Publications (33)46.94 Total impact
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Article: Structural, optical, and magnetic characterization of Co and N co-doped ZnO nanopowders
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ABSTRACT: Co and N co-doped ZnO nanopowders with Co and N concentration 4, 6, and 8 mol% were synthesized by sol–gel method. Powder X-ray diffraction reveals that Co and N co-doped ZnO crystallize in wurtzite structure having space group C6v. Photo-luminescence studies show the reduction in band gap with increase in concentration of dopants. Micro Raman studies show the red shift for 1LO phonon peak with increase in doping, generally credited to the stress caused by lattice mismatch due to N doping in ZnO. X-ray absorption spectroscopy reveals that Co replaces the Zn atoms and N replace the O atoms in the host ZnO lattice. Magnetic studies show that Co and N codoped ZnO nanopowders exhibit ferromagnetic character at room temperature.Journal of Materials Science 12/2013; 48:2618-2623. · 2.02 Impact Factor -
Article: Room temperature ferromagnetism in Ni doped ZnS nanoparticles
Journal of Alloys and Compounds 12/2013; 554:357-362. · 2.29 Impact Factor -
Article: Electronic and atomic structures of gasochromic V2O5 films
EPL (Europhysics Letters) 01/2013; · 2.17 Impact Factor -
Article: Characterization of gasochromic Vanadium oxides films by x-ray absorption spectroscopy
Thin Solid Films 01/2013; · 1.89 Impact Factor -
Article: Anisotropic dissolution behavior of second phase in SnCu solder alloys under current stressing
Scripta Materialia 01/2013; 68:317-320. · 2.70 Impact Factor -
Article: Electronic and atomic structures of gasochromic V2O5 film
EPL (Europhysics Letters) 01/2013; 101:17006-p1~17006-p6. · 2.17 Impact Factor -
Article: Effect of Oxygen Partial Pressure on Structural and gaschromic properties of sputtered VOx thin films
Thin Solid Films 01/2013; · 1.89 Impact Factor -
Article: X-ray absorption spectroscopy studies of Ca2.9Ln0.1Co4O9+�delta (Ln = Ca, Dy, Ho, Erand Lu)
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ABSTRACT: Journal of Alloys and Compounds j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j a l l c o m X-ray absorption spectroscopy studies of Ca 2.9 Ln 0. a b s t r a c t X-ray absorption near edge structure (XANES) study of Co K-, Co L 2,3 -, O K-, and Ca L 2,3 -edges on a series of polycrystalline Ca 2.9 Ln 0.1 Co 4 O 9+ı (Ln = Ca, Dy, Ho, Er and Lu) are presented. The high similarity of Co K-edge spectra of the doped and the undoped samples indicate that the average valence of Co is slightly higher than 3+ and it is not varied for different dopants. The variation of the intensity of the Co L 2,3 -edge indicates that the number of Co 3d unoccupied states and thermoelectric power shows an opposite trend. According to the O K-edge spectra, the electrical resistivity and Co 4+ 3d–O 2p hybridized unoccupied states also show an opposite trend, which is consistent with our results that a lesser amount of Co 4+ leads to a larger thermoelectric power. There is a monotonic decrease of Ca L 2,3 -edge intensity with decreasing ionic radius of the Ln element, which partially substituted for Ca. This could be attributed to a decrease of Ca 3d–O 2p hybridization with decreasing ionic radius of Ln.Journal of Alloys and Compounds 01/2012; 529:8-11. · 2.29 Impact Factor -
Article: Effect of Mn substitution on electronic structure of Ca9Y(PO4)7:Eu2+, Mn2+ phosphor determined by X-ray absorption spectroscopy
Chemical Physics Letters Volume 515, Issues 4–6, 27 October 2011, Pages 245–248. 10/2011; -
Article: Role of 3d electrons in the rapid suppression of superconductivity in the dilute V doped spinel superconductor LiTi2O4
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ABSTRACT: The microscopic effects of V doping in LiTi2O4 have been poorly understood. The present study employs x-ray absorption near-edge structure (XANES) and resonant inelastic soft-x-ray scattering (RIXS) spectroscopy to understand the change in the electronic structure due to dilute V doping in spinel LiTi2O4 and the possible origin for the rapid suppression of superconductivity in these compounds. Results from the XANES spectra at Ti L and K edges and Ti L-RIXS show that Ti exists in a mixed-valence state and, with V doping, the unoccupied states of Ti in the t2g band increase. The rapid suppression of superconductivity is associated with the change in Ti 3d electrons and Ti–O hybridization.Superconductor Science and Technology 09/2011; 24(11):115007. · 2.66 Impact Factor -
Article: X-Ray spectra and electronic correlations of FeSe(1-x)Te(x).
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ABSTRACT: Critical issues concerning emerging Fe-based superconductors include the degree of electron correlation and the origin of the superconductivity. X-Ray absorption spectra (XAS) and resonant inelastic X-ray scattering spectra (RIXS) of FeSe(1-x)Te(x) (x = 0-1) single crystals were obtained to study their electronic properties that relate to electron correlation and superconductivity. The linewidth of Fe L(2,3)-edges XAS of FeSe(1-x)Te(x) is narrower than that of Fe-pnictides, revealing the difference between their hybridization effects and localization character and those of other Fe-pnictides. While no significant differences exist between the Fe L-edge XAS and RIXS of FeSe(1-x)Te(x) and those of Fe-pnictides, Se K-edge and Te K-edge XAS exhibit substantial edge shift, suggesting that the superconductivity in an Fe-Se superconductor is strongly associated with the ligand states. A comparison of the Se K-edge and Te K-edge spectra reveals that the charge transfer may occur between Se and Te. Given the Coulomb interaction and the bandwidth, the spectral results indicate that FeSe(1-x)Te(x) is unlikely to be a weakly correlated system unlike the Fe-pnictides of the "1111" and "122" families. The spectral results further demonstrate that superconductivity in this class of Fe-based compounds is strongly associated with the ligand 4p hole state.Physical Chemistry Chemical Physics 09/2011; 13(34):15666-72. · 3.57 Impact Factor -
Article: X-Ray spectra and electronic correlations of FeSe1–xTex
Physical Chemistry Chemical Physics 07/2011; · 3.57 Impact Factor -
Article: Size effects on mixed valence CePd3
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ABSTRACT: To study the size effects on mixed-valence state of CePd3, nanoparticles of CePd3, sizes ranging from 5.2 to 9.5 nm, were prepared. The mixed valence increased from 3.3 to 3.5 as particle size reduced from bulk to 5.2 nm. This consequence was illustrated by the enhancements of valence fluctuations and 4f electron hybridization with conduction band through size reduction. Another interesting finding in the nanoparticles is that a certain fraction ~ 25% of the sample becomes trivalent which is evident from the increase of magnetic susceptibility at low temperatures.Journal of Physics Conference Series 02/2011; 273(1):012041. -
Article: A study of thermal decomposition of sputtered NiO films
EPL (Europhysics Letters) 01/2011; 96:37009-p1~37009-p6. · 2.17 Impact Factor -
Article: Influence of itinerancy on the magnetic properties of the single crystals of Sr2YRu1-xCuxO6 solid solutions
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ABSTRACT: X-ray absorption spectroscopy(XAS) Ru L-edge and O K-edge measurements on single crystals of Sr2YRu1-xCuxO6 (x=0.01-0.05) solid solutions show that Cu replaces Ru in the lattice which results in a lattice distortion and itinerant holes that increase with increasing x. Powder X-ray diffraction (XRD) measurements confirm the lattice distortion through changes in the lattice parameters. Magnetic measurements reveal an antiferromagnetic transition at 32 K in the crystals with x=0 and a diamagnetic transition at 32 K for x \geq 0.01indicative of superconductivity in the zero field cooled (ZFC) curves. The field cooled (FC) curves show a weak ferromagnetic character with x=0 and a ferromagnetic transition at 30 K and an antiferromagnetic transition at 23 K in the presence of Cu. The peak at 30 K in the ac susceptibility measurements indicates a spin-glass behavior. The low field part of the M-H curve for x=0.05 crystal indicates weak superconductivity. The shifting of the M-H curve on FC indicates spin-glass state. In conjunction with the XAS results the magnetic behavior is explained in terms of a spontaneous vortex state as a result of the non-freezing Ru5+ spins.11/2010; -
Article: X-ray absorption spectroscopy (XAS) investigation of the electronic structure of superconducting FeSex single crystals
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ABSTRACT: X-ray absorption spectroscopy (XAS) Fe K-edge spectra of the FeSex (x=1-0.8) single crystals cleaved in situ in vacuum reveal characteristic Fe 4sp states, a lattice distortion and the Se K-edge spectra point to a strong Fe 3d-Se 4p hybridization giving rise to itinerant charge carriers. A formal charge of ~1.8+ for Fe and ~2.2- for Se were evaluated from these spectra in the FeSex (x=0.88). The charge balance between Fe and Se is assigned itinerant electrons located in the Fe-Se hybridization bond. As x decreases the 4p hole count increases and a crystal structure distortion is observed that in turn causes the Fe separation in the ab plane change from 4p orbital to varying (modulating) coordination. Powder x-ray diffraction (XRD) measurements also show a slight increase in lattice parameters as x decreases (increasing Se deficiency).05/2010; -
Article: Effect of Mn doping on the physical properties of misfit-layered Ca3Co4O9+δ
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ABSTRACT: We have carried out an x-ray absorption near-edge structure (XANES) study on a series of misfit-layered cobaltites Ca3Co4−xMnxO9+δ (x = 0, 0.05, 0.1, 0.15). In this system, the average valences of Co and Mn, according to Co and Mn K-edge measurements are about 3.50+ and 3+, respectively. Both the trivalent and tetravalent Co are of low-spin configurations as confirmed by our magnetization measurements. The variations of absorption intensities of Co L2,3-edge and O K-edge XANES with respect to the Mn doping concentration (x) are analysed. Co L2,3-edge results show that the Co 3d unoccupied states decrease with x, which correlate well with the trend of variation of thermoelectric power. O K-edge results indicate that the number of O 2p unoccupied states decreases with x, which implies a decrease in the majority charge carriers (hole) concentration upon partial substitution of Mn for Co.Journal of Physics D Applied Physics 06/2009; 42(13):135418. · 2.54 Impact Factor -
Article: Effect of surface treatments on the electronic properties of ultra-nanocrystalline diamond films
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ABSTRACT: We present the soft x-ray spectroscopic study of the ultra-nanocrystalline diamond (UNCD) films with different surface treatments. The samples were prepared by means of microwave plasma enhanced chemical vapor deposition (MPECVD) and the different surface treatments are applied to alter their field emission properties. The electronic properties were subsequently examined by the soft x-ray absorption and x-ray emission spectroscopy at carbon 1s threshold. From the experimental results, there is no significant variation in electronic structure of oxygen-and hydrogen-plasma treated UNCD films. On the other hand, the biased treated UNCD film shows more remarkable change on the sp 2 and sp 3 states. The formation of sp 2 bonding and the reduction of sp 3 bonding are the consequence of the improved electron field emission properties.01/2008; -
Article: X-ray spectroscopic study of the charge state and local ordering of room-temperature ferromagnetic Mn-doped ZnO.
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ABSTRACT: The charge state and local ordering of Mn doped into a pulsed laser deposited single-phase thin film of ZnO are investigated by using x-ray absorption spectroscopy at the O K-edge, Mn K-edge and L-edge, and x-ray emission spectroscopy at the O K-edge and Mn L-edge. This film is ferromagnetic at room temperature. EXAFS measurement shows that Mn(2+) replaces the Zn site in tetrahedral symmetry, and there is no evidence for either metallic Mn or MnO in the film. Upon Mn doping, the top of O 2p valence band extends into the bandgap, indicating additional charge carriers being created.Journal of Physics Condensed Matter 04/2007; 19(17):172202. · 2.55 Impact Factor -
Article: X-ray absorption and emission spectroscopy of ZnO nanoparticle and highly oriented ZnO microrod arrays
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ABSTRACT: The electronic structures of ZnO nanoparticles and microrod arrays are studied by O 1s X-ray absorption spectroscopy (XAS) and O Kα X-ray emission spectroscopy (XES). We show that the present LDA+USIC calculation approach is suitable to correct the LDA self-interaction error of the cation d-states. The atomic eigenstates of 3d in zinc and 2p in oxygen are energetically close, which induces strong Zn-3d-O-2p hybridization. This anomalous valence band cation-d-anion-p hybridization is affected when the localization of the Zn 3d-states is taken into account. Experimentally, the XES spectra show energy dependence in the spectral shape revealing selected excitations to the Zn 3d, 4s and 4p states, hybridized with O 2p states. Strong anisotropic effects are observed for the highly oriented ZnO rods, but not for the isotropic spherical nanoparticles. The nanostructured ZnO has primarily bulk XAS and XES properties.Microelectronics Journal. 01/2006;
Top co-authors
Top Journals
Institutions
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2011
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Academia Sinica
- Institute of Physics
Taipei, Taipei, Taiwan
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2010–2011
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National Synchrotron Radiation Research Center (NSRRC)
Hsinchu, Taiwan, Taiwan
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2005–2009
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Tamkang University
- Department of Physics
Taipei, Taipei, Taiwan -
Lawrence Berkeley National Laboratory
- Advanced Light Source Facility
Berkeley, CA, USA
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2008
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National Taiwan Normal University
Taipei, Taipei, Taiwan
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