50 results on '"Y. C. Shao"'
Search Results
2. Time-resolved RIXS experiment with pulse-by-pulse parallel readout data collection using X-ray free electron laser
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H. Lu, A. Gauthier, M. Hepting, A. S. Tremsin, A. H. Reid, P. S. Kirchmann, Z. X. Shen, T. P. Devereaux, Y. C. Shao, X. Feng, G. Coslovich, Z. Hussain, G. L. Dakovski, Y. D. Chuang, and W. S. Lee
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Medicine ,Science - Abstract
Abstract Time-resolved resonant inelastic X-ray scattering (RIXS) is one of the developing techniques enabled by the advent of X-ray free electron laser (FEL). It is important to evaluate how the FEL jitter, which is inherent in the self-amplified spontaneous emission process, influences the RIXS measurement. Here, we use a microchannel plate (MCP) based Timepix soft X-ray detector to conduct a time-resolved RIXS measurement at the Ti L 3-edge on a charge-density-wave material TiSe2. The fast parallel Timepix readout and single photon sensitivity enable pulse-by-pulse data acquisition and analysis. Due to the FEL jitter, low detection efficiency of spectrometer, and low quantum yield of RIXS process, we find that less than 2% of the X-ray FEL pulses produce signals, preventing acquiring sufficient data statistics while maintaining temporal and energy resolution in this measurement. These limitations can be mitigated by using future X-ray FELs with high repetition rates, approaching MHz such as the European XFEL in Germany and LCLS-II in the USA, as well as by utilizing advanced detectors, such as the prototype used in this study.
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- 2020
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3. Anisotropy in the magnetic interaction and lattice-orbital coupling of single crystal Ni3TeO6
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Anirudha Ghosh, K.-H. Chen, X.-S. Qiu, S. H. Hsieh, Y. C. Shao, C. H. Du, H. T. Wang, Y. Y. Chin, J. W. Chiou, Sekhar C. Ray, H. M. Tsai, C. W. Pao, H. J. Lin, J. F. Lee, Raman Sankar, F. C. Chou, and W. F. Pong
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Orbit-lattice Coupling ,X-ray Magnetic Circular Dichroism (XMCD) ,XMCD Spectra ,NiO6 Octahedra ,Spin Axis Parallel ,Medicine ,Science - Abstract
Abstract This investigation reports on anisotropy in the magnetic interaction, lattice-orbital coupling and degree of phonon softening in single crystal Ni3TeO6 (NTO) using temperature- and polarization-dependent X-ray absorption spectroscopic techniques. The magnetic field-cooled and zero-field-cooled measurements and temperature-dependent Ni L 3,2-edge X-ray magnetic circular dichroism spectra of NTO reveal a weak Ni-Ni ferromagnetic interaction close to ~60 K (T SO: temperature of the onset of spin ordering) with a net alignment of Ni spins (the uncompensated components of the Ni moments) along the crystallographic c-axis, which is absent from the ab-plane. Below the Néel temperature, T N~ 52 K, NTO is stable in the antiferromagnetic state with its spin axis parallel to the c-axis. The Ni L 3,2-edge X-ray linear dichroism results indicate that above T SO, the Ni 3d e g electrons preferentially occupy the out-of-plane 3d 3z 2 −r 2 orbitals and switch to the in-plane 3d x 2 −y 2 orbitals below T SO. The inherent distortion of the NiO6 octahedra and anisotropic nearest-neighbor Ni-O bond lengths between the c-axis and the ab-plane of NTO, followed by anomalous Debye-Waller factors and orbital-lattice in conjunction with spin-phonon couplings, stabilize the occupied out-of-plane (3d 3z 2 −r 2) and in-plane (3d x 2 −y 2) Ni e g orbitals above and below T SO, respectively.
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- 2018
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4. Anisotropy in the thermal hysteresis of resistivity and charge density wave nature of single crystal SrFeO3-δ: X-ray absorption and photoemission studies
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S. H. Hsieh, R. S. Solanki, Y. F. Wang, Y. C. Shao, S. H. Lee, C. H. Yao, C. H. Du, H. T. Wang, J. W. Chiou, Y. Y. Chin, H. M. Tsai, J.-L. Chen, C. W. Pao, C.-M. Cheng, W.-C. Chen, H. J. Lin, J. F. Lee, F. C. Chou, and W. F. Pong
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Medicine ,Science - Abstract
Abstract The local electronic and atomic structures of the high-quality single crystal of SrFeO3-δ (δ~0.19) were studied using temperature-dependent x-ray absorption and valence-band photoemission spectroscopy (VB-PES) to investigate the origin of anisotropic resistivity in the ab-plane and along the c-axis close to the region of thermal hysteresis (near temperature for susceptibility maximum, Tm~78 K). All experiments herein were conducted during warming and cooling processes. The Fe L 3,2-edge X-ray linear dichroism results show that during cooling from room temperature to below the transition temperature, the unoccupied Fe 3d e g states remain in persistently out-of-plane 3d 3z 2 -r 2 orbitals. In contrast, in the warming process below the transition temperature, they change from 3d 3z 2 -r 2 to in-plane 3d x 2 -y 2 orbitals. The nearest-neighbor (NN) Fe-O bond lengths also exhibit anisotropic behavior in the ab-plane and along the c-axis below Tm. The anisotropic NN Fe-O bond lengths and Debye-Waller factors stabilize the in-plane Fe 3d x 2 -y 2 and out-of-plane 3d 3z 2 -r 2 orbitals during warming and cooling, respectively. Additionally, a VB-PES study further confirms that a relative band gap opens at low temperature in both the ab-plane and along the c-axis, providing the clear evidence of the charge-density-wave nature of SrFeO3-δ (δ~0.19) single crystal.
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- 2017
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5. Impact of chemotherapy on surgical outcomes in ileostomy reversal: a propensity score matching study from a single centre
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H.-H. Cheng, Y.-C. Shao, C.-Y. Lin, T.-W. Chiang, M.-C. Chen, T.-Y. Chiu, Y.-L. Huang, C.-C. Chen, C.-P. Chen, and F.-F. Chiang
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Gastroenterology ,Surgery - Published
- 2023
6. The effect of orbital-lattice coupling on the electrical resistivity of YBaCuFeO5 investigated by X-ray absorption
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X.-S. Qiu, Y. H. Liang, C. W. Pao, S. H. Hsieh, W. F. Pong, Huanchun Wang, J. F. Lee, M. K. Srivastava, C.-H. Lai, H. J. Lin, Chao-Hung Du, K. Asokan, Y. C. Shao, Y. C. Lai, H. M. Tsai, Yi-Ying Chin, and J. W. Chiou
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Multidisciplinary ,Valence (chemistry) ,Materials science ,Extended X-ray absorption fine structure ,lcsh:R ,lcsh:Medicine ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,Article ,Bond length ,Crystallography ,Electrical resistivity and conductivity ,Lattice (order) ,0103 physical sciences ,Antiferromagnetism ,lcsh:Q ,010306 general physics ,0210 nano-technology ,Condensed-matter physics ,lcsh:Science ,Single crystal - Abstract
Temperature-dependent X-ray absorption near-edge structures, X-ray linear dichroism (XLD) and extended X-ray absorption fine structure (EXAFS) spectroscopic techniques were used to investigate the valence state, preferred orbital and local atomic structure that significantly affect the electrical and magnetic properties of a single crystal of YBaCuFeO5 (YBCFO). An onset of increase of resistivity at ~180 K, followed by a rapid increase at/below 125 K, is observed. An antiferromagnetic (AFM)-like transition is close to the temperature at which the resistivity starts to increase in the ab-plane and is also observed with strong anisotropy between the ab-plane and the c-axis. The XLD spectra at the Fe L3,2-edge revealed a change in Fe 3d eg holes from the preferential $${\bf{3}}{{\boldsymbol{d}}}_{{{\bf{x}}}^{{\bf{2}}}{\boldsymbol{-}}{{\bf{y}}}^{{\bf{2}}}}$$3dx2−y2 orbital at high temperature (300–150 K) to the $${\bf{3}}{{\boldsymbol{d}}}_{{{\bf{3}}{\bf{z}}}^{{\bf{2}}}{\boldsymbol{-}}{{\bf{r}}}^{{\bf{2}}}}$$3d3z2−r2 orbital at/below 125 K. The analysis of the Fe K-edge EXAFS data of YBCFO further revealed an unusual increase in the Debye-Waller factor of the nearest-neighbor Fe-O bond length at/below 125 K, suggesting phonon-softening behavior, resulting in the breaking of lattice symmetry, particularly in the ab-plane of Fe-related square pyramids. These findings demonstrate a close correlation between electrical resistivity and coupling of the preferred Fe 3d orbital with lattice distortion of a single crystal of YBCFO.
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- 2019
7. Enhanced orbital anisotropy through the proximity to a SrTiO3 layer in the perovskite iridate superlattices
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Y. C. Shao, Yi-De Chuang, Dawei Shen, Xuefei Feng, J. M. Lee, Wanling Liu, Nian Zhang, Xiaosong Liu, Wencheng Huang, and Jiamin Fu
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Condensed Matter::Materials Science ,X-ray absorption spectroscopy ,Materials science ,Atomic orbital ,Absorption spectroscopy ,Condensed matter physics ,K-edge ,Orbital hybridisation ,Superlattice ,Anisotropy ,Perovskite (structure) - Abstract
We have used angle-dependent soft x-ray absorption spectroscopy (XAS) at the O K edge and first-principles calculations to investigate the electronic structures of iridate-based superlattices (SrIrO3)m/(SrTiO3) (m=1, 2, 3, and ∞). We focus on the pre-edge Ir 5d t2g-O 2p orbital hybridization feature in the XAS spectra. By varying the measurement geometry relative to the incident photon polarization, we are able to extract the dichroic contrast and observe the systematic increase in the anisotropy of Ir 5d orbitals as m decreases. First-principles calculations elucidate the orbital anisotropy coming mainly from the enhanced out-of-plane compression of IrO6 octahedra in the SrIrO3 layers that are adjacent to the inserted SrTiO3 layers. As m decreases, the increased volume fraction of these interfacial SrIrO3 layers and their contact with the SrTiO3 layers within the (SrIrO3)m/(SrTiO3) supercell lead to enhanced orbital anisotropy. Furthermore, the tilt and rotation of IrO6 octahedra are shown to be essential to understand the subtle orbital anisotropy in these superlattices, and constraining these degrees of freedom will give an incorrect trend. Our results demonstrate that the structural constraint from the inserted SrTiO3 layers, in addition to other electronic means such as polar interface and charge transfer, can serve as a knob to control the orbital degree of freedom in these iridate-based superlattices.
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- 2021
8. Electronic structure of rhombohedral CrX3 (X=Br, Cl, I) van der Waals crystals
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Y.-D. Chuang, L. Craco, Y. C. Shao, S. S. Carara, and B. Freelon
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Generalized gradient ,Paramagnetism ,symbols.namesake ,Materials science ,Absorption spectroscopy ,Condensed matter physics ,symbols ,Quasiparticle ,Electronic structure ,Trigonal crystal system ,van der Waals force ,Electronic states - Abstract
Author(s): Craco, L; Carara, SS; Shao, YC; Chuang, YD; Freelon, B | Abstract: We perform a comprehensive analysis of both the chemical and correlated electronic structure reconstruction of rhombohedral CrX3 (X=Br, Cl, I) van der Waals bulk crystals. Using the generalized gradient approximation (GGA) plus dynamical mean-field theory we explicitly demonstrate the importance of local dynamical correlations for a consistent understanding of emergent Kondo quasiparticles and Mott localized electronic states, showing the interplay between material-dependent one-electron GGA line-shape and multiorbital electronic interactions. To probe the correlated paramagnetic electronic state we performed x-ray absorption spectroscopy measurements for CrCl3 and CrBr3 bulk crystals. Our correlated many-body study is relevant to understanding the electronic structure reconstruction of paramagnetic Cr-trihalide crystals and should be widely applicable to other van der Waals magnetic materials.
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- 2021
9. Evolution of superconductivity in K 2−x Fe 4+y Se 5 : Spectroscopic studies of X-ray absorption and emission
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Y. C. Shao, M.K. Wu, Jinghua Guo, S. H. Hsieh, Chih-Han Wang, C. L. Chen, C. W. Pao, H. T. Wang, Anirudha Ghosh, Yanlan Liu, J. F. Lee, Way-Faung Pong, Y. D. Chuang, and J. W. Chiou
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Superconductivity ,Resonant inelastic X-ray scattering ,Bond length ,X-ray absorption spectroscopy ,Magnetization ,Electron pair ,Multidisciplinary ,Materials science ,Condensed matter physics ,Vacancy defect ,Physical Sciences ,Spin magnetic moment - Abstract
Significance We report the study using X-ray absorption and resonant inelastic X-ray scattering techniques to investigate the evolution of superconductivity in K 1.9 Fe 4.2 Se 5 , which was synthesized from its nonsuperconducting parent compound, K 2 Fe 4 Se 5 , by increasing the Fe concentration. The results provide a deeper insight into the magnetic and local electronic properties of K 1.9 Fe 4.2 Se 5 , such as a decrease in antiferromagnetic spin magnetic moment of Fe, charge transfer, and hybridization between Fe 3 d –Se 4 p orbitals, and increase in the local static structural disorder, to gain an understanding of the evolution of superconductivity in the compound.
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- 2019
10. Fabrication and 3D Patterning of Bio‐Composite Consisting of Carboxymethylated Cellulose Nanofibers and Cobalt Ferrite Nanoparticles
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Pradosh Kumar Sahoo, Shashi B. Singh, Way-Faung Pong, S. H. Hsieh, Kuan-Hung Chen, Amit Khare, Mandar M. Shirolkar, D. S. Rana, Xian-Sheng Qiu, Y. C. Shao, and Mukta V. Limaye
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3d patterning ,Fabrication ,Materials science ,Composite number ,Cobalt ferrite nanoparticles ,General Chemistry ,law.invention ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,law ,Nanofiber ,Magnetic nanoparticles ,Cellulose ,Electron microscope - Published
- 2019
11. Strain effect on orbital and magnetic structures of Mn ions in epitaxial Nd0.35Sr0.65MnO3/SrTiO3 films using X-ray diffraction and absorption
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J. W. Chiou, Nishad G. Deshpande, H. M. Tsai, Way-Faung Pong, Jen-Jen Lin, K. Asokan, Yi Ying Chin, Y. C. Shao, S. H. Hsieh, H. J. Lin, H. T. Wang, Chao-Hung Du, Ping-Hung Yeh, and S. L. Cheng
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0301 basic medicine ,Multidisciplinary ,Materials science ,Magnetic circular dichroism ,Fermi level ,lcsh:R ,Analytical chemistry ,lcsh:Medicine ,Linear dichroism ,Article ,Pulsed laser deposition ,03 medical and health sciences ,symbols.namesake ,030104 developmental biology ,0302 clinical medicine ,Ferromagnetism ,X-ray crystallography ,symbols ,Antiferromagnetism ,lcsh:Q ,lcsh:Science ,Néel temperature ,030217 neurology & neurosurgery - Abstract
This study probes the temperature-dependent strain that is strongly correlated with the orbital and magnetic structures of epitaxial films of Nd0.35Sr0.65MnO3 (NSMO) that are fabricated by pulsed laser deposition with two thicknesses, 17 (NS17) and 103 nm (NS103) on SrTiO3 (STO) substrate. This investigation is probed using X-ray diffraction (XRD) and absorption-based techniques, X-ray linear dichroism (XLD) and the X-ray magnetic circular dichroism (XMCD). XRD indicates a significant shift in the (004) peak position that is associated with larger strain in NS17 relative to that of NS103 at both 30 and 300 K. Experimental and atomic multiplet simulated temperature-dependent Mn L3,2-edge XLD results reveal that the stronger strain in a thinner NS17 film causes less splitting of Mn 3d eg state at low temperature, indicating an enhancement of orbital fluctuations in the band above the Fermi level. This greater Mn 3d orbital fluctuation can be the cause of both the enhanced ferromagnetism (FM) as a result of spin moments and the reduced Néel temperature of C-type antiferromagnetism (AFM) in NS17, leading to the FM coupling of the canted-antiferromagnetism (FM-cAFM) state in NSMO/STO epitaxial films at low temperature (T = 30 K). These findings are also confirmed by Mn L3,2-edge XMCD measurements.
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- 2019
12. Momentum-resolved resonant inelastic soft X-ray scattering (qRIXS) endstation at the ALS
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Anton S. Tremsin, L. Andrew Wray, Jaemyung Kim, Brian M. Smith, John Pepper, Zahid Hussain, Jinghua Guo, Alex Frano, Y. C. Shao, Alejandro G. Cruz, Thomas P. Devereaux, Wei-Sheng Lee, Adrian Spucces, Adam Brown, Zhi-Xun Shen, Xuefei Feng, S. W. Huang, Kelly Hanzel, Yu Jen Chen, Robert Duarte, Wanli Yang, Yi-De Chuang, and Eric M. Gullikson
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Photon ,02 engineering and technology ,01 natural sciences ,law.invention ,Optics ,Highly oriented pyrolytic graphite ,law ,0103 physical sciences ,Physical and Theoretical Chemistry ,Spectroscopy ,Physics ,Radiation ,010304 chemical physics ,business.industry ,Scattering ,Free-electron laser ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Synchrotron ,Electronic, Optical and Magnetic Materials ,Resonant inelastic X-ray scattering ,K-edge ,0210 nano-technology ,business - Abstract
A momentum resolved resonant inelastic X-ray scattering (qRIXS) experimental station with continuously rotatable spectrometers and parallel detection is designed to operate at different beamlines at synchrotron and free electron laser (FEL) facilities. This endstation, currently located at the Advanced Light Source (ALS), has five emission ports on the experimental chamber for mounting the high-throughput modular soft X-ray spectrometers (MXS) [24]. Coupled to the rotation from the supporting hexapod, the scattered X-rays from 27.5° (forward scattering) to 152.5° (backward scattering) relative to the incident photon beam can be recorded, enabling the momentum-resolved RIXS spectroscopy. The components of this endstation are described in details, and the preliminary RIXS measurements on highly oriented pyrolytic graphite (HOPG) reveal the low energy vibronic excitations from the strong electron-phonon coupling at C K edge around σ* band. The grating upgrade option to enhance the performance at low photon energies is presented and the potential of this spectroscopy is discussed in summary.
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- 2022
13. Dynamic electron correlations with charge order wavelength along all directions in the copper oxide plane
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Andrea Damascelli, Bernhard Keimer, Yi-De Chuang, Ruidan Zhong, Martin Bluschke, Shimpei Ono, Ronny Sutarto, J. Schneeloch, Matteo Michiardi, G. D. Guo, Enrico Schierle, Matteo Minola, Yimeng Yang, Fabio Boschini, Xiaofeng Feng, Feizhou He, Y. C. Shao, Eugen Weschke, Alex Frano, E. H. da Silva Neto, and Soumita Das
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Electronic properties and materials ,Science ,FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,Electron ,01 natural sciences ,Article ,General Biochemistry, Genetics and Molecular Biology ,Superconducting properties and materials ,Superconductivity (cond-mat.supr-con) ,Condensed Matter - Strongly Correlated Electrons ,Condensed Matter::Superconductivity ,0103 physical sciences ,Coulomb ,Cuprate ,010306 general physics ,Translational symmetry ,Superconductivity ,Physics ,Multidisciplinary ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed matter physics ,Scattering ,Plane (geometry) ,Condensed Matter - Superconductivity ,Computer Science::Information Retrieval ,Charge (physics) ,General Chemistry ,021001 nanoscience & nanotechnology ,Coulomb interactions ,mechanical phases ,electrons ,scattering ,density ,superconductivity ,0210 nano-technology - Abstract
In strongly correlated systems the strength of Coulomb interactions between electrons, relative to their kinetic energy, plays a central role in determining their emergent quantum mechanical phases. We perform resonant x-ray scattering on Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, a prototypical cuprate superconductor, to probe electronic correlations within the CuO$_2$ plane. We discover a dynamic quasi-circular pattern in the $x$-$y$ scattering plane with a radius that matches the wave vector magnitude of the well-known static charge order. Along with doping- and temperature-dependent measurements, our experiments reveal a picture of charge order competing with superconductivity where short-range domains along $x$ and $y$ can dynamically rotate into any other in-plane direction. This quasi-circular spectrum, a hallmark of Brazovskii-type fluctuations, has immediate consequences to our understanding of rotational and translational symmetry breaking in the cuprates. We discuss how the combination of short- and long-range Coulomb interactions results in an effective non-monotonic potential that may determine the quasi-circular pattern., Comment: This is a post-peer-review, pre-copyedit version of an article published in Nature Communications. The final authenticated version is available online at: https://doi.org/10.1038/s41467-020-20824-7. Supplementary materials are available through the published version in Nature Communications
- Published
- 2021
14. Spectroscopic Determination of Key Energy Scales for the Base Hamiltonian of Chromium Trihalides
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Wenyu Huang, Gamini Sumanasekera, Xuefei Feng, B. Freelon, Yi-De Chuang, Jinghua Guo, Y. C. Shao, and Bhupendra Karki
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X-ray absorption spectroscopy ,Materials science ,Scattering ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Crystal ,symbols.namesake ,Chromium ,chemistry ,0103 physical sciences ,symbols ,General Materials Science ,Physical and Theoretical Chemistry ,van der Waals force ,010306 general physics ,0210 nano-technology ,Hamiltonian (quantum mechanics) ,Spectroscopy ,Multiplet - Abstract
The van der Waals (vdW) chromium trihalides (CrX3) exhibit field-tunable, two-dimensional magnetic orders that vary with the halogen species and the number of layers. Their magnetic ground states with proximity in energies are sensitive to the degree of ligand-metal (p-d) hybridization and relevant modulations in the Cr d-orbital interactions. We use soft X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS) spectroscopy at Cr L-edge along with the atomic multiplet simulations to determine the key energy scales such as the crystal field 10 Dq and interorbital Coulomb interactions under different ligand metal charge transfer (LMCT) in CrX3 (X= Cl, Br, and I). Through this systematic study, we show that our approach compared to the literature has yielded a set of more reliably determined parameters for establishing a base Hamiltonian for CrX3.
- Published
- 2021
15. Realization of electron antidoping by modulating the breathing distortion in BaBiO3
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Yi-De Chuang, Atsushi Fujimori, Qixin Liu, Aidi Zhao, Hua Zhou, Hongli Guo, Zhongping Wang, Xuefei Feng, Y. C. Shao, Qinwen Lu, Hui Cao, and Xiaofang Zhai
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Materials science ,Band gap ,Oxide ,FOS: Physical sciences ,breathing distortion ,Bioengineering ,Disproportionation ,02 engineering and technology ,Electron ,antidoping ,oxygen vacancies ,chemistry.chemical_compound ,band gap ,Distortion ,General Materials Science ,Nanoscience & Nanotechnology ,Condensed Matter - Materials Science ,Annihilation ,Condensed matter physics ,Mechanical Engineering ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,chemistry ,main group oxides ,0210 nano-technology ,Realization (systems) ,BaBiO3 ,Stoichiometry - Abstract
The recent proposal of antidoping scheme breaks new ground in conceiving conversely functional materials and devices, yet the few available examples belong to the correlated electron systems. Here we demonstrate both theoretically and experimentally that the main group oxide BaBiO3 is a model system for antidoping using oxygen vacancies. The first-principles calculations show that the band gap systematically increases due to the strongly enhanced Bi-O breathing distortions away from the vacancies and the annihilation of Bi 6s/O 2p hybridized conduction bands near the vacancies. The spectroscopic experiments confirm the band gap increasing systematically with electron doping, with a maximal gap enhancement of ~75% when the film’s stoichiometry is reduced to BaBiO2.75. The Raman and diffraction experiments show the suppression of the overall breathing distortion. The study unambiguously demonstrates the remarkable antidoping effect in a material without strong electron correlations and underscores the importance of bond disproportionation in realizing such an effect.
- Published
- 2020
16. Mott localization in the van der Waals crystal CrI3 : A GGA+DMFT study
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Y.-D. Chuang, L. Craco, Y. C. Shao, S. S. Carara, and B. Freelon
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Condensed Matter::Quantum Gases ,Physics ,X-ray absorption spectroscopy ,Absorption spectroscopy ,Electronic correlation ,Condensed matter physics ,Mott insulator ,02 engineering and technology ,Electronic structure ,021001 nanoscience & nanotechnology ,01 natural sciences ,Condensed Matter::Materials Science ,Paramagnetism ,symbols.namesake ,Ferromagnetism ,0103 physical sciences ,symbols ,Condensed Matter::Strongly Correlated Electrons ,van der Waals force ,010306 general physics ,0210 nano-technology - Abstract
Using the generalized gradient approximation plus dynamical mean-field theory ($\mathrm{GGA}+\mathrm{DMFT}$) we confirm the importance of multi-orbital dynamical correlations in determining the paramagnetic insulating state of $\mathrm{Cr}{\mathrm{I}}_{3}$. While the ferromagnetic phase reveals weak electronic correlation effects due to strong spin-orbital polarization, the Mott insulating state of paramagnetic $\mathrm{Cr}{\mathrm{I}}_{3}$ crystal is shown to be driven by the interplay between orbital-dependent one-electron lineshape and multi-orbital electronic interactions. To probe the paramagnetic Mott insulating state we performed x-ray absorption spectroscopy (XAS) measurements for the two structural phases of $\mathrm{Cr}{\mathrm{I}}_{3}$. Our study is relevant to understanding the orbital-selective electronic structure reconstruction of Mott insulators and should be applicable to other van der Waals bonded materials from bulk to the ultrathin limit.
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- 2020
17. Disparate Exciton-Phonon Couplings for Zone-Center and Boundary Phonons in Solid-State Graphite
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Anton S. Tremsin, Shawn Sallis, Xuefei Feng, Ruimin Qiao, Jinghua Guo, Li Cheng Kao, Zahid Hussain, Wanli Yang, Y. C. Shao, Yi-Sheng Liu, and Yi-De Chuang
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Physics ,Coupling constant ,Coupling ,Condensed Matter - Materials Science ,Condensed matter physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Phonon ,Scattering ,Exciton ,General Physics and Astronomy ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Applied Physics (physics.app-ph) ,Physics - Applied Physics ,Resonance (particle physics) ,Condensed Matter::Materials Science ,Condensed Matter - Strongly Correlated Electrons ,Highly oriented pyrolytic graphite ,Condensed Matter::Strongly Correlated Electrons ,Dimensionless quantity - Abstract
The exciton-phonon coupling in highly oriented pyrolytic graphite is studied using resonant inelastic X-ray scattering (RIXS) spectroscopy. With ~ 70 meV energy resolution, multiple low energy excitations associated with coupling to phonons can be clearly resolved in RIXS spectra. Using resonance dependence and the closed form for RIXS cross-section without considering the intermediate state mixing of phonon modes, the dimensionless coupling constant g is determined to be 5 and 0.4, corresponding to the coupling strength of 0.42 eV +/- 40 meV and 0.21 eV +/- 30 meV, for zone center and boundary phonons respectively. The reduced g value for zone-boundary phonon may be related to its double resonance nature., Main text is 20 pages with 4 figures Supplementary information is 10 pages with 3 figures
- Published
- 2020
18. Two-dimensional electron systems in perovskite oxide heterostructures: Role of the polarity-induced substitutional defects
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Aaron Bostwick, Cheng-Tai Kuo, Jean-Pascal Rueff, Shih-Chieh Lin, Slavomír Nemšák, Eli Rotenberg, Nicolas Gauquelin, Jaap Geessinck, Y. C. Shao, Charles S. Fadley, Yi-De Chuang, Yingying Peng, Arturas Vailionis, Mark Huijben, Eric M. Gullikson, I. L. Graff, G. Conti, Claus M. Schneider, Johan Verbeeck, Giacomo Claudio Ghiringhelli, Inorganic Materials Science, and MESA+ Institute
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Materials science ,Physics and Astronomy (miscellaneous) ,Magnetism ,Oxide ,FOS: Physical sciences ,02 engineering and technology ,Electron ,Conductivity ,Inelastic scattering ,01 natural sciences ,chemistry.chemical_compound ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,cond-mat.mes-hall ,General Materials Science ,010306 general physics ,Perovskite (structure) ,Condensed Matter - Materials Science ,Condensed matter physics ,Condensed Matter - Mesoscale and Nanoscale Physics ,Physics ,Materials Science (cond-mat.mtrl-sci) ,Heterojunction ,021001 nanoscience & nanotechnology ,cond-mat.mtrl-sci ,3. Good health ,chemistry ,Excited state ,0210 nano-technology - Abstract
The discovery of a two-dimensional electron system (2DES) at the interfaces of perovskite oxides such as LaAlO3 and SrTiO3 has motivated enormous efforts in engineering interfacial functionalities with this type of oxide heterostructures. However, its fundamental origins are still not understood, e.g. the microscopic mechanisms of coexisting interface conductivity and magnetism. Here we report a comprehensive spectroscopic investigation of the depth profile of 2DES-relevant Ti 3d interface carriers using depth- and element-specific techniques, standing-wave excited photoemission and resonant inelastic scattering. We found that one type of Ti 3d interface carriers, which give rise to the 2DES are located within 3 unit cells from the n-type interface in the SrTiO3 layer. Unexpectedly, another type of interface carriers, which are polarity-induced Ti-on-Al antisite defects, reside in the first 3 unit cells of the opposing LaAlO3 layer (~10 {\AA}). Our findings provide a microscopic picture of how the localized and mobile Ti 3d interface carriers distribute across the interface and suggest that the 2DES and 2D magnetism at the LaAlO3/SrTiO3 interface have disparate explanations as originating from different types of interface carriers., Comment: 28 pages, 4 figures; Supplemental Materials 19 pages
- Published
- 2020
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19. Anisotropy in the magnetic interaction and lattice-orbital coupling of single crystal Ni3TeO6
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F. C. Chou, C. W. Pao, Yi-Ying Chin, X.-S. Qiu, Chao-Hung Du, Huanchun Wang, Y. C. Shao, Hung-Ju Lin, Raman Sankar, Anirudha Ghosh, W. F. Pong, Sekhar C. Ray, S. H. Hsieh, Kuan-Hung Chen, H. M. Tsai, J. W. Chiou, and Jung-Sik Lee
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Materials science ,Science ,02 engineering and technology ,Linear dichroism ,01 natural sciences ,Spin Axis Parallel ,Article ,NiO6 Octahedra ,0103 physical sciences ,Antiferromagnetism ,010306 general physics ,Anisotropy ,XMCD Spectra ,Multidisciplinary ,Condensed matter physics ,Magnetic circular dichroism ,021001 nanoscience & nanotechnology ,X-ray Magnetic Circular Dichroism (XMCD) ,Bond length ,Ferromagnetism ,Orbit-lattice Coupling ,Medicine ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology ,Single crystal ,Néel temperature - Abstract
This investigation reports on anisotropy in the magnetic interaction, lattice-orbital coupling and degree of phonon softening in single crystal Ni3TeO6 (NTO) using temperature- and polarization-dependent X-ray absorption spectroscopic techniques. The magnetic field-cooled and zero-field-cooled measurements and temperature-dependent Ni L3,2-edge X-ray magnetic circular dichroism spectra of NTO reveal a weak Ni-Ni ferromagnetic interaction close to ~60 K (TSO: temperature of the onset of spin ordering) with a net alignment of Ni spins (the uncompensated components of the Ni moments) along the crystallographic c-axis, which is absent from the ab-plane. Below the Néel temperature, TN~ 52 K, NTO is stable in the antiferromagnetic state with its spin axis parallel to the c-axis. The Ni L3,2-edge X-ray linear dichroism results indicate that above TSO, the Ni 3d eg electrons preferentially occupy the out-of-plane 3d3z2−r2 orbitals and switch to the in-plane 3dx2−y2 orbitals below TSO. The inherent distortion of the NiO6 octahedra and anisotropic nearest-neighbor Ni-O bond lengths between the c-axis and the ab-plane of NTO, followed by anomalous Debye-Waller factors and orbital-lattice in conjunction with spin-phonon couplings, stabilize the occupied out-of-plane (3d3z2−r2) and in-plane (3dx2−y2) Ni eg orbitals above and below TSO, respectively.
- Published
- 2018
20. Electronic surface reconstruction of TiO2 nanocrystals revealed by resonant inelastic x-ray scattering
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Jin Zhang, Yoshihisa Harada, Sheraz Gul, Gongming Wang, Hideharu Niwa, Yat Li, Per-Anders Glans, Chieh-Ming Chen, Cheng-Hao Chuang, Jinghua Guo, Mukes Kapilashrami, Jin-Ming Chen, Way-Faung Pong, Ping-Hung Yeh, Jun Miyawaki, Chih-Ming Chang, and Y. C. Shao
- Subjects
Resonant inelastic X-ray scattering ,Materials science ,Electron diffraction ,Scattering ,Surfaces and Interfaces ,Electron ,Inelastic scattering ,Condensed Matter Physics ,Absorption (electromagnetic radiation) ,Molecular physics ,Excitation ,Surface reconstruction ,Surfaces, Coatings and Films - Abstract
The identification of lattice multiphases in TiO2 nanocrystals is studied by high resolution transmission electron microscope and electron diffraction patterns. Based on the spectroscopic analysis using soft x-ray absorption and resonant inelastic soft x-ray scattering, it is believed that the oxygen vacancies at the interface exhibit structural distortion of the TiO68− cluster around the defect site as for the multiphase lattice. We elucidate that the extra 3d electrons nearby induce the inelastic scattering features with the excitation energy dependence owing to different energy relaxation processes, a characteristic of the electron-phonon coupling or the nature of the electron-hole pair at the intermediate state. The manifold dd excitations driven by the strong interaction between Ti-3d and O-2p electrons are noticeably rich, coexisting on both Ti and O sites. This sophisticated experiment can advance the perspective of nanocomposite TiO2 for various interactions of surface Ti3+ in applications of future devices.
- Published
- 2021
21. The magnetic order in multiferroic DyMnO3
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Yi-De Chuang, Jin-Ming Chen, S. W. Huang, Robert W. Schoenlein, Jiunn-Yuan Lin, Ruimin Qiao, L. Andrew Wray, Horng-Tay Jeng, Wanli Yang, J. M. Lee, and Y. C. Shao
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Physics ,Diffraction ,Radiation ,010304 chemical physics ,Condensed matter physics ,Spins ,Scattering ,Exchange interaction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Ferroelectricity ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Atomic orbital ,0103 physical sciences ,Antiferromagnetism ,Multiferroics ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy - Abstract
With flexibility in tuning their electric and magnetic properties, multiferroics can be used in information exchange and storage in ways that are very different from the present electronic materials. Here we use resonant soft X-ray scattering spectroscopy to study the F -type ( 0 , τ , 0 ) and C -type (0, 1–2 τ , 0) diffraction peaks from sinusoidal antiferromagnetic spin order in multiferroic DyMnO 3 . By comparing the temperature dependence of ordering wave vectors τ , peak intensities I , and correlation lengths λ measured at Mn L 2 -, O K -, and Dy M 5 -edges, we show that the nearly perfect locking between the ordering wave vectors from Dy 4 f states and Mn 3 d orbitals manifesting the second harmonic diffraction peak implies the notable orbital involvement in the coupling between Mn and Dy spins. Our DFT calculations further suggest that the lattice response to different antiferromagnetic ground states (A-type versus E-type) is much weaker in TbMnO 3 , in agreement with previous claim that the symmetric exchange interaction can be an important factor for understanding the ferroelectricity in DyMnO 3 than in TbMnO 3 .
- Published
- 2021
22. Unraveling the Origin of Visible Light Capture by Core–Shell TiO2 Nanotubes
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Zhi-Qiang Wang, Sui-Dong Wang, Y. C. Shao, Way-Faung Pong, Tsun-Kong Sham, Jinghua Guo, Jun Li, Xueliang Sun, Changhai Liu, and Xia Li
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Anatase ,Materials science ,Scattering ,General Chemical Engineering ,Analytical chemistry ,Heterojunction ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease_cause ,01 natural sciences ,XANES ,0104 chemical sciences ,Amorphous solid ,Nuclear magnetic resonance ,X-ray photoelectron spectroscopy ,Materials Chemistry ,medicine ,0210 nano-technology ,Ultraviolet ,Visible spectrum - Abstract
A black TiO2 nanotube (NT) heterostructure with an anatase-core and an amorphous-shell has been synthesized by NH3 annealing of amorphous NT grown by the anodization of a Ti substrate. Remarkable photoabsorption behavior of these black TiO2 NTs is observed: strong absorption throughout the entire optical wavelength region from ultraviolet to near-infrared. X-ray absorption near-edge structure (XANES), X-ray photoelectron spectroscopy (XPS) and resonant inelastic X-ray scattering (RIXS) have been used to elucidate the origin of this spectacular light capture phenomenon. Surface-sensitive XANES recorded in total electron yield and XPS show that the surface layer is amorphous with a chemical composition approaching that of Ti4O7. Bulk-sensitive XANES using X-ray partial fluorescence yield and Ti 2p RIXS confirm the presence of a rich amount of Ti3+ in the crystalline bulk (core of the NT with anatase structure) of black TiO2 NTs, which exhibits a dispersive d-d energy loss at ∼2 eV corresponding to the broad...
- Published
- 2016
23. Reproducibly creating hierarchical 3D carbon to study the effect of Si surface functionalization on the oxygen reduction reaction
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Jennifer Q. Lu, Yi-De Chuang, Y. C. Shao, Jinghua Guo, Jose F. Flores, and Yuze Zeng
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Materials science ,Carbon nanofiber ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,Electronic structure ,Current collector ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,Electrocatalyst ,01 natural sciences ,0104 chemical sciences ,chemistry ,Oxygen reduction reaction ,Surface modification ,General Materials Science ,0210 nano-technology ,Carbon - Abstract
We report a new method to reproducibly fabricate functional 3D carbon structures directly on a current collector, e.g. stainless steel. The 3D carbon platform is formed by direct growth of upright arrays of carbon nanofiber bundles on a roughened surface of stainless steel via the seed-assisted approach. Each bundle consists of about 30 individual carbon nanofibers with a diameter of 18 nm on average. We have found that this new platform offers adequate structural integrity. As a result, no reduction of the surface area during downstream chemical functionalization was observed. With a fixed and reproducible 3D structure, the effect of the chemistry of the grafted species on the oxygen reduction reaction has been systematically investigated. This investigation reveals for the first time that non-conductive Si with an appropriate electronic structure distorts the carbon electronic structure and consequently enhances ORR electrocatalysis. The strong interface provides excellent electron connectivity according to electrochemical analysis. This highly reproducible and stable 3D platform can serve as a stepping-stone for the investigation of the effect of carbon surface functionalization on electrochemical reactions in general.
- Published
- 2016
24. The key energy scales of Gd-based metallofullerene determined by resonant inelastic X-ray scattering spectroscopy
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Jinghua Guo, Shangfeng Yang, Yi-De Chuang, S. W. Huang, Y. C. Shao, L. Andrew Wray, Yi-Sheng Liu, Wang Song, and Way-Faung Pong
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Fullerene ,Materials science ,Proton ,Science ,02 engineering and technology ,Electronic structure ,01 natural sciences ,Molecular physics ,Spectral line ,Article ,chemistry.chemical_compound ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,010306 general physics ,Spectroscopy ,Multidisciplinary ,Scattering ,021001 nanoscience & nanotechnology ,Other Physical Sciences ,Resonant inelastic X-ray scattering ,chemistry ,Metallofullerene ,Biomedical Imaging ,Medicine ,Biochemistry and Cell Biology ,0210 nano-technology - Abstract
Endohedral metallofullerenes, formed by encaging Gd inside fullerenes like C80, can exhibit enhanced proton relaxitivities compared with other Gd-chelates, making them the promising contrast agents for magnetic resonance imaging (MRI). However, the underlying key energy scales of Gd x Sc3−x N@C80 (x = 1–3) remain unclear. Here, we carry out resonant inelastic x-ray scattering (RIXS) experiments on Gd x Sc3−x N@C80 at Gd N4,5-edges to directly study the electronic structure and spin flip excitations of Gd 4f electrons. Compared with reference Gd2O3 and contrast agent Gadodiamide, the features in the RIXS spectra of all metallofullerenes exhibit broader spectral lineshape and noticeable energy shift. Using atomic multiplet calculations, we have estimated the key energy scales such as the inter-site spin exchange field, intra-atomic 4f–4f Coulomb interactions, and spin-orbit coupling. The implications of these parameters to the 4f states of encapsulated Gd atoms are discussed.
- Published
- 2017
25. Magnetic anisotropic properties of Pd/Co/Pd trilayer films studied by X-ray absorption spectroscopy and magnetic circular dichroism
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Y. F. Wang, Wen Chin Lin, K. Saravanan, Y. C. Shao, Bo-Yao Wang, H. M. Tsai, C. H. Kao, H.-J. Lin, L. Y. Jang, C. J. Tsai, H. T. Wang, W. F. Pong, J. F. Lee, and C. W. Pao
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X-ray absorption spectroscopy ,Materials science ,Extended X-ray absorption fine structure ,Magnetic circular dichroism ,Annealing (metallurgy) ,General Chemical Engineering ,Analytical chemistry ,General Chemistry ,XANES ,Condensed Matter::Materials Science ,Crystallography ,Edge structure ,Condensed Matter::Superconductivity ,Anisotropy ,Spectroscopy - Abstract
We study the magnetic anisotropic properties of as-grown and annealed Pd/Co/Pd trilayer films based on their atomic and electronic structures using extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES) spectroscopy and magnetic circular dichroism (XMCD) measurements. The annealed film exhibits interesting perpendicular magnetic anisotropy (PMA) whereas the as-grown film exhibits in-plane anisotropy. Cross-sectional transmission electron microscopic analysis together with the Co K-edge EXAFS results confirm the formation of an ordered-alloy CoPd phase in the annealed film, whereas the as-grown film has an hcp Co-like phase. Co L3,2-edge XMCD measurements reveal an enhanced ratio of the Co 3d orbital to spin moments of the annealed film providing evidence of the observed PMA upon annealing.
- Published
- 2015
26. Anisotropy in the thermal hysteresis of resistivity and charge density wave nature of single crystal SrFeO3-δ: X-ray absorption and photoemission studies
- Author
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Fangcheng Chou, J.-L. Chen, S. H. Lee, H. J. Lin, C. W. Pao, J. W. Chiou, J. F. Lee, C.-M. Cheng, C. H. Yao, S. H. Hsieh, R. S. Solanki, H. T. Wang, W. F. Pong, W.-C. Chen, Y. C. Shao, H. M. Tsai, Y. F. Wang, Y. Y. Chin, and Chao-Hung Du
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Multidisciplinary ,Materials science ,Condensed matter physics ,Photoemission spectroscopy ,Band gap ,Transition temperature ,Science ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Bond length ,Electrical resistivity and conductivity ,0103 physical sciences ,Medicine ,010306 general physics ,0210 nano-technology ,Anisotropy ,Charge density wave ,Single crystal - Abstract
The local electronic and atomic structures of the high-quality single crystal of SrFeO3-δ (δ~0.19) were studied using temperature-dependent x-ray absorption and valence-band photoemission spectroscopy (VB-PES) to investigate the origin of anisotropic resistivity in the ab-plane and along the c-axis close to the region of thermal hysteresis (near temperature for susceptibility maximum, Tm~78 K). All experiments herein were conducted during warming and cooling processes. The Fe L3,2-edge X-ray linear dichroism results show that during cooling from room temperature to below the transition temperature, the unoccupied Fe 3d eg states remain in persistently out-of-plane 3d3z2-r2 orbitals. In contrast, in the warming process below the transition temperature, they change from 3d3z2-r2 to in-plane 3dx2-y2 orbitals. The nearest-neighbor (NN) Fe-O bond lengths also exhibit anisotropic behavior in the ab-plane and along the c-axis below Tm. The anisotropic NN Fe-O bond lengths and Debye-Waller factors stabilize the in-plane Fe 3dx2-y2 and out-of-plane 3d3z2-r2 orbitals during warming and cooling, respectively. Additionally, a VB-PES study further confirms that a relative band gap opens at low temperature in both the ab-plane and along the c-axis, providing the clear evidence of the charge-density-wave nature of SrFeO3-δ (δ~0.19) single crystal.
- Published
- 2017
- Full Text
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27. Origin of magnetic properties in carbon implanted ZnO nanowires
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Hung-Ju Lin, H. T. Wang, W. F. Pong, Jih-Jen Wu, Sekhar C. Ray, C. W. Pao, J. W. Chiou, Keun Hwa Chae, C. T. Wu, Y. F. Wang, Toshihiko Yokoyama, Jyh-Fu Lee, Yu-Yung Chang, Yasumasa Takagi, Takuji Ohigashi, H. M. Tsai, K. Asokan, Y. C. Shao, H. C. Hsueh, S. H. Hsieh, Y. K. Chang, Ping-Hung Yeh, C. H. Chen, and Nobuhiro Kosugi
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Multidisciplinary ,Photoluminescence ,Materials science ,Spin polarization ,Magnetic circular dichroism ,Condensed Matter::Other ,lcsh:R ,Analytical chemistry ,lcsh:Medicine ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Magnetic hysteresis ,01 natural sciences ,Article ,Ion ,Magnetization ,Condensed Matter::Materials Science ,Ion implantation ,Ferromagnetism ,0103 physical sciences ,lcsh:Q ,010306 general physics ,0210 nano-technology ,lcsh:Science - Abstract
Various synchrotron radiation-based spectroscopic and microscopic techniques are used to elucidate the room-temperature ferromagnetism of carbon-doped ZnO-nanowires (ZnO-C:NW) via a mild C+ ion implantation method. The photoluminescence and magnetic hysteresis loops reveal that the implantation of C reduces the number of intrinsic surface defects and increases the saturated magnetization of ZnO-NW. The interstitial implanted C ions constitute the majority of defects in ZnO-C:NW as confirmed by the X-ray absorption spectroscopic studies. The X-ray magnetic circular dichroism spectra of O and C K-edge respectively indicate there is a reduction in the number of unpaired/dangling O 2p bonds in the surface region of ZnO-C:NW and the C 2p-derived states of the implanted C ions strongly affect the net spin polarization in the surface and bulk regions of ZnO-C:NW. Furthermore, these findings corroborate well with the first-principles calculations of C-implanted ZnO in surface and bulk regions, which highlight the stability of implanted C for the suppression and enhancement of the ferromagnetism of the ZnO-C:NW in the surface region and bulk phase, respectively.
- Published
- 2017
28. Electronic and atomic structures of the Sr3Ir4Sn13 single crystal: A possible charge density wave material
- Author
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Chin-Shan Lue, S. H. Hsieh, H. T. Wang, W. F. Pong, M. K. Srivastava, Chao-Hung Du, J. W. Chiou, J. L. Chen, Y. F. Wang, Y. C. Shao, Y. H. Liang, C. W. Pao, Maw-Kuen Wu, J. F. Lee, C. N. Kuo, C. C. Wu, and Ching Cheng
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Multidisciplinary ,Materials science ,Extended X-ray absorption fine structure ,Scattering ,Transition temperature ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Article ,XANES ,Spectral line ,Electrical resistivity and conductivity ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Single crystal ,Charge density wave - Abstract
X-ray scattering (XRS), x-ray absorption near-edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectroscopic techniques were used to study the electronic and atomic structures of the high-quality Sr3Ir4Sn13 (SIS) single crystal below and above the transition temperature (T* ≈ 147 K). The evolution of a series of modulated satellite peaks below the transition temperature in the XRS experiment indicated the formation of a possible charge density wave (CDW) in the (110) plane. The EXAFS phase derivative analysis supports the CDW-like formation by revealing different bond distances [Sn1(2)-Sn2] below and above T* in the (110) plane. XANES spectra at the Ir L3-edge and Sn K-edge demonstrated an increase (decrease) in the unoccupied (occupied) density of Ir 5d-derived states and a nearly constant density of Sn 5p-derived states at temperatures T * in the (110) plane. These observations clearly suggest that the Ir 5d-derived states are closely related to the anomalous resistivity transition. Accordingly, a close relationship exists between local electronic and atomic structures and the CDW-like phase in the SIS single crystal.
- Published
- 2017
29. Modular soft x-ray spectrometer for applications in energy sciences and quantum materials
- Author
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Valeriy V. Yashchuk, Ruimin Qiao, L. Andrew Wray, Brian M. Smith, Robert Duarte, Wanli Yang, Yi-De Chuang, Jinghua Guo, Edward E. Domning, Y. C. Shao, Zahid Hussain, S. W. Huang, Thomas P. Devereaux, Alex Frano, Kelly Hanzel, Adam Brown, Wei-Sheng Lee, Ruben Reininger, Jaw Wern Chiou, Alejandro G. Cruz, Zhi-Xun Shen, Way-Faung Pong, and Eric M. Gullikson
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Materials science ,Photon ,Spectrometer ,business.industry ,Detector ,02 engineering and technology ,Grating ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,Optics ,Engineering ,Affordable and Clean Energy ,0103 physical sciences ,Physical Sciences ,Chemical Sciences ,Emission spectrum ,Spectral resolution ,010306 general physics ,0210 nano-technology ,business ,Instrumentation ,Diffraction grating ,Applied Physics - Abstract
© 2017 Author(s). Over the past decade, the advances in grating-based soft X-ray spectrometers have revolutionized the soft X-ray spectroscopies in materials research. However, these novel spectrometers are mostly dedicated designs, which cannot be easily adopted for applications with diverging demands. Here we present a versatile spectrometer design concept based on the Hettrick-Underwood optical scheme that uses modular mechanical components. The spectrometer’s optics chamber can be used with gratings operated in either inside or outside orders, and the detector assembly can be reconfigured accordingly. The spectrometer can be designed to have high spectral resolution, exceeding 10 000 resolving power when using small source (∼1μm) and detector pixels (∼5μm) with high line density gratings (∼3000 lines/mm), or high throughput at moderate resolution. We report two such spectrometers with slightly different design goals and optical parameters in this paper. We show that the spectrometer with high throughput and large energy window is particularly useful for studying the sustainable energy materials. We demonstrate that the extensive resonant inelastic X-ray scattering (RIXS) map of battery cathode material LiNi1/3Co1/3Mn1/3O2 can be produced in few hours using such a spectrometer. Unlike analyzing only a handful of RIXS spectra taken at selected excitation photon energies across the elemental absorption edges to determine various spectral features like the localized dd excitations and non-resonant fluorescence emissions, these features can be easily identified in the RIXS maps. Studying such RIXS maps could reveal novel transition metal redox in battery compounds that are sometimes hard to be unambiguously identified in X-ray absorption and emission spectra. We propose that this modular spectrometer design can serve as the platform for further customization to meet specific scientific demands.
- Published
- 2017
30. Low temperature magneto-transport properties in bilayered magnetic anti-dot mircoarrays
- Author
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M. S. Seo, Way-Faung Pong, N.G. Deshpande, Y. C. Shao, J. S. Hwang, Kuei-Hsien Chen, Youngbin Lee, Y.J. Yoo, J.Y. Rhee, and K.W. Kim
- Subjects
Materials science ,Magnetoresistance ,Condensed matter physics ,Absorption spectroscopy ,Bilayer ,General Physics and Astronomy ,chemistry.chemical_element ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films ,X-ray absorption fine structure ,Nickel ,Exchange bias ,chemistry ,Anisotropy ,Cobalt - Abstract
Magneto-transport study on the photolithographically-patterned anti-dot micro-arrays of cobalt upper-layer over a uniform thin nickel under-layer has been carried out. Circular anti-dots in rhomboidal symmetry were fabricated. The magnetoresistance (MR) curves were recorded for magnetically-easy and -hard axes of the bilayer structure at various temperatures. In addition to anisotropic MR, at low temperatures, the MR data shows anomalous behavior with several kinks and plateau regions, indicating complex reversal phenomena. Further, decrease in temperature results in increase of MR average peak height, double splitting of MR peaks and broadening of MR peaks. Additionally, the exchange bias behavior was found in the transverse MR curve; while no significant exchange effect was seen in the longitudinal MR curve. Using energy dispersive spectrum and X-ray absorption spectra taken at Co L3,2-edge, the presence of CoO layer over the bilayer structure was detected; while the Ni under-layer remained deoxidized.
- Published
- 2014
31. Spectroscopic investigation of an intrinsic room temperature ferromagnetism in Co doped ZnO nanoparticles
- Author
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N. Srinatha, Way-Faung Pong, K.G.M. Nair, Nishad G. Deshpande, Y. C. Shao, and Basavaraj Angadi
- Subjects
Radiation ,Valence (chemistry) ,Magnetic circular dichroism ,Analytical chemistry ,Electronic structure ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,XANES ,Electronic, Optical and Magnetic Materials ,Condensed Matter::Materials Science ,Ferromagnetism ,Impurity ,Physical and Theoretical Chemistry ,Spectroscopy ,Wurtzite crystal structure ,Diffractometer - Abstract
Pure and Co substituted ZnO nano crystalline particles were prepared by solution combustion technique using l -Valine as a fuel. As synthesized powder samples were characterized by X-ray diffractometer and SQUID magnetometer to confirm the formation of single phase wurtzite structure and to study the bulk magnetic response of the sample, respectively. Magnetic studies show that Co doped ZnO nanoparticles exhibit ferromagnetism (FM) at room temperature (RT). Furthermore, the electronic structure and element specific magnetic properties were investigated by near-edge X-ray absorption fine structure (NEXAFS) and X-ray magnetic circular dichroism (XMCD) measurements, respectively. The effect of Co substitution on the spectral features of Co–ZnO at O K -edge, Co L 3,2 edge, Zn L 3,2 edge have been investigated. The spectral features of NEXAFS at Co L 3,2 edge is entirely different from the spectral features of metallic clusters and other impurity phases, which rules out the presence of impurity phases. The valence state of ‘Co’ ion is found to be in +2 state. The FM nature of the sample was confirmed through XMCD spectra, which is due to the incorporation of divalent ‘Co’ ions. Hence the presented results confirm the substitution of ‘Co’ ions at ‘Zn’ site in the host lattice, which is responsible for the RTFM.
- Published
- 2014
32. Probing the Electronic Structure of BiVO4 Coated ZnO Nanodendrite Core- Shell Nanocomposite Using X-ray Spectroscopic and Spatially Resolved Scanning Transmission X-ray Microscopy Studies
- Author
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Jih-Sheng Yang, H. T. Wang, Mandar M. Shirolkar, Way-Faung Pong, Jih-Jen Wu, Yu-Fu Wang, Takuji Ohigashi, Jau-Wern Chiou, Kuan-Hung Chen, Y. C. Shao, Nobuhiro Kosugi, and Xian-Sheng Qiu
- Subjects
Nanocomposite ,Materials science ,Spatially resolved ,Analytical chemistry ,X-ray ,02 engineering and technology ,Electronic structure ,Scanning transmission X-ray microscopy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Core shell ,0210 nano-technology ,Instrumentation - Published
- 2018
33. Anisotropy in the thermal hysteresis of resistivity and charge density wave nature of single crystal SrFeO
- Author
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S H, Hsieh, R S, Solanki, Y F, Wang, Y C, Shao, S H, Lee, C H, Yao, C H, Du, H T, Wang, J W, Chiou, Y Y, Chin, H M, Tsai, J-L, Chen, C W, Pao, C-M, Cheng, W-C, Chen, H J, Lin, J F, Lee, F C, Chou, and W F, Pong
- Subjects
Article - Abstract
The local electronic and atomic structures of the high-quality single crystal of SrFeO3-δ (δ~0.19) were studied using temperature-dependent x-ray absorption and valence-band photoemission spectroscopy (VB-PES) to investigate the origin of anisotropic resistivity in the ab-plane and along the c-axis close to the region of thermal hysteresis (near temperature for susceptibility maximum, Tm~78 K). All experiments herein were conducted during warming and cooling processes. The Fe L 3,2-edge X-ray linear dichroism results show that during cooling from room temperature to below the transition temperature, the unoccupied Fe 3d e g states remain in persistently out-of-plane 3d 3z 2 -r 2 orbitals. In contrast, in the warming process below the transition temperature, they change from 3d 3z 2 -r 2 to in-plane 3d x 2 -y 2 orbitals. The nearest-neighbor (NN) Fe-O bond lengths also exhibit anisotropic behavior in the ab-plane and along the c-axis below Tm. The anisotropic NN Fe-O bond lengths and Debye-Waller factors stabilize the in-plane Fe 3d x 2 -y 2 and out-of-plane 3d 3z 2 -r 2 orbitals during warming and cooling, respectively. Additionally, a VB-PES study further confirms that a relative band gap opens at low temperature in both the ab-plane and along the c-axis, providing the clear evidence of the charge-density-wave nature of SrFeO3-δ (δ~0.19) single crystal.
- Published
- 2016
34. Prominent role of oxygen in the multiferroicity ofDyMnO3andTbMnO3: A resonant soft x-ray scattering spectroscopy study
- Author
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Horng-Tay Jeng, L. Andrew Wray, Ruimin Qiao, Jin-Ming Chen, J. M. Lee, S. W. Huang, Y.-D. Chuang, Y. C. Shao, Yue Cao, Wanli Yang, Robert W. Schoenlein, and Jiunn-Yuan Lin
- Subjects
Physics ,Spins ,Condensed matter physics ,Scattering ,Orbital hybridisation ,Exchange interaction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,K-edge ,Atomic orbital ,0103 physical sciences ,Antiferromagnetism ,010306 general physics ,0210 nano-technology ,Spectroscopy - Abstract
Oxygen is known to play an important role in the multiferroicity of rare earth manganites; however, how this role changes with rare earth elements is still not fully understood. To address this question, we have used resonant soft x-ray scattering spectroscopy to study the F-type (0,τ,0) diffraction peak from the antiferromagnetic order in DyMnO3 and TbMnO3. We focus on the measurements at O K edge of these two manganites, supplemented by the results at Mn L2 and Dy M5 edge of DyMnO3. We show that the electronic states of different elements are coupled more strongly in DyMnO3 than in TbMnO3, presumably due to the stronger lattice distortion and the tendency to develop E-type antiferromagnetism in the ferroelectric state that promote the orbital hybridization. We also show that the anomaly in the correlation length of (0,τ,0) peak in DyMnO3 signifies the exchange interaction between Mn and rare earth spins. Our findings reveal the prominent role of oxygen orbitals in the multiferroicity of rare earth manganites and the distinct energetics between them.
- Published
- 2016
35. Influence of Dynamic Disturbance on Evolvement and Stability of Rock Mechanics System
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Y. C. Shao and Peng Shao
- Subjects
Disturbance (geology) ,Rock mechanics ,Geotechnical engineering ,Stability (probability) ,Geology - Published
- 2016
36. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques
- Author
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Mukta V. Limaye, C. Y. Lee, L. Y. Jang, Shashi B. Singh, J. W. Chiou, W. F. Pong, Y. C. Shao, S. C. Chen, H. C. Hsueh, Yongfeng Hu, S. H. Hsieh, Y. F. Wang, C. H. Chen, L. Y. Chen, and Chia-Liang Cheng
- Subjects
Condensed Matter::Materials Science ,Multidisciplinary ,Materials science ,X-ray photoelectron spectroscopy ,Extended X-ray absorption fine structure ,Photoemission spectroscopy ,Band gap ,Femtosecond ,Absorptance ,Analytical chemistry ,Spectroscopy ,XANES ,Article - Abstract
The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2− (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2− species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2−, n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples.
- Published
- 2014
37. The effect of thermal reduction on the photoluminescence and electronic structures of graphene oxides
- Author
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Yu-Te Yeh, Jinghua Guo, Sekhar C. Ray, C. W. Chen, Junfa Zhu, Di Yan Wang, J. W. Chiou, Cynthia H. Chuang, Y. F. Wang, Y. C. Shao, Liang Zhang, and Way-Faung Pong
- Subjects
Multidisciplinary ,Photoluminescence ,Materials science ,Graphene ,Analytical chemistry ,Oxide ,XANES ,Article ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Density of states ,Pyrolytic carbon ,Emission spectrum ,Absorption (electromagnetic radiation) - Abstract
Electronic structures of graphene oxide (GO) and hydro-thermally reduced graphene oxides (rGOs) processed at low temperatures (120-180°C) were studied using X-ray absorption near-edge structure (XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). C K-edge XANES spectra of rGOs reveal that thermal reduction restores C = C sp(2) bonds and removes some of the oxygen and hydroxyl groups of GO, which initiates the evolution of carbonaceous species. The combination of C K-edge XANES and Kα XES spectra shows that the overlapping π and π* orbitals in rGOs and GO are similar to that of highly ordered pyrolytic graphite (HOPG), which has no band-gap. C Kα RIXS spectra provide evidence that thermal reduction changes the density of states (DOSs) that is generated in the π-region and/or in the gap between the π and π* levels of the GO and rGOs. Two-dimensional C Kα RIXS mapping of the heavy reduction of rGOs further confirms that the residual oxygen and/or oxygen-containing functional groups modify the π and σ features, which are dispersed by the photon excitation energy. The dispersion behavior near the K point is approximately linear and differs from the parabolic-like dispersion observed in HOPG.
- Published
- 2014
38. Atomic-scale observation of a graded polar discontinuity and a localized two-dimensional electron density at an insulating oxide interface
- Author
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C. P. Chang, Y. C. Shao, Chung-Hsuan Chen, Jauyn Grace Lin, Horng-Tay Jeng, Ming-Wen Chu, Jer-Ren Yang, W. F. Pong, Hung-Ju Lin, Chun-Wei Chen, Yi Ying Chin, and S. L. Cheng
- Subjects
Length scale ,Electron density ,Materials science ,Condensed matter physics ,Electron energy loss spectroscopy ,Charge density ,Electron ,Condensed Matter Physics ,Fermi gas ,Spectroscopy ,Atomic units ,Electronic, Optical and Magnetic Materials - Abstract
Using atomically resolved electron energy-loss spectroscopy, the atomic-plane-by-atomic-plane, unit-cell-by-unit-cell stoichiometry, and charge characteristics of the oxide interface (Nd${}_{0.35}$Sr${}_{0.65}$)MnO${}_{3}$/SrTiO${}_{3}$, with a primitive polar discontinuity of (Nd${}_{0.35}$Sr${}_{0.65}$O)${}^{0.35+}$-(TiO${}_{2}$)${}^{0}$, were thoroughly investigated. (Nd${}_{0.35}$Sr${}_{0.65}$)MnO${}_{3}$ is a strongly correlated insulator and the interface was characterized to be insulating. The cell-specific stoichiometric evaluation unveiled an extensive interdiffusion across the interface. The plane-specific charge characterization revealed that the interdiffusion grades the primitive polar discontinuity. Despite the graded polar discontinuity, a charge transfer inversely into (Nd${}_{0.35}$Sr${}_{0.65}$)MnO${}_{3}$ was firmly resolved with a length scale of \ensuremath{\sim}2 nm and a charge density on the order of \ensuremath{\sim}10${}^{13}$/cm${}^{2}$ and is effectively mediated by an asymmetric Ti interdiffusion. The intricate electronic correlations of the interfacial (Nd${}_{0.35}$Sr${}_{0.65}$)MnO${}_{3}$ unit cells and the interdiffusion-induced chemical disorder tend to render the charges localized, resulting in a localized two-dimensional electron density and thus the insulating interface, in distinct contrast to the conventional understanding of a vanishing charge density for an insulating interface and the metallic two-dimensional electron gas found at other classical polar-discontinuous interface systems. A potential strain manipulation on the electronic localization of the electron density was also proposed.
- Published
- 2013
39. Correlation betweenp-type conductivity and electronic structure of Cr-deficient CuCr1−xO2(x=0--0.1)
- Author
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Shashi B. Singh, L. T. Yang, Nobuhiro Kosugi, Hung-Ju Lin, Bo-Yao Wang, C. H. Chen, S. C. Chen, M.-H. Tsai, Cheng-Hao Chuang, Y. C. Shao, Y. F. Wang, K. T. Lin, W. F. Pong, Jyh-Fu Lee, C. W. Chiang, C. W. Pao, H. W. Shiu, H. M. Tsai, J. W. Chiou, D. C. Ling, and Hiroyuki Yamane
- Subjects
Materials science ,Valence (chemistry) ,Fermi level ,Electronic structure ,Condensed Matter Physics ,Variable-range hopping ,Spectral line ,XANES ,Electronic, Optical and Magnetic Materials ,symbols.namesake ,Crystallography ,symbols ,Emission spectrum ,Absorption (logic) - Abstract
The correlation between the $p$-type hole conduction and the electronic structures of Cr-deficient CuCr${}_{1\ensuremath{-}x}$O${}_{2}$ ($x=0\ensuremath{-}0.1$) compounds was investigated using O $K$-, Cu, and Cr ${L}_{3,2}$-edge x-ray absorption near-edge structure (XANES), scanning photoelectron microscopy, and x-ray emission spectroscopy measurements. XANES spectra reveal a gradual increase in the Cu valence from Cu${}^{1+}$ to Cu${}^{2+}$ with increasing Cr deficiency $x$, whereas, the valence of Cr remains constant as Cr${}^{3+}$. These results indicate that the $p$-type conductivity in the CuCr${}_{1\ensuremath{-}x}$O${}_{2}$ samples is enhanced by a Cu${}^{1+}$-O-Cu${}^{2+}$ rather than a Cr${}^{3+}$-Cr${}^{4+}$ or direct Cu${}^{1+}$-Cu${}^{2+}$ hole mechanism. Remarkable Cr-deficiency-induced changes in the densities of Cu 3$d$, Cu 3$d$-O 2$p$, and O 2$p$ states at or near the valence-band maximum or the Fermi level were also observed. In addition, a crossover of conduction mechanism from thermally activated (TA) hopping to a combination of TA and Mott's three-dimensional variable range hopping occurs around 250 K.
- Published
- 2012
40. Nitrogen-Functionalized Graphene Nanoflakes (GNFs:N): Tunable Photoluminescence and Electronic Structures
- Author
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Sekhar C. Ray, Way-Faung Pong, M.-H. Tsai, Kuei-Hsien Chen, S. C. Chen, Tsun-Kong Sham, J. W. Chiou, Chin-Pei Chen, C. W. Pao, Tom Regier, Yu-Chang Yeh, Abhijit Ganguly, Cynthia H. Chuang, Li-Chyong Chen, Pagona Papakonstantinou, Y. C. Shao, Yanzhong Wang, Ajay Kumar, Hiroyuki Yamane, S. I. Peng, Bo-Yao Wang, Nobuhiro Kosugi, Lijia Liu, H. M. Tsai, and Hong-Ji Lin
- Subjects
Condensed Matter - Materials Science ,Photoluminescence ,Materials science ,Graphene ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,Molecular physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Blueshift ,General Energy ,law ,Excited state ,Density of states ,Emission spectrum ,Physical and Theoretical Chemistry ,Luminescence ,Absorption (electromagnetic radiation) - Abstract
This study investigates the strong photoluminescence (PL) and X-ray excited optical luminescence observed in nitrogen-functionalized 2D graphene nanoflakes (GNFs:N), which arise from the significantly enhanced density of states in the region of {\pi} states and the gap between {\pi} and {\pi}* states. The increase in the number of the sp2 clusters in the form of pyridine-like N-C, graphite-N-like, and the C=O bonding and the resonant energy transfer from the N and O atoms to the sp2 clusters were found to be responsible for the blue shift and the enhancement of the main PL emission feature. The enhanced PL is strongly related to the induced changes of the electronic structures and bonding properties, which were revealed by the X-ray absorption near-edge structure, X-ray emission spectroscopy, and resonance inelastic X-ray scattering. The study demonstrates that PL emission can be tailored through appropriate tuning of the nitrogen and oxygen contents in GNFs and pave the way for new optoelectronic devices., Comment: 8 pages, 6 figures (including toc figure)
- Published
- 2012
41. P3P-6 Modeling and Design of a Linear Actuator by Langevin Vibrators
- Author
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Y. C. Shao, Yung Ting, Chieh-Min Yang, J. M. Yang, and Chun-Chung Li
- Subjects
ComputingMilieux_GENERAL ,Generator (circuit theory) ,Physics ,Transducer ,Acoustics ,Traveling wave ,Modeling and design ,Linear actuator ,Linear motor ,Actuator ,Vibrator (mechanical) - Abstract
A linear actuator driven by traveling wave generated by a pair of Langevin vibrators is designed. While one vibrator is assigned as the wave generator and the other one as the absorber, vibrators propel the rail to generate traveling wave so as to drive a guide mounted above. Comprehensive analysis of the Langevin vibrator and the rail is carried out by ANSYS, thus the design is optimized. Practical experiment is completed and the experimental data verify its performance of high speed and large load bearing
- Published
- 2006
42. Radial nerve palsy associated with fractures of the shaft of the humerus: a systematic review
- Author
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Y. C. Shao, M. Grotz, D. Limb, Peter V. Giannoudis, and Paul Harwood
- Subjects
medicine.medical_specialty ,Humeral Fractures ,Radial neuropathy ,Neurological disorder ,Paralysis ,Medicine ,Humans ,Orthopedics and Sports Medicine ,Humerus ,Radial nerve ,Palsy ,business.industry ,Significant difference ,Recovery of Function ,medicine.disease ,Prognosis ,Surgery ,medicine.anatomical_structure ,Treatment Outcome ,Orthopedic surgery ,Practice Guidelines as Topic ,Radial Nerve ,medicine.symptom ,Radial Neuropathy ,business ,Algorithms - Abstract
The management of radial nerve palsy associated with fractures of the shaft of the humerus has been disputed for several decades. This study has systematically reviewed the published evidence and developed an algorithm to guide management. We searched web-based databases for studies published in the past 40 years and identified further pages through manual searches of the bibliography in papers identified electronically. Of 391 papers identified initially, encompassing a total of 1045 patients with radial nerve palsy, 35 papers met all our criteria for eligibility. Meticulous extraction of the data was carried out according to a preset protocol. The overall prevalence of radial nerve palsy after fracture of the shaft of the humerus in 21 papers was 11.8% (532 palsies in 4517 fractures). Fractures of the middle and middle-distal parts of the shaft had a significantly higher association with radial nerve palsy than those in other parts. Transverse and spiral fractures were more likely to be associated with radial nerve palsy than oblique and comminuted patterns of fracture (p < 0.001). The overall rate of recovery was 88.1% (921 of 1045), with spontaneous recovery reaching 70.7% (411 of 581) in patients treated conservatively. There was no significant difference in the final results when comparing groups which were initially managed expectantly with those explored early, suggesting that the initial expectant treatment did not affect the extent of nerve recovery adversely and would avoid many unnecessary operations. A treatment algorithm for the management of radial nerve palsy associated with fracture of the shaft of the humerus is recommended by the authors.
- Published
- 2005
43. The electronic and magnetic properties of strained La0.85Zr0.15MnO3films
- Author
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D. C. Ling, Y. F. Wang, C. H. Weng, C. H. Du, H. C. Hsueh, W. F. Pong, Y. C. Shao, and N. G. Deshpande
- Subjects
Inorganic Chemistry ,Structural Biology ,General Materials Science ,Physical and Theoretical Chemistry ,Condensed Matter Physics ,Biochemistry - Abstract
The electronic and magnetic properties of strained tetravalent-ion-doped La0.85Zr0.15MnO3 (LZMO) thin films that were epitaxially grown on SrTiO3 (STO) and MgO substrates were studied using temperature-dependent x-ray diffraction (XRD), x-ray absorption near-edge structure (XANES), x-ray linear dichroism (XLD) and x-ray magnetic circular dichroism (XMCD) at the Mn L3,2- and K-edge. XRD studies reveal that the LZMO thin films have compressive and tensile strains on the STO and MgO substrates, respectively. As temperature is reduced from room temperature to below magnetic transition temperature, the preferentially occupied Mn majority-spin eg orbital changes from the in-plane dx2-y2 to the out-of-plane d3z2-r2 orbital for LZMO/STO, and vice versa for LZMO/MgO. Experimental results suggest that the new hopping path that is mediated by the Mn2+ ions triggers a stronger d3z2-r2 orbital ordering of Mn3+ ions and enhances the ferromagnetic coupling between the Mn spin moments of t2g electrons in LZMO/STO, whereas the tensile strain stabilizes the dx2-y2 orbital by inducing lattice distortions of the MnO6 octahedra in LZMO/MgO.
- Published
- 2014
44. Effect of thickness and Si substrate morphology in La0.7Sr0.3MnO3/Si thin films
- Author
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W.. Pong, S.-H. Hsieh, S.B. Singh, J.-F. Lee, H.-T. Wang, Y.-C. Shao, Y.-F. Wang, H.-M. Tsai, J.-G. Lin, C.-W. Chong, H.-J. Lin, and M.K. Wu
- Subjects
Materials science ,Morphology (linguistics) ,Condensed matter physics ,Extended X-ray absorption fine structure ,Magnetic moment ,Magnetic circular dichroism ,Shell (structure) ,Condensed Matter Physics ,Biochemistry ,Ion ,Inorganic Chemistry ,Nuclear magnetic resonance ,Structural Biology ,General Materials Science ,Physical and Theoretical Chemistry ,Thin film ,Absorption (chemistry) - Abstract
Investigation has been made on atomic, electronic structures and magnetic properties of La0.7Sr0.3MnO3 (LSMO) on Si substrate. The effect of different thickness of LSMO and different morphological [flat and nano-pyramid (NP)] of Si substrate are studied in present work. The result of Mn K-edge extended x-ray absorption fine structure indicates the more disorder of local atomic structure of first shell (Mn-O bound) in the thinner LSMO/Si film. The Mn L3,2-edge x-ray absorption near-edge structure shows the presence of Mn2+ ion on the sample. Furthermore, the Mn L3,2-edge x-ray magnetic circular dichroism reveals that the thinner film (LSMO/Si) has highest magnetic moment, in comparison to that of thick LSMO/Si and LSMO/Si-NP samples. This finding suggests that the appearance Mn2+ may play an important role in magnetic behavior of hetero-junction LSMnO/Si and Si-NP.
- Published
- 2014
45. Observation of the origin of d0magnetism in ZnO nanostructures using X-ray-based microscopic and spectroscopic techniques
- Author
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S. H. Hsieh, Yu Fu Wang, Jau Wern Chiou, Hsuan Yu Lai, Takuji Ohigashi, Tom Regier, Tsun-Kong Sham, Shashi B. Singh, Jigang Zhou, Chen Hao Chuang, Hung Ming Tsai, H. C. Hsueh, Jyh-Fu Lee, Mukta V. Limaye, Way-Faung Pong, Chih Wen Pao, Chia Hao Chen, Nobuhiro Kosugi, Y. C. Shao, Hsaiotsu Wang, Chun Te Wu, Jih-Jen Wu, Hong-Ji Lin, and Jian Wang
- Subjects
Luminescence ,Photoluminescence ,Materials science ,Surface Properties ,Population ,Magnetics ,symbols.namesake ,Magnetization ,Nanotechnology ,General Materials Science ,education ,education.field_of_study ,Fourier Analysis ,Condensed matter physics ,Nanowires ,Magnetic circular dichroism ,X-Rays ,Fermi level ,Temperature ,Tin Compounds ,XANES ,Nanostructures ,Oxygen ,Crystallography ,X-Ray Absorption Spectroscopy ,Spectrophotometry ,symbols ,Density of states ,Zinc Oxide ,Local-density approximation - Abstract
Efforts have been made to elucidate the origin of d(0) magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites. Specifically, the results of O K-edge scanning transmission X-ray microscopy (STXM) and the corresponding X-ray-absorption near-edge structure (XANES) spectroscopy demonstrated that the impurity (non-stoichiometric) region in ZnO NCs contains a greater defect population than the thick region. The intensity of O K-edge STXM-XANES in the impurity region is more predominant in ZnO NCs than in NWs. The increase in the unoccupied (occupied) density of states at/above (at/below) the conduction-band minimum (valence-band maximum) or the Fermi level is related to the population of defects at the O sites, as revealed by comparing the ZnO NCs to the NWs. The results of O K-edge and Zn L3,2-edge X-ray magnetic circular dichroism demonstrated that the origin of magnetization is attributable to the O 2p orbitals rather than the Zn d orbitals. Further, the local density approximation (LDA) + U verified that vacancies in the form of dangling or unpaired 2p states (due to Zn vacancies) induced a significant local spin moment in the nearest-neighboring O atoms to the defect center, which was determined from the uneven local spin density by analyzing the partial density of states of O 2p in ZnO.
- Published
- 2014
46. The electronic and magnetic properties of La0.85Zr0.15MnO3 deposited on SrTiO3 and MgO substrates
- Author
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C. H. Weng, H. M. Tsai, W. F. Pong, Y. F. Wang, J. W. Chiou, Y. C. Shao, J. F. Lee, D. C. Ling, Nishad G. Deshpande, M.-H. Tsai, H. C. Hsueh, C. Q. Cheng, H. J. Lin, Chao-Hung Du, and C. W. Pao
- Subjects
Crystallography ,Materials science ,Condensed matter physics ,Ferromagnetism ,Magnetic moment ,Magnetic circular dichroism ,Transition temperature ,General Physics and Astronomy ,Thin film ,Dichroism ,Linear dichroism ,XANES - Abstract
The electronic and magnetic properties of tetravalent-ion-doped La0.85Zr0.15MnO3 (LZMO) thin films that were epitaxially grown on SrTiO3 (STO) and MgO substrates were studied using temperature-dependent x-ray diffraction (XRD), x-ray absorption near-edge structure, x-ray linear dichroism, and x-ray magnetic circular dichroism at the Mn L3,2- and K-edge. XRD studies reveal that the LZMO thin films have compressive and tensile strains (along the c-axis) on the STO and MgO substrates, respectively. As the temperature is reduced from room temperature to below magnetic transition temperature, the preferentially occupied Mn majority-spin eg orbital changes from the in-plane dx2-y2 to the out-of-plane d3z2-r2 orbital for LZMO/STO, and vice versa for LZMO/MgO. Experimental results suggest that the new hopping path that is mediated by the Mn2+ ions triggers a stronger d3z2-r2 orbital ordering of Mn3+ ions and enhances the ferromagnetic coupling between the Mn spin moments of t2g electrons in LZMO/STO, whereas the ...
- Published
- 2014
47. Correlation between electrochromism and electronic structures of tungsten oxide films
- Author
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Mukta V. Limaye, J. S. Chen, Shashi B. Singh, Y. C. Shao, Y. F. Wang, C. W. Pao, H. M. Tsai, J. F. Lee, H. J. Lin, J. W. Chiou, M. C. Yang, W. T. Wu, J. J. Wu, M. H. Tsai, and W. F. Pong
- Subjects
Absorption spectroscopy ,Chemistry ,Electrochromism ,General Chemical Engineering ,Intercalation (chemistry) ,Analytical chemistry ,Nanotechnology ,Biasing ,General Chemistry ,Absorption (electromagnetic radiation) ,XANES ,Nanocrystalline material ,Ion - Abstract
The in-situ X-ray absorption spectroscopy of three tungsten oxide films was performed to study the electronic and atomic structures following repeated cycles of coloration and bleaching processes. The transparent tungsten oxide films become deep blue upon intercalation of Li+ ions in the WO6 octahedra when an external electrical bias was applied. These films reverted to transparent when a reverse external electrical bias was applied. W L3-edge X-ray absorption near-edge structure (XANES) measurements of the nanocrystalline and crystalline tungsten oxide films revealed that the intensity of the white-line feature decreases after coloration and recoverably increases after bleaching owing to the filling and unfilling of the W 5d–O 2p conduction band states. The second derivative of the W L3-edge XANES spectra indicated an increase in structural disordering following repeated cycles of coloration and bleaching. However, the extended X-ray absorption fine structure analysis showed that the nearest-neighbor W–O bond distances in the samples overall remain unchanged by coloration and bleaching. The nanocrystalline tungsten oxide film exhibited more effective recovery (∼97% after first cycle) of the electronic structures than the other two crystalline samples in terms of the filling and unfilling of the W 5d–O 2p conduction band states after repeated coloration and bleaching. These results show that the nanocrystalline tungsten oxide sample has superior electrochromic properties to the crystalline samples.
- Published
- 2014
48. Effect of geometry on the magnetic properties of CoFe2O4–PbTiO3 multiferroic composites
- Author
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Haizhu Wang, Shashi B. Singh, Jyh-Fu Lee, Y. C. Shao, J. W. Chiou, W. F. Pong, Hung-Ju Lin, Ping-Hung Yeh, H. M. Tsai, Bo-Yao Wang, Cheng-Hao Chuang, C. W. Pao, C. Y. Tsai, M.-H. Tsai, Wen-Feng Hsieh, and Y. F. Wang
- Subjects
Materials science ,Octahedron ,Magnetic moment ,Extended X-ray absorption fine structure ,Magnetic circular dichroism ,General Chemical Engineering ,Composite number ,Geometry ,Multiferroics ,General Chemistry ,Composite material ,Magnetic hysteresis ,XANES - Abstract
In this study, X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), X-ray magnetic circular dichroism (XMCD) and element- and site-specific magnetic hysteresis (ESMH) are used to elucidate the effect of geometry (0-3- and 2-2-type) on the magnetic properties of CoFe2O4–PbTiO3 (CFO–PTO) multiferroic composites by comparison with those of the reference CFO and PTO powders. Magnetic Co ions in CFO have been confirmed to be located at both the tetrahedral (A)- and octahedral (B)-sites. CFO retains its mixed-spinel structure as verified by the EXAFS, XMCD and ESMH measurements. ESMH measurements further demonstrate that the magnetic moments of Co2+ and Fe3+/Fe2+ cations at both the A- and B-sites in the composites are smaller than those of the CFO powder. The reduction of the magnetic moments in the 2-2-type composite was larger than that in the 0-3-type composite. The reduction of the magnetic moments in the composites was attributable to the formation of anti-phase boundaries owing to the compressive strain in CFO, which is the largest strain in the 2-2-type composite. Based on the Ti L3,2-edge XMCD measurements of the CFO–PTO composites, no induced magnetic moment was observed at the Ti sites in the PTO matrix, excluding the possibility that the Ti ions in the PTO matrix affect the magnetic properties of these CFO–PTO composites.
- Published
- 2013
49. The effect of local lattice distortion on physical properties of hexagonal rubidium tungsten bronze Rb0.23WOy
- Author
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W. F. Pong, J. W. Chiou, F.Z. Chien, S H Wu, D. C. Ling, Y. C. Shao, and Yang-Yuan Chen
- Subjects
Superconductivity ,History ,Condensed matter physics ,Absorption spectroscopy ,chemistry.chemical_element ,Tungsten ,Oxygen ,Computer Science Applications ,Education ,Rubidium ,chemistry ,Electrical resistivity and conductivity ,Orders of magnitude (data) ,Intensity (heat transfer) - Abstract
Superconducting transition temperature Tc and normal-state resistivity as a function of oxygen content for hexagonal tungsten bronze Rb0.23WOy with 2.90 < y < 3.05 were obtained from transport measurements. It is remarkably interesting that Tc enhances about 50% and room-temperature resistivity increases about three orders of magnitude as oxygen content varies from 2.90 to 3.05. The low-temperature specific heat data indicate that the Einstein-like mode associated with Rb vibration has a dimensionality crossover from 3D to quasi-2D as oxygen content increases from 2.90 to 3.05. W L3-edge x-ray absorption spectra further show that W-O bond intensity gradually weakens as oxygen content increases, indicative of more oxygen disorder present in the oxygen-rich samples. The observed results strongly suggest that the local lattice distortion induced by oxygen disorder not only modulates Rb vibration, possibly coupled to electron-phonon interaction responsible for superconductivity, and also reduces the charge transfer between O 2p and W 5d orbital in the vicinity of y =3.00. This scenario can possibly account for significant increases of Tc and normal-state resistivity of Rb0.23WOy as oxygen content slightly changes from 2.90 to 3.05.
- Published
- 2009
50. The Effect of Thermal Reduction on the Photoluminescence and Electronic Structures of Graphene Oxides.
- Author
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C.-H. Chuang, Y.-F. Wang, Y.-C. Shao, Y.-C. Yeh, D.-Y. Wang, C.-W. Chen, J. W. Chiou, Ray, Sekhar C., W. F. Pong, L. Zhang, J. F. Zhu, and J. H. Guo
- Subjects
PHOTOLUMINESCENCE ,GRAPHENE oxide ,FLUORESCENCE ,ELECTRONIC structure ,LOW temperatures ,X-ray absorption spectra ,FUNCTIONAL groups - Abstract
Electronic structures of graphene oxide (GO) and hydro-thermally reduced graphene oxides (rGOs) processed at low temperatures (120-180 °C) were studied using X-ray absorption near-edge structure (XANES), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS). C K-edge XANES spectra of rGOs reveal that thermal reduction restores C = C sp
2 bonds and removes some of the oxygen and hydroxyl groups of GO, which initiates the evolution of carbonaceous species. The combination of C K-edge XANES and Kα XES spectra shows that the overlapping π and π× orbitals in rGOs and GO are similar to that of highly ordered pyrolytic graphite (HOPG), which has no band-gap. C Kα RIXS spectra provide evidence that thermal reduction changes the density of states (DOSs) that is generated in the p-region and/or in the gap between the π and π× levels of the GO and rGOs. Two-dimensional C Kα RIXS mapping of the heavy reduction of rGOs further confirms that the residual oxygen and/or oxygen-containing functional groups modify the π and σ features, which are dispersed by the photon excitation energy. The dispersion behavior near the K point is approximately linear and differs from the parabolic-like dispersion observed in HOPG. [ABSTRACT FROM AUTHOR]- Published
- 2014
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