi.org/10.1080/08940880903547306.

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Sachs, Malte, Michael Gellert, Min Chen, Hans-Jörg Drescher, Stefan Renato Kachel, Han Zhou, Malte Zugermeier, Mihaela Gorgoi, Bernhard Roling i J. Michael Gottfried. "LiNi0.5Mn1.5O4 high-voltage cathode coated with Li4Ti5O12: a hard X-ray photoelectron spectroscopy (HAXPES) study". Physical Chemistry Chemical Physics 17, nr 47 (2015): 31790–800. http://dx.doi.org/10.1039/c5cp03837e.

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A Li₄Ti₅O₁₂ coated LiNi_0.5Mn_1.5O₄ high-voltage cathode was depth profiled by hard X-ray photoelectron spectroscopy after electrochemical cycling.

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Kövér, László. "Energy loss structures in HAXPES spectra of solids". Journal of Electron Spectroscopy and Related Phenomena 190 (październik 2013): 144–52. http://dx.doi.org/10.1016/j.elspec.2013.04.002.

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Weinhardt, Lothar, Ralph Steininger, Dagmar Kreikemeyer-Lorenzo, Stefan Mangold, Dirk Hauschild, David Batchelor, Thomas Spangenberg i Clemens Heske. "X-SPEC: a 70 eV to 15 keV undulator beamline for X-ray and electron spectroscopies". Journal of Synchrotron Radiation 28, nr 2 (10.02.2021): 609–17. http://dx.doi.org/10.1107/s1600577520016318.

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X-SPEC is a high-flux spectroscopy beamline at the KIT (Karlsruhe Institute of Technology) Synchrotron for electron and X-ray spectroscopy featuring a wide photon energy range. The beamline is equipped with a permanent magnet undulator with two magnetic structures of different period lengths, a focusing variable-line-space plane-grating monochromator, a double-crystal monochromator and three Kirkpatrick–Baez mirror pairs. By selectively moving these elements in or out of the beam, X-SPEC is capable of covering an energy range from 70 eV up to 15 keV. The flux of the beamline is maximized by optimizing the magnetic design of the undulator, minimizing the number of optical elements and optimizing their parameters. The beam can be focused into two experimental stations while maintaining the same spot position throughout the entire energy range. The first experimental station is optimized for measuring solid samples under ultra-high-vacuum conditions, while the second experimental station allows in situ and operando studies under ambient conditions. Measurement techniques include X-ray absorption spectroscopy (XAS), extended X-ray absorption fine structure (EXAFS), photoelectron spectroscopy (PES) and hard X-ray PES (HAXPES), as well as X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS).

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Oura, Masaki, Tatsuya Wagai, Ashish Chainani, Jun Miyawaki, Hiromi Sato, Masaharu Matsunami, Ritsuko Eguchi i in. "Development of a single-shot CCD-based data acquisition system for time-resolved X-ray photoelectron spectroscopy at an X-ray free-electron laser facility". Journal of Synchrotron Radiation 21, nr 1 (10.12.2013): 183–92. http://dx.doi.org/10.1107/s1600577513028233.

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In order to utilize high-brilliance photon sources, such as X-ray free-electron lasers (XFELs), for advanced time-resolved photoelectron spectroscopy (TR-PES), a single-shot CCD-based data acquisition system combined with a high-resolution hemispherical electron energy analyzer has been developed. The system's design enables it to be controlled by an external trigger signal for single-shot pump–probe-type TR-PES. The basic performance of the system is demonstrated with an offline test, followed by online core-level photoelectron and Auger electron spectroscopy in `single-shot image', `shot-to-shot image (image-to-image storage or block storage)' and `shot-to-shot sweep' modes at soft X-ray undulator beamline BL17SU of SPring-8. In the offline test the typical repetition rate for image-to-image storage mode has been confirmed to be about 15 Hz using a conventional pulse-generator. The function for correcting the shot-to-shot intensity fluctuations of the exciting photon beam, an important requirement for the TR-PES experiments at FEL sources, has been successfully tested at BL17SU by measuring Au 4fphotoelectrons with intentionally controlled photon flux. The system has also been applied to hard X-ray PES (HAXPES) in `ordinary sweep' mode as well as shot-to-shot image mode at the 27 m-long undulator beamline BL19LXU of SPring-8 and also at the SACLA XFEL facility. The XFEL-induced Ti 1score-level spectrum of La-doped SrTiO3is reported as a function of incident power density. The Ti 1score-level spectrum obtained at low power density is consistent with the spectrum obtained using the synchrotron source. At high power densities the Ti 1score-level spectra show space-charge effects which are analysed using a known mean-field model for ultrafast electron packet propagation. The results successfully confirm the capability of the present data acquisition system for carrying out the core-level HAXPES studies of condensed matter induced by the XFEL.

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Medjanik, K., S. V. Babenkov, S. Chernov, D. Vasilyev, B. Schönhense, C. Schlueter, A. Gloskovskii i in. "Progress in HAXPES performance combining full-field k-imaging with time-of-flight recording". Journal of Synchrotron Radiation 26, nr 6 (1.11.2019): 1996–2012. http://dx.doi.org/10.1107/s1600577519012773.

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An alternative approach to hard-X-ray photoelectron spectroscopy (HAXPES) has been established. The instrumental key feature is an increase of the dimensionality of the recording scheme from 2D to 3D. A high-energy momentum microscope detects electrons with initial kinetic energies up to 8 keV with a k-resolution of 0.025 Å−1, equivalent to an angular resolution of 0.034°. A special objective lens with k-space acceptance up to 25 Å−1 allows for simultaneous full-field imaging of many Brillouin zones. Combined with time-of-flight (ToF) parallel energy recording this yields maximum parallelization. Thanks to the high brilliance (1013 hν s−1 in a spot of <20 µm diameter) of beamline P22 at PETRA III (Hamburg, Germany), the microscope set a benchmark in HAXPES recording speed, i.e. several million counts per second for core-level signals and one million for d-bands of transition metals. The concept of tomographic k-space mapping established using soft X-rays works equally well in the hard X-ray range. Sharp valence band k-patterns of Re, collected at an excitation energy of 6 keV, correspond to direct transitions to the 28th repeated Brillouin zone. Measured total energy resolutions (photon bandwidth plus ToF-resolution) are 62 meV and 180 meV FWHM at 5.977 keV for monochromator crystals Si(333) and Si(311) and 450 meV at 4.0 keV for Si(111). Hard X-ray photoelectron diffraction (hXPD) patterns with rich fine structure are recorded within minutes. The short photoelectron wavelength (10% of the interatomic distance) `amplifies' phase differences, making full-field hXPD a sensitive structural tool.

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Favaro, Marco, Pip C. J. Clark, Micheal J. Sear, Martin Johansson, Sven Maehl, Roel van de Krol i David E. Starr. "Spectroscopic analysis with tender X-rays: SpAnTeX, a new AP-HAXPES end-station at BESSY II". Surface Science 713 (listopad 2021): 121903. http://dx.doi.org/10.1016/j.susc.2021.121903.

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Rubio-Zuazo, J. R., i G. R. Castro. "Hard X-ray photoelectron spectroscopy (HAXPES) (⩽15keV) at SpLine, the Spanish CRG beamline at the ESRF". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 547, nr 1 (lipiec 2005): 64–72. http://dx.doi.org/10.1016/j.nima.2005.05.013.

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Fondell, M., M. Gorgoi, M. Boman i A. Lindblad. "An HAXPES study of Sn, SnS, SnO and SnO 2". Journal of Electron Spectroscopy and Related Phenomena 195 (sierpień 2014): 195–99. http://dx.doi.org/10.1016/j.elspec.2014.07.012.

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Yu, Yang, Karl F. Ludwig, Srikanth Gopalan, Uday Bhanu Pal i Soumendra Nath Basu. "Role of Strain in Surface Segregation of La_1-XSr_xCo_0.2Fe_0.8O₃". ECS Meeting Abstracts MA2018-01, nr 32 (13.04.2018): 1936. http://dx.doi.org/10.1149/ma2018-01/32/1936.

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Strontium doped lanthanum cobalt ferrite (LSCF), a widely used cathode material in solid oxide fuel cells (SOFC), can have long-term stability issues that can adversely affect electrochemical performance. Heteroepitaxial thin films of La1-x SrxCo0.2Fe0.8O3 with varying Sr content (x = 0.4, 0.3, 0.2) were deposited on single crystal NdGaO3, SrTiO3 and GdScO3 substrates by pulsed laser deposition. The lattice mismatch between the films and the substrate led to different strains in the films. The extent of Sr-rich precipitate formation on the film surface was quantified using total reflection X-ray fluorescence (TXRF), and atomic force microscopy (AFM). The microstructure and the nature of the bonding of the surface Sr-rich phases were investigated by scanning/transmission electron microscopy (S/TEM) and hard x-ray photoelectron spectroscopy (HAXPES), respectively. The strain in the thin films was measured by high-resolution x-ray diffraction (HRXRD). The combined effects of the strontium content and strain on the extent of surface phase formation will be discussed.

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Favaro, Marco. "(Invited) In Situ Photoelectron Spectroscopy Reveals the Chemical Nature of Semiconductor Surface States". ECS Meeting Abstracts MA2023-02, nr 48 (22.12.2023): 2434. http://dx.doi.org/10.1149/ma2023-02482434mtgabs.

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The accessible photovoltage of semiconducting photoabsorbers is typically 0.5-1 V below the theoretically achievable values predicted by the Shockley-Queisser limit [1]. Although the reason for this is still not well understood, surface and interface states within the photoabsorbers energy band gap may play a crucial role as they generally induce Fermi level pinning [2]. Within the PEC community, two key elements have been identified for the maximization of the photovoltage in photoelectrodes for water splitting: (i) the passivation of surface defects which is needed to avoid Fermi level pinning, and (ii) the increase of the minority carrier concentration at the interface to improve contact selectivity and optimize carrier extraction [3,4]. To understand the role of surface defects on Fermi level pinning, detailed information on the chemical nature and electronic properties of surface states is needed. Such information is usually obtained with UHV surface science techniques such as XPS, but the photoelectrode surface under UHV conditions has little, if any, relevance to the electrified surface when immersed in the electrolyte. Moreover, recent studies have shown that semiconductor surfaces are not static, but undergo extensive structural and chemical transformations during PEC device operation [5,6]. In this talk, we will show our recent development of state-of-the-art techniques to study the structure and dynamics of semiconductor/water interfaces under practically relevant conditions [7]. The chemical nature of the electronic states for selected semiconductors prepared at the Institute for Solar Fuels has been explored using synchrotron-based resonant, ambient pressure soft and hard X-ray photoelectron spectroscopy (AP-XPS and AP-HAXPES) [6,8-11], and with in situ/operando Raman and photoluminescence spectroscopy. In particular, we will show that it is possible to study photon-induced chemical changes at solid/liquid interfaces using AP-XPS and AP-HAXPES [6,8]. We will conclude this contribution by discussing about future perspectives and technical implementations for multimodal in situ/operando investigations of photoelectrocatalytic processes. [1] M.T. Mayer. Curr. Opin. Electrochem. 2017, 2, 104. [2] A. J. Bard et al. J. Am. Chem. Soc. 1980, 102, 3671. [3] A.G. Scheuermann et al., Nat. Mater. 2016, 15, 99. [4] M. Schleuning et al., Sustainable Energy Fuels, 2022, 6, 3701. [5] F.M. Toma et al., Nat. Commun. 2016, 7, 12012. [6] M. Favaro et al., J. Phys. Chem. B 2018, 122, 801. [7] M. Favaro et al., Surf. Sci. 2021, 713, 121903. [8] M. Favaro et al., J. Phys. D: Appl. Phys. 2021, 54, 164001. [9] M. Favaro et al., J. Phys. Chem. C 2019, 123, 8347. [10] W. Wang et al., J. Am. Chem. Soc. 2022, 144, 17173. [11] P. Schnell et al., Sol. RRL 2023, 2201104.

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Nagata, Takahiro, Somu Kumaragurubaran, Kenichiro Takahashi, Sung-Gi Ri i Toyohiro Chikyow. "(Invited) Combinatorial Synthesis and Interface Analysis for Development of High Dielectric Constant Thin Films". ECS Meeting Abstracts MA2022-01, nr 19 (7.07.2022): 1070. http://dx.doi.org/10.1149/ma2022-01191070mtgabs.

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Compound semiconductor-based power devices such as SiC and GaN require high-temperature operational passive devices such as a capacitor. SiC based active devices are capable of operating over 250°C. For module and system level advancement, the high-temperature operational passive should be developed urgently. In the case of capacitors, current available capacitors can efficiently function up to 175°C only. Therefore, a thin film capacitor that can be operated at high-temperatures and integrated monolithically in the proximity of active device should be developed. In this talk, I will introduce our achievements of development of high temperature operational dielectric film materials and its interface control of metal/oxide stacking structure mainly. By employing combinatorial method and the thermal diffusion theory, we found some candidates for the dielectric materials based on ferroelectric materials. The BaTiO3 based relaxor ferroelectrics with a high dielectric constant (> 200) and free of hazardous elements are promising candidates. Among the BaTiO3 based relaxor ferroelectrics, we have chosen x[BaTiO3]-(1-x)[Bi(Mg2/3Nb1/3)O3] (BT-BMN). The permittivity of 400 and the stability <8% from room temperature to 400°C has been obtained, which are promising as a high-temperature dielectric medium. For the practical device application, a thermal stable electrode on the dielectrics is also required. To control the interface stability of the electrode/BT-BMN interfaces, several electrodes were investigated by photoelectron spectroscopy (PES). From the viewpoints of the oxidization energy, cost, and Bi thermal diffusion energy, RuO2, TiC, and TaC were selected as the electrode candidates to compare with the Pt electrode. To probe the interface structure and the band alignment non-destructively, we employed a combination of conventional x-ray PES using Al Kα light source (SXPES: hν= 1486.6 eV) and hard x-ray PES (HAXPES, hν= 5.95 keV). HAXPES is a powerful tool for investigating heterostructure interfaces due to its longer inelastic mean free path (IMFP) than that of SXPES. The IMFP of Pt 4f7/2, which was the heaviest element with the shortest IMFP in our measurement, was 4.68 nm, and HAXPES probed approximately 15 nm (probing depth: 3×IMFP) below the surface. For the Pt electrode, which is usually used as an electrode for Bi-contained oxides, the Bi diffusion into the electrode layer and the change of band alignment were clearly observed after annealing at 400°C. In contrast, the TiC electrode inhibited the Bi diffusion and did not show any change of the band alignment after annealing, meaning that the TiC electrode is a potential candidate for the electrode of Bi-contained oxide for high temperature operational devices. In the presentation, we also introduce the development of new high-k gate materials for GaN and Ge channels by combining the combinatorial method and HAXPES analysis. For a Ge channel, which has been attracting a lot of attention as a replacement for the Si channel used in current Si-based metal-oxide-semiconductor (CMOS) devices. This is because the Ge channel has high electron and hole mobility, which lead to a higher drive current, and Ge has a narrower band gap than Si thus allowing supply voltage scaling. However, Ge has the same issue as Si, namely an unintentionally oxidized layer with a low dielectric constant (~5.6) can form at an oxide/Ge interface. Furthermore, in contrast with SiO2, which is a good insulating layer for MOS devices, GeOx is thermodynamically unstable and water soluble. These properties cause high defect densities at the interface between high-k and Ge and a large hysteresis in the capacitance-voltage characteristic. To overcome these issues, we have proposed the direct growth of (110) rutile TiO2 or non-oxide materials on (100) Ge substrates.

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Matsumoto, Masashi, Masazumi Arao, Shota Katayama, Shiori Kudo, Takahiko Asaoka, Yoichiro Tsuji, Yoshiharu Sakurai, Yoshiharu Uchimoto i Hideto Imai. "Multi-Modal Structure and Distribution Analysis of Functional Groups on Carbon Supports for Polymer-Electrolyte Fuel Cells". ECS Meeting Abstracts MA2023-02, nr 37 (22.12.2023): 1745. http://dx.doi.org/10.1149/ma2023-02371745mtgabs.

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Although structures of the functional groups formed on the surface of the carbon supports and their distribution on/inside supports have crucial impacts on determining performance of the catalyst electrodes, understanding of the relationship between them remains unclear, because of limitation of experimental methods for quantitative analysis of them with high spatial resolution. It is well-known that functional groups of the catalyst supports affect chemical properties of the supports, such as, redox- and acid-base properties, hydrophobicity, and electronic interaction. Thus, they should have a great influence on various aspects those related to the performance of polymer electrolyte fuel cell (PEFC), such as the activity, mass transportability, and durability of the catalysts and catalyst layers, and manufacturing process of catalysts and catalyst layer. 1,2). Furthermore, recently, in addition to various conventional high-surface area carbon supports, such as, Vulcan and Ketjen black, accessible carbon supports with mesopores which can host Pt particles protects them from direct ionomer adsorption and allow proton and O2 to have reasonable access to Pt particles, have been attracting great attention for improving catalyst utilization, activity, mass transportability, and suppression of Pt dissolution 3-5). The relationship between structure variation of functional groups on various supports and electrode performances should be of interest. The major difficulty for analyzing the functional groups on carbon supports come from the structure complexity of carbon surface (as well as inner part of the carbon particles), inhomogeneous distribution of various functional groups produced in various chemical processes, and multi-component structure of catalyst electrodes with catalysts and ionomers. Against such background, in this study, we have developed a new experimental approach utilizing multi-modal analysis method with x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), temperature-programmed-desorption mass spectroscopy (TPD-MS), vibrational spectroscopy, electron tomography (3D-TEM), and cryo transmission electron microscopy (cryo-TEM). By combining suitable experimental probes for each structural feature and each component in multi-component structures, and by analyzing in integrated manner, we are able to understand the complex structure of functional groups on and inside carbon supports. Here, we demonstrate an example of the analysis for Vulcan (VULCAN® XC72, Cabot Corporation) and Pt-supported Vulcan (TEC10V30E, Tanaka Kikinnzoku Kogyo K. K. ). Vulcan is a solid carbon support used for polymer electrolyte fuel cell catalysts. The sample was reduced for about 30 minutes in a 100% hydrogen atmosphere at room temperature. Hard x-ray photoelectron spectroscopy (HAXPES) using synchrotron radiation x-rays with x-ray energy of 8 keV (BL46XU at SPring-8) . Also soft X-ray XAS were performed on BL1N2 at Aichi SR . Figure 1 shows the C1s HAXPES spectrum and the C K-edge XANES spectrum acquired by total electron yield (TEY) method. HAXPES was normalized by the signal intensity of the C-C substrate components (sp2, sp3) of the support at 284.5 eV 6), whereas the C K-edge XANES is normalized by the signal intensity of the 2pz (π*) orbital extending perpendicular to the carbon hexagonal network plane of the C–C substrate component of the support at 285.2 eV 7, 8). The functional groups are clearly observed in both spectra and the signal intensity of the functional group of the Pt catalyst increased with respect to the support alone, indicating that the amount of functional group on the support increased due to the Pt loading process. By combining other experimental results and theoretical simulations, the relationship between structure properties and electrode performance can be discussed. Acknowledgement This work was conducted in FC-Platform project supported by the New Energy and Industrial Technology Development Organization (NEDO). References : 1) E. Antolini, Applied Catalysis B: Environmental 88, 1 (2009) 2) Y.-J. Wang, N. Zhao, B. Fang, H. Li, X. T. Bi, and H. Wang, Chem Rev 115, 3433 (2015) 3)V. Yarlagadda, M. K. Carpenter, T. E. Moylan, R. S. Kukreja, R. Koestner, W. Gu, L. Thompson, and A. Kongkanand, ACS Energy Letters 3, 618 (2018) 4)S. Ott, A. Orfanidi, H. Schmies, B. Anke, H. N. Nong, J. Hübner, U. Gernert, M. Gliech, M. Lerch and P. Strasser , Nature Mater., 19, 77 (2020) 5)A. Kobayash, T. Fujii, C. Harada, E. Yasumoto, K. Takeda, K. Kakinuma, and M. Uchida, Acs Appl. Energy Mater. 4 2307 (2021) 6) S. Kundu, Y. Wang, W. Xia, and M. Muhler, J. Phys. Chem. C, 112, 16869 (2008) 7) Y. Murakami, Y. Ota, and T. Okada, Anal. Sci., 39, 67 (2023) 8) C. L. Guillou, S. Bernard. F. de la Pena, and Y. L. Brech, Anal. Chem., 90, 8379 (2018) Figure 1

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Young, Benjamin T., David R. Heskett, Cao Cuong Nguyen, Mengyun Nie, Joseph C. Woicik i Brett L. Lucht. "Hard X-ray Photoelectron Spectroscopy (HAXPES) Investigation of the Silicon Solid Electrolyte Interphase (SEI) in Lithium-Ion Batteries". ACS Applied Materials & Interfaces 7, nr 36 (3.09.2015): 20004–11. http://dx.doi.org/10.1021/acsami.5b04845.

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Yamasaki, A., A. Sekiyama, S. Imada, M. Tsunekawa, A. Higashiya, A. Shigemoto i S. Suga. "Bulk sensitive photoelectron spectroscopy with soft and hard X-rays: Soft X-ray ARPES toward high resolution HAXPES". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 547, nr 1 (lipiec 2005): 136–50. http://dx.doi.org/10.1016/j.nima.2005.05.019.

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Kalha, C., M. Reisinger, P. K. Thakur, T. L. Lee, S. Venkatesan, M. Isaacs, R. G. Palgrave, J. Zechner, M. Nelhiebel i A. Regoutz. "Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach". Journal of Applied Physics 131, nr 16 (28.04.2022): 165301. http://dx.doi.org/10.1063/5.0086009.

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Power semiconductor device architectures require the inclusion of a diffusion barrier to suppress or at best prevent the interdiffusion between the copper metallization interconnects and the surrounding silicon substructure. The binary pseudo-alloy of titanium–tungsten (TiW), with >70 at. % W, is a well-established copper diffusion barrier but is prone to degradation via the out-diffusion of titanium when exposed to high temperatures ([Formula: see text]400 [Formula: see text]C). Here, the thermal stability of physical vapor deposited TiW/Cu bilayer thin films in Si/SiO[Formula: see text](50 nm)/TiW(300 nm)/Cu(25 nm) stacks were characterized in response to annealing at 400 [Formula: see text]C for 0.5 h and 5 h, using a combination of soft and hard x-ray photoelectron spectroscopy and transmission electron microscopy. Results show that annealing promoted the segregation of titanium out of the TiW and interdiffusion into the copper metallization. Titanium was shown to be driven toward the free copper surface, accumulating there and forming a titanium oxide overlayer upon exposure to air. Annealing for longer timescales promoted a greater out-diffusion of titanium and a thicker oxide layer to grow on the copper surface. However, interface measurements suggest that the diffusion is not significant enough to compromise the barrier integrity, and the TiW/Cu interface remains stable even after 5 h of annealing.

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Mateo Moreno, Javier, Rodrigo Calvo Membibre, Sergio Pinilla Yanguas, Juan Rubio Zuazo i Miguel Manso Siván. "Montecarlo Simulation and HAXPES Analysis of Organosilane Segregation in Titania Xerogel Films; Towards a Generic Surface Chemofunctionalization Process". Surfaces 3, nr 3 (28.07.2020): 352–65. http://dx.doi.org/10.3390/surfaces3030026.

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The formation of xerogels implies a sequence of hydrolysis and condensation reactions, which are intricate to analyze in heteromolecular sols. We analyze by probabilistic Montecarlo methods the development of hybrid organosilane–titania xerogels and illustrate how partial charges of the reacting molecules can help estimating relative probabilities for the condensation of the molecules. Since the condensation rate of Ti alkoxides is much higher than the corresponding rate of Si alkoxides (especially if bearing a non-hydrolizable group), by imposing a fast condensation process in agreement with low pH kinetics, the process leads to a surface segregation of the organosilane. The simulation results are compared with results of characterization of thin condensates of two different organosilanes within a titanium–isopropoxide matrix. Non-destructive in-depth profiles were obtained by hard x-ray photoelectron spectroscopy, which can resolve through estimation of Si and specific moieties of the organosilane molecules the progress of the condensation. These results are relevant for the generalization of chemo-functionalization processes by kinetic demixing of organosilanes, which have myriad applications in biomedicine and biotechnology.

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Wu, M. Y., Q. S. Huang, K. Le Guen, V. Ilakovac, B. X. Li, Z. S. Wang, A. Giglia, J. P. Rueff i P. Jonnard. "Characterization of Pd/Y multilayers with B4C barrier layers using GIXR and X-ray standing wave enhanced HAXPES". Journal of Synchrotron Radiation 25, nr 5 (9.08.2018): 1417–24. http://dx.doi.org/10.1107/s1600577518009402.

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Pd/Y multilayers are high-reflectance mirrors designed to work in the 7.5–11 nm wavelength range. Samples, prepared by magnetron sputtering, are deposited with or without B4C barrier layers located at the interfaces of the Pd and Y layers to reduce interdiffusion, which is expected from calculating the mixing enthalpy of Pd and Y. Grazing-incident X-ray reflectometry is used to characterize these multilayers. B4C barrier layers are found to be effective in reducing Pd–Y interdiffusion. Details of the composition of the multilayers are revealed by hard X-ray photoemission spectroscopy with X-ray standing wave effects. This consists of measuring the photoemission intensity from the samples by performing an angular scan in the region corresponding to the multilayer period and an incident photon energy according to Bragg's law. The experimental results indicate that Pd does not chemically react with B nor C at the Pd–B4C interface while Y does react at the Y–B4C interface. The formation of Y–B or Y–C chemical compounds could be the reason why the interfaces are stabilized. By comparing the experimentally obtained angular variation of the characteristic photoemission with theoretical calculations, the depth distribution of each component element can be interpreted.

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Abulikemu, Aierxiding, Toshiyuki Matsunaga, Tsuyoshi Takami, Kentaro Yamamoto, Tomoki Uchiyama, Toshiki Watanabe, Miki Inada i Yoshiharu Uchimoto. "Improving the Cyclic Reversibility of Layered Li-Rich Cathodes by Combining Oxygen Vacancies Introduction and Surface Fluorination". ECS Meeting Abstracts MA2023-02, nr 65 (22.12.2023): 3042. http://dx.doi.org/10.1149/ma2023-02653042mtgabs.

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Layered-type Li-rich cathode materials have attracted significant attention for the next generation Li-ion batteries, but their poor reversibility in terms of both voltage and capacity upon cycling are as prominent as their high capacity. Irreversible oxygen redox activity and surface deterioration have been deemed as the root cause and direct cause for their poor performance, respectively. To mitigate those issues, we introduce substantial amounts of oxygen vacancies into layered-type Li1.2Ni0.2Co0.2Mn0.4O2 by using CaH2 as a reduction agent. Reduced samples show higher reversible capacity due to the increased cation redox participation, but still sustain poor cyclic performance. With further fluorination to reduced Li1.2Ni0.2Co0.2Mn0.4O2-x by using NH4HF2, the reversible capacity reached 270 mAh/g and maintained its 99% after 100 cycles. STEM-EELS detects deeper F signals rather than just on surface as direct fluorination methods show, and HAXPES patterns indicate there are both ionic and covalent fluorine coordination. These results demonstrate that by the combination of oxygen deficiency introduction and surface fluorination, some F- ions could occupy the sites of oxygen vacancies near the surface rather than sole LiF generation on the surface, which illuminates a new strategy to modify the cathode materials for Li-ion batteries. The Ni0.2Co0.2Mn0.4(OH)1.6 precursor was prepared by the coprecipitation of NiSO4, CoSO4 and MnSO4, and then mixed with LiOH. The mixture was calcined with oxygen flow at 900 ℃ to obtain pristine Li1.2Ni0.2Co0.2Mn0.4O2. The pristine Li1.2Ni0.2Co0.2Mn0.4O2 was reduced by the appropriate amount of CaH2 in a vacuumed glass tube at 260 ℃, then the reduced Li1.2Ni0.2Co0.2Mn0.4O1.85 was mixed with various amounts of NH4HF2 and sintered at 450 ℃ with argon flow. Hard X-ray photoemission spectroscopy (HAXPES, at BL46XU in SPring-8) was used to investigate the coordination state of fluorine ions. The electrodes of different samples were prepared by slurrying the active material, acetylene black, and PVDF with a weight ratio of 8:1:1, then coating on the Al foil. The 2032-type coin cells were assembled for the electrochemical test. The counter electrode was lithium metal and the electrolyte was 1 M LiPF6 in EC and EMC solvent (3:7 by volume). The charge-discharge test was operated on an automatic cycling and data recording system (HJ1001SD8, Hokuto Denko). Fig. 1a shows the F 1s HAXPES spectra of fluorinated samples which were synthesized by subjecting reduced Li1.2Ni0.2Co0.2Mn0.4O1.85 to chemical fluorination using NH4HF2. When F is 0.1 stoichiometry, F ions are more covalent which implies they could mainly occupy the oxygen vacancy sites near surface. Further fluorination increased the intensity of LiF on surface. The cyclic performance of four samples is shown in Fig. 1b. The pristine sample suffered from the severe capacity decay whose drastic oxygen redox activity is deemed to cause various deterioration [1]. Direct fluorination of pristine sample had some positive effect to the cyclic performance because of the reported interface stabilization [2]. The initial capacity of the reduced sample is higher than pristine sample owing to the increased cation redox contribution, but its cyclability is still poor especially after long cycles. The important point to note is the combination of reduction and fluorination significantly improved both the capacity and cyclic performance upon 100 cycles, and the coordination and role of fluorine ions could be different from the conventional fluorination strategy. Figure 1

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Beni, Alessandra, Noémie Ott, Magdalena Pawelkiewicz, Micheline Wardé, Kirsty Young, Birgitta Bauer, Parasmani Rajput i in. "Hard X-ray Photoelectron Spectroscopy (HAXPES) characterisation of electrochemical passivation oxide layers on Al–Cr–Fe complex metallic alloys (CMAs)". Electrochemistry Communications 46 (wrzesień 2014): 13–17. http://dx.doi.org/10.1016/j.elecom.2014.05.024.

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Thejasiri, S. A. A. B., K. M. D. C. Jayathilaka, F. S. B. Kafi, L. S. R. Kumara, O. Seo, S. Yasuno, O. Sakata, W. Siripala i R. P. Wijesundera. "Cu2O Homojunction Solar Cells: Efficiency Enhancement with a High Short Circuit Current". Coatings 14, nr 8 (25.07.2024): 932. http://dx.doi.org/10.3390/coatings14080932.

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Cu2O homojunction solar cells were fabricated using potentiostatic electrodeposition technique. n-Cu2O thin films were grown in an acetate bath while p-Cu2O thin films were grown in a lactate bath. In the growth of n-Cu2O films, cupric acetate concentration, pH and temperature of the bath, deposition potential and duration (film thickness) and annealing temperature were investigated. In the growth of p-Cu2O on n-Cu2O, concentration of copper sulphate and lactic acid solutions, pH and temperature of the bath, deposition potential and duration were investigated. In addition, the procedure of sulfidation of p-Cu2O film surface using (NH4)2S vapor, before depositing Au front contact, was also optimized to enhance the photoactive performance. The structural, morphological and optoelectronic properties of the Cu2O films were investigated using scanning electron microscopy (SEMs), high energy X-ray diffraction (HEXRD), hard X-ray photoelectron spectroscopy (HAXPES), spectral response and current–voltage (J-V) measurements. The best Cu2O homojunction solar cell exhibited Voc = 460 mV, Jsc = 12.99 mA·cm−2, FF = 42% and η = 2.51%, under AM 1.5 illumination. Efficiency enhancement with the record high Jsc value for the Cu2O homojunction solar cell has mainly been due to the optimization of pH of the n-Cu2O deposition bath and lactic acid concentration of the p-Cu2O deposition bath.

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Borgatti, F., F. Offi, P. Torelli, G. Monaco i G. Panaccione. "Interfacial and bulk electronic properties of complex oxides and buried interfaces probed by HAXPES". Journal of Electron Spectroscopy and Related Phenomena 190 (październik 2013): 228–34. http://dx.doi.org/10.1016/j.elspec.2013.01.002.

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Younesi, Reza, Maria Hahlin, Marcel Treskow, Johan Scheers, Patrik Johansson i Kristina Edström. "Ether Based Electrolyte, LiB(CN)4 Salt and Binder Degradation in the Li–O2 Battery Studied by Hard X-ray Photoelectron Spectroscopy (HAXPES)". Journal of Physical Chemistry C 116, nr 35 (23.08.2012): 18597–604. http://dx.doi.org/10.1021/jp303691m.

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Fondell, M., M. Gorgoi, M. Boman i A. Lindblad. "Surface modification of iron oxides by ion bombardment – Comparing depth profiling by HAXPES and Ar ion sputtering". Journal of Electron Spectroscopy and Related Phenomena 224 (kwiecień 2018): 23–26. http://dx.doi.org/10.1016/j.elspec.2017.09.008.

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Werner, Wolfgang S. M., Werner Smekal, Thomas Hisch, Julia Himmelsbach i Cedric J. Powell. "Simulation of Electron Spectra for Surface Analysis (SESSA)for quantitative interpretation of (hard) X-ray photoelectron spectra(HAXPES)". Journal of Electron Spectroscopy and Related Phenomena 190 (październik 2013): 137–43. http://dx.doi.org/10.1016/j.elspec.2013.06.007.

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Asano, Sho, Junichi Hata, Kenta Watanabe, Naoki Matsui, Kota Suzuki, Ryoji Kanno i Masaaki Hirayama. "Mechanical and Electrochemical Properties of Highly-Dense Li-Si Alloy Anodes Fabricated by Arc Plasma Deposition". ECS Meeting Abstracts MA2023-02, nr 2 (22.12.2023): 217. http://dx.doi.org/10.1149/ma2023-022217mtgabs.

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Silicon is one of the most promising anode materials because it has a very high theoretical capacity (4200 mAh g− 1). This capacity is about 10 times higher than that of carbon anode (372 mAh g− 1).[1] However, enormous volumetric change and mechanical stress occur in a silicon anode during electrochemical lithiation-delithiation. Consequently, the specific capacity is degraded during repetition of charge-discharge because of cutting off conductive paths caused by mechanical fracture. It is reported that pre-lithiation by sputtering and electrochemical methods suppresses fracture of silicon anodes by decrease in elastic modulus and yielding stress.[2] However, the reported Li-Si alloy anodes possesses the mechanical properties derived from both the deposited silicon and the voids generated during the synthetic processes. Therefore, a highly-dense alloy is necessary to investigate relationships between mechanical and electrochemical properties of Li-Si itself. We have already fabricated highly-dense amorphous silicon films by an arc plasma deposition (APD) method.[3] Thus, we attempted to fabricate highly-dense Li-Si alloy films by an APD method. The obtained Li-Si alloy films were investigated with focusing on relationships between mechanical properties and electrochemical properties. Li x Si (x = 0-3.56) alloy films were prepared on Al2O3(0001) single-crystal and Cu substrates by an APD method. Metallic lithium and B-doped silicon coated with carbon were used as target materials in the APD apparatus. The physical structures and chemical states of the obtained Li x Si alloy films were investigated with Raman spectroscopy, hard X-ray photoelectron spectroscopy (HAXPES), and neutron reflectometry (NR). Elastic modulus and hardness of the Li x Si alloy films were calculated from load-displacement curves gained by nanoindentation measurement. Constant-current charge-discharge tests were carried out with 2032-type coin cells assembled using the Li x Si films as the working electrodes, Li foils as counter electrodes, and 1 M LiPF6 in EC: DEC 3:7 vol% as electrolytes. The charge-discharge tests were conducted with constant current of 0.01-0.16 mA (1C rate), lower and upper voltages of 20 mV and 1.5 V vs. Li/Li+. In HAXPES spectra, Si 2p peaks derived from Si0 shifted to lower binding energy compared to the Si (x = 0) film as x increased. Therefore, Li x Si alloy films with different compositions were successfully fabricated by the APD method. The peaks because of Si-Si bonds in Raman spectra also shifted to lower wavenumber with the increase in x. The shifts suggest that the length of the Si-Si bonds extended with the increase in x. The NR analyses revealed that Li x Si alloy films possessed the smooth surface with the roughness less than 3 nm. The elastic modulus and hardness of Li x Si alloy films decreased as x increased, meaning that Li x Si alloy films were softer and more easily deformed compared to Si films. In addition, the elastic modulus and hardness of Li x Si alloy films were higher than those of Li x Si films previously reported,[2] suggesting that the APD method more densely made the Li x Si alloy films than the reported sputtering and electrochemical methods. Thus, the objective highly-dense films of Li x Si alloys were successfully obtained. The plateaus corresponding to the reactions of Li x Si ↔︎ Li x ’Si ↔︎ Li y Si (x < x’ < y) were observed in charge-discharge curves of Li x Si alloy films. The first discharge capacities of Li x Si alloy films were lower than the theoretical capacity of silicon. This is due to the existence of lithium in the structure by pre-lithiation. Cycle stabilities of Li x Si alloy films were superior to the Si film. To reveal factors of the cycle stabilizing, the charge-discharge reactions were analyzed with dQ/dV plots. The peaks around 0.5 V in the delithation process decreased about Si film. This decrease in the reaction peak is attributed to the decrease in the active species during the reaction process because of the fracture. In contrast, the peaks of Li x Si alloy films around 0.5 V hardly decreased. This result suggests that delamination and fracture by volumetric change during charge-discharge processes were suppressed in Li x Si alloy films because of their softness. Thus, the analyses of the highly-dense Li x Si alloy films fabricated by the APD method clarified that cycle stabilities of active materials were improved by controlling mechanical properties. [1] Ashuri, M.et al., Nanoscale 2016, 8, (1), 74-103. [2] Sitinamaluwa, H. et al., RSC Adv. 2017, 7, 13487-13497. [3] Asano, S. et al., Highly-dense and smooth amorphous silicon films fabricated by arc plasma deposition and electrochemical properties., ACSSI-17, 3A-06, 9.15.2022.

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Kuroda, Masato, Morihiko Okuno, Daisuke Okuda i Masashi Ishikawa. "Improvement of Sulfur Cathode Reversibility by Specific Chemical Lithium Pre-doping Method". ECS Meeting Abstracts MA2022-02, nr 64 (9.10.2022): 2312. http://dx.doi.org/10.1149/ma2022-02642312mtgabs.

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1.Intoroduction Recently, lithium-ion batteries (LIBs) have been required in terms of a high energy density for large-scale applications such as power supplies for electric vehicles. Lithium-sulfur (Li-S) batteries are, therefore, expected as next generation batteries because of their high energy density. Sulfur is utilized as cathode material for Li-S batteries because of a high specific capacity. However, sulfur has a low electric conductivity and a risk of dissolution into an electrolyte during a charge-discharge process [1]. L. Nazar et al. applied activated carbon as substrate for sulfur to help electric conduction and prevent dissolution of sulfur [2]. The activated carbon allows Li-S batteries to show high specific capacity with high reversibility. Even if these problems are solved, however, Li-S batteries have a further problem of excessive initial irreversible capacity during the first discharge process. Li pre-doping is a useful technique to cancel the large irreversible capacity in actual LIBs. Abe et al. reported a chemical lithium pre-doping method for a graphite using lithium naphthalenide [3]. Studies have been reported on the use of such pre-doping to improve the performance of Li-S batteries, for instance, with a sulfur-Ketjenblack composite cathode [4]. In our previous study, we have applied that method to a sulfur cathode composed of microporous activated carbon and sulfur before cell assembly and developed a Li2S cathode that suppressed the initial irreversible capacity during the first discharge process. However, the Li2S cathode showed an unignorable initial irreversible capacity and poor cycle life [5]. This work attempts to improve the reversible capacity of the Li2S cathode by a specialized chemical lithium pre-doping method. Our report would lead to the proposal of novel cathode and anode options in Li-S batteries. Method 2-1. Fabrication of lithium naphthalenide solution As Li metal and Li2S are both sensitive to moisture in air, all the following synthesis processes were carried out in an Ar-filled glove box. Lithium naphthalenide, a dark green solution was prepared by mixing an equal mol amount of Li metal with naphthalene in a cyclic ether solvent. 2-2. Fabrication of Li2S-AC cathodes Each sulfur cathode was prepared by mixing the S-AC (a composite of microporous activated carbon and sulfur), acetylene black, carboxymethyl cellulose, and styrene butadiene rubber at a respective weight ratio of 93: 3: 2: 2 and coating the resulting aqueous slurry on a carbon paper. The 1M lithium naphthalenide solution was dropped on the sulfur cathode. After 20 min reaction, the cathode was rinsed several times with 2–dimethoxyethane (DME) to remove the residues of reagents. The cathode was then dried under reduced pressure for 12 h. After that, the resulting Li2S cathode was impregnated with a mixture of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) (VC: FEC = 1: 1 by weight). After 20 min impregnation, the cathode was dried under reduced pressure for 12 h. 2-3. Assembling of cells Cells were assembled with the Li2S electrode and Li metal foil as an anode. Lithium bis(trifluorosulfonyl)imide (LiTFSI): tetraglyme (G4): 1,1,2,2–tetrafluoroethyl–2,2,3,3–tetrafluoropropyl ether (D2) at a respective ratio of 10: 8: 40 (by mol) was used as the electrolyte. 3.Major results and discussion The Li2S cathode without the VC/FEC impregnation showed an initial charge capacity of 1791 mAh g-1 and an initial discharge capacity of 1298 mAh g-1, indicating a large irreversible capacity. In contrast, the Li2S cathode with the VC/FEC impregnation showed 1446 mAh g-1 and 1422 mAh g-1, respectively. Thus, the impregnation with VC/FEC reduced the initial irreversible capacity and improved the initial charge capacity. According to these results, Li remaining in the sulfur cathode would be partially consumed to form a film by the impregnation with VC/FEC. In addition, the capacity retention of the Li2S cathode with and without the VC/FEC impregnation was 73 % and 64 % at the 30th cycle, respectively. This suggests that the Li2S cathode with the film leads to better cycle performance than that without the film. We will also report the results of surface composition analysis of the Li2S cathode with and without the VC/FEC impregnation by Hard X-ray Photoelectron Spectroscopy (HAXPES). References [1] M. Wild et al., Energy & Environ. Sci., 8 (2015) 3477. [2] X. Ji et al., Nat. Mater., 8 (2009) 500. [3] T. Abe et al., J. Power Sources, 68 (1997) 216. [4] Y. Wu et al., J. Power Sources, 366 (2017) 65. [5] M. Okuno et al., The 60th Battery Symposium in Japan (2019) Abstract [3D01].

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Artyushkova, Kateryna, Stuart R. Leadley i Alexander G. Shard. "Introduction to reproducible laboratory hard x-ray photoelectron spectroscopy". Journal of Vacuum Science & Technology A 42, nr 5 (15.07.2024). http://dx.doi.org/10.1116/6.0003740.

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X-ray sources with a photon energy higher than 2140 eV are increasingly being used for routine x-ray photoelectron spectroscopy (XPS) on laboratory-based instruments. This analytical approach is termed “HAXPES” (hard x-ray photoelectron spectroscopy). This article provides an overview of the current and potential future uses of laboratory-based HAXPES in comparison to routine XPS performed using Al Kα and Mg Kα x-ray sources. The standardization of XPS has occurred over 30 years and many of the procedures and reference works are specific to the use of Al Kα and Mg Kα x-ray sources. In this article, we discuss the translation of standard XPS practices to HAXPES, indicate useful resources for HAXPES users, and highlight areas where there is a need for improved information and guidance.

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