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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Attosecond Soft X-Ray Absorption Spectroscopy in Graphite
摘要： X-ray absorption fine-structure (XAFS) spectroscopy is a well-established technique capable to extract information on the electronic and lattice structure of a material with atomic resolution. Analysis of the XAFS spectrum in the near-edge region (XANES) provides information about the electronic configuration. Structural information is extracted from the extended XAFS (EXAFS) spectrum, consisting of several hundreds of eV above the absorption edge. Connecting the spectroscopic capabilities of XAFS technique to high temporal resolution would give the possibility to follow electronic and lattice dynamics in real time. Here, we present the simultaneously access to electronic and lattice parameters via XAFS spectroscopy using isolated attosecond soft X-ray (SXR) pulses covering the entire water window region (280 eV to 540 eV). We demonstrate the novel capabilities of attosecond XAFS (attoXAFS) by identifying the (cid:1)* and (cid:1)* orbital contributions to the density of states in highly oriented pyrolithic graphite (HOPG) simultaneously with the four characteristic bonding distances of graphite’s hexagonal lattice.
关键词： attosecond,graphite,soft X-ray,electronic and lattice dynamics,XAFS spectroscopy
更新于2025-09-11 14:15:04
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Ion irradiation effects on Sb-rich GaSb films
摘要： Here we show the formation of amorphous, non-stoichiometric GaSb films by magnetron sputtering and the ion irradiation effects on the films. GaSb films in the 20–300 nm thickness range were deposited by magnetron sputtering on SiO2/Si substrates at room temperature and subsequently irradiated with 17 MeV Au+7 ions at different fluences. Structural, compositional, and morphological characterizations were performed by means of x-ray diffraction, Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, scanning electron microscopy and x-ray absorption fine structure analyses. We could verify that, throughout the above-mentioned thickness range, films were amorphous, with excess Sb to the ratio 1:2 (Ga:Sb). The initially compact films attained a foam-like structure after irradiation, with significant swelling that is dependent on the initial film thickness: the thicker the film, the more it swelled. The excess Sb attained different oxidation states depending on film thickness and this influenced the final density of the films, thus influencing the swelling. The local atomic structure around Ga atoms was also investigated, revealing a decrease in Ga–Sb scattering contribution with increasing irradiation fluence, at the same time as the increase in Ga–O scattering for irradiation fluence above 1×1014 at/cm2 (inclusive).
关键词： XPS,XAFS,RBS,GaSb films,ion irradiation,XRD,magnetron sputtering
更新于2025-09-09 09:28:46
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Local insight into the La-induced structural phase transition in multiferroic BiFeO3 ceramics by X-ray absorption fine structure spectroscopy
摘要： Substitution of bismuth by rare-earth (RE) ions is of great technological importance to develop room-temperature BiFeO3-based multiferroic materials. Despite this interest, many fundamental properties and the structure-property correlations of RE-doped BiFeO3 remain poorly understood. Here we report a systematical experimental and theoretical exploration on the structural phase transition in Bi1-xLaxFeO3 (0 ≤ x ≤ 0.2) ceramics. By using x-ray absorption fine structure spectroscopy, we for the first time show that the La3+ dopants in fact substitute the Bi site of a secondary nanosized particles with orthorhombic Pbam symmetry instead of the long-believed parental rhombohedral R3c phase at all La3+ doping concentrations (0.001 ≤ x ≤ 0.2). This finding is further supported by complementary studies of transmission electron microscopy and thermodynamic preference, and it casts serious challenges on the prevailing assumption of La substitution on the Bi3+ site in R3c structure when x ≤ 0.1 as well as the previously proposed origin of enhanced functional properties based on morphotropic phase boundary. This new insight may ignite a revival on exploring the underlying multiferroic mechanisms in BiFeO3-based materials and facilitate the bottom-up design of novel multifunctional devices.
关键词： XAFS,BiFeO3,structural phase transition,La doping,multiferroic materials
更新于2025-09-04 15:30:14
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IR and XAFS studies of photoluminescent Ag-type zeolite-A
摘要： We examined the relation between the zeolite framework, Ag clusters, and properties of photoluminescence (PL) using in-situ infrared spectroscopy (IR) and X-ray absorption fine structure (XAFS). The Ag clusters are generated in the cavity of Ag-type zeolite-A that is cooled to room temperature after heating at 500°C for 24 hour under vacuum or in atmosphere. The Ag clusters in the zeolite cavity break down when air is introduced. According to the formation and breakdown of the Ag cluster, the infrared spectrum of the zeolite framework changed slightly. Then, this change was compensated by irradiation of the excitation light. Results suggest that the structural change in the zeolite induced by the formation and breakdown of the Ag clusters is a key point of the PL mechanism.
关键词： infrared spectroscopy,XAFS,Ag clusters,photoluminescence,Ag-type zeolite-A
更新于2025-09-04 15:30:14