Local structure around In atoms in coherently grownm-plane InGaN film

The local structure around In atoms in anm-plane In0.06Ga0.94N film coherently grown on a freestandingm-plane GaN substrate was investigated by polarization-dependent X-ray absorption fine-structure. A step-by-step fitting procedure was proposed for them-plane wurtzite structure. The interatomic distance for the first nearest neighbour In—N atomic pairs was almost isotropic. For the second nearest In—Ga pairs, the interatomic distances along them- anda-axes were longer and shorter, respectively, than that in strain-free virtual crystals as expected for them-plane compressive strain. In contrast, the In—Ga interatomic distance in thec-direction was elongated in spite of the compressive strain, which was explained in terms of the anisotropic atomic structure on them-plane. The local strain in them-plane film was more relaxed than that in coherently grownc-plane single quantum wells. A few In atoms were atomically localized in all directions, and thus localized excitonic emission is expected as in the case ofc-plane InGaN.

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Luminescence And Structural Properties Of InGaN Epilayer, Quantum Well And Quantum Dot Samples Using Synchrotron Excitation

MRS Proceedings ◽

10.1557/proc-639-g9.11 ◽

2000 ◽

Vol 639 ◽

Author(s):

K.P. O'Donnell ◽

R.W. Martin ◽

M.E. White ◽

M.J. Tobin ◽

J.F.W. Mosselmans ◽

...

Keyword(s):

Quantum Wells ◽

Local Structure ◽

Luminescence Decay ◽

X Rays ◽

X Ray ◽

Scanning Confocal Microscopy ◽

Photoluminescence Decay ◽

Large Pulse ◽

X Ray Absorption ◽

Ingan Quantum Wells

ABSTRACTThe Daresbury synchrotron radiation source (SRS) provides bright, tunable x-rays for scattering and absorption probes of local structure. Scanning confocal microscopy and luminescence decay measurements employ the SRS in alternative ways, as a tunable luminescence excitation engine and as a source of weak, 160 ps pulses with a large pulse-topulse separation, respectively. This report first describes local atomic structure studies of InGaN epilayers by extended x-ray absorption fine structure (EXAFS). In addition, we report photoluminescence (PL) imaging, PL microspectroscopy and photoluminescence decay studies of various nitride samples, including tailored InGaN quantum wells and discs.

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TheMXANprocedure: a new method for analysing the XANES spectra of metalloproteins to obtain structural quantitative information

Journal of Synchrotron Radiation ◽

10.1107/s0909049502018137 ◽

2002 ◽

Vol 10 (1) ◽

pp. 51-57 ◽

Cited By ~ 124

Author(s):

M. Benfatto ◽

S. Della Longa ◽

C. R. Natoli

Keyword(s):

Local Structure ◽

Experimental Spectrum ◽

Quantitative Information ◽

Geometrical Parameters ◽

Absorption Data ◽

Edge Structure ◽

X Ray ◽

Fitting Procedure ◽

Starting Conditions ◽

X Ray Absorption

The first quantitative analyses are reported of the FeK-edge polarized X-ray absorption near-edge structure (XANES) of a single crystal of the iron protein carbonmonoxy-myoglobin (MbCO) and of its cryogenic photoproduct Mb*CO. The CO—Fe–heme local structure has been determined using a novel fitting procedure, namedMXAN, which is able to fit the XANES part (from the edge to about 200 eV) of experimental X-ray absorption data. This method is based on the comparison between the experimental spectrum and several theoretical spectra that are generated by changing the relevant geometrical parameters of the site around the absorbing atom. The theoretical spectra are derived in the framework of the full multiple-scattering approach. TheMXANprocedure is able to recover information about the symmetry and atomic distances, and the solution is found to be independent of the starting conditions. The extracted local structure of Mb*CO includes an Fe—CO distance of 3.08 (7) Å, with a tilting angle between the heme normal and the Fe—C vector of 37 (7)° and a bending angle between the Fe—C vector and the C—O bond of 31 (5)°

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Application of In Situ X-ray Absorption Spectroscopy to Study Dilute Chromium Ions in a Molten Chloride Salt

10.26434/chemrxiv.9959807 ◽

2019 ◽

Author(s):

Jisue Moon ◽

Carter Abney ◽

Dmitriy Dolzhnikov ◽

James M. Kurley ◽

Kevin A. Beyer ◽

...

Keyword(s):

Absorption Spectroscopy ◽

Local Structure ◽

Chloride Salt ◽

X Ray ◽

Molten Chloride ◽

Stable Species ◽

Higher Temperature ◽

Cr Concentration ◽

X Ray Absorption

The local structure of dilute CrCl3 in a molten MgCl2:KCl salt was investigated by in situ x-ray absorption spectroscopy (XAS) at temperatures from room temperature to 800oC. This constitutes the first experiment where dilute Cr speciation is explored in a molten chloride salt, ostensibly due to the compounding challenges arising from a low Cr concentration in a matrix of heavy absorbers at extreme temperatures. CrCl3 was confirmed to be the stable species between 200 and 500oC, while mobility of metal ions at higher temperature (>700oC) prevented confirmation of the local structure.

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Local structure and cation distribution analysis of Mn1-xZnxFe2O4 powders by X-ray Absorption Near Edge Structure Spectroscopy

Radiation Physics and Chemistry ◽

10.1016/j.radphyschem.2021.109628 ◽

2021 ◽

pp. 109628

Author(s):

Jaru Jutimoosik ◽

Pinit Kidkhunthod ◽

Theerachai Bongkarn ◽

Rattikorn Yimnirun

Keyword(s):

Cation Distribution ◽

Local Structure ◽

Distribution Analysis ◽

Edge Structure ◽

X Ray ◽

X Ray Absorption

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Local Structure and Dynamics of Functional Materials Studied by X-ray Absorption Fine Structure

Symmetry ◽

10.3390/sym13081315 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1315

Author(s):

Takafumi Miyanaga

Keyword(s):

Fine Structure ◽

Local Structure ◽

Chemical Reactivity ◽

Functional Materials ◽

X Ray ◽

Structure And Dynamics ◽

Absorption Fine ◽

Structure Phase Transition ◽

Local Electronic Structure ◽

X Ray Absorption

X-ray absorption fine structure (XAFS) is a powerful technique used to analyze a local electronic structure, local atomic structure, and structural dynamics. In this review, I present examples of XAFS that apply to the local structure and dynamics of functional materials: (1) structure phase transition in perovskite PbTiO3 and magnetic FeRhPd alloys; (2) nano-scaled fluctuations related to their magnetic properties in Ni–Mn alloys and Fe/Cr thin films; and (3) the Debye–Waller factors related to the chemical reactivity for catalysis in polyanions and ligand exchange reaction. This study shows that the local structure and dynamics are related to the characteristic function of the materials.

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The Study of Magnetic Properties for Non-Magnetic Ions Doped BiFeO3

Materials ◽

10.3390/ma14154061 ◽

2021 ◽

Vol 14 (15) ◽

pp. 4061

Author(s):

Yongtao Li ◽

Liqing Liu ◽

Dehao Wang ◽

Hongguang Zhang ◽

Xuemin He ◽

...

Keyword(s):

Magnetic Properties ◽

Local Structure ◽

Metal Ion ◽

Single Phase ◽

Sol Gel ◽

X Ray ◽

Co Doping ◽

Magnetic Ions ◽

X Ray Absorption ◽

Fe Ions

BiFeO3 is considered as a single phase multiferroic. However, its magnetism is very weak. We study the magnetic properties of BiFeO3 by Cu and (Cu, Zn). Polycrystalline samples Bi(Fe0.95Cu0.05)O3 and BiFe0.95(Zn0.025Cu0.025)O3 are prepared by the sol-gel method. The magnetic properties of BiFe0.95(Zn0.025Cu0.025)O3 are greater than that of BiFeO3 and Bi(Fe0.95Cu0.05)O3. The analyses of X-ray absorption fine structure data show that the doped Cu atoms well occupy the sites of the Fe atoms. X-ray absorption near edge spectra data confirm that the valence state of Fe ions does not change. Cu and Zn metal ion co-doping has no impact on the local structure of the Fe and Bi atoms. The modification of magnetism by doping Zn can be understood by the view of the occupation site of non-magnetically active Zn2+.

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Local atomic structure in tetragonal pure ZrO2nanopowders

Journal of Applied Crystallography ◽

10.1107/s0021889809054983 ◽

2010 ◽

Vol 43 (2) ◽

pp. 227-236 ◽

Cited By ~ 16

Author(s):

Leandro M. Acuña ◽

Diego G. Lamas ◽

Rodolfo O. Fuentes ◽

Ismael O. Fábregas ◽

Márcia C. A. Fantini ◽

...

Keyword(s):

Tetragonal Phase ◽

Local Structure ◽

X Ray Diffraction ◽

X Ray ◽

Atomic Structures ◽

Crystallite Sizes ◽

Exafs Study ◽

The Difference ◽

X Ray Absorption ◽

Good Agreement

The local atomic structures around the Zr atom of pure (undoped) ZrO2nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO2nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr—O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye–Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to thezdirection; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

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