Browsing by Author "Ray, S. C."

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Determination of the microstructure of Eu-treated ZnO nanowires by x-ray absorption
(2010-02-08)
Huang, W. L.
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Labis, J.
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Ray, S. C.
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Liang, Y. R.
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Pao, C. W.
X-ray absorption near-edge structure (XANES), extended x-ray absorption fine structures (EXAFS), and photoluminescence measurements were used to elucidate the microstructural and photoluminescence properties of ZnO nanowires (ZnO-NWs) that had been treated with Eu by thermal diffusion. The O K- and Eu L(3)-edge XANES and EXAFS spectra at the Zn K- and Eu L(3)-edge verified the formation of Eu(2)O(3)-like layer on the surface of ZnO-NWs. X-ray diffraction, XANES and EXAFS measurements consistently suggest the lack of substitutional doping of Eu ions at the Zn ion sites in the interior of ZnO-NWs. The clear sharp and intense emission bands in the range 610-630 nm of Eu-treated ZnO-NWs originated from the intra-4f transition of Eu ions in the Eu(2)O(3)-like surface layer.
Local atomic and electronic structures and ferroelectric properties of PbZr(0.52)Ti(0.48)O(3): An x-ray absorption study (vol 99, 042909, 2011)
(2011-11-28)
Ray, S. C.
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Hsueh, H. C.
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Wu, C. H.
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Pao, C. W.
;
Asokan, K.
Local atomic and electronic structures and ferroelectric properties of PbZr0.52Ti0.48O3: An x-ray absorption study (vol 99, 042909, 2011)
(2011-11-28)
Ray, S. C.
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Hsueh, H. C.
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Wu, C. H.
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Pao, C. W.
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Asokan, K.
Loycal atomic and electronic structures and ferroelectric properties of PbZr(0.52)Ti(0.48)O(3): An x-ray absorption study
(2011-07-25)
Ray, S. C.
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Hsueh, H. C.
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Wu, C. H.
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Pao, C. W.
;
Asokan, K.
This work investigates local atomic and electronic structures of PbZr(0.52)Ti(0.48)O(3) (PZT) thin films with < 001 >, < 101 >, and < 111 > orientations using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy with theta = 0 degrees and 70 degrees incident angles. The EXAFS result indicates that the < 001 >-oriented PZT film has a polarization dominantly along the c-axis, while both < 101 >- and < 111 >-oriented PZT films have a dominant in-ab-plane polarization. The hysteresis-loop measurements show that the < 001 >-oriented PZT film has a much larger coercive field than those of other two PZT films, which indicates that the double-well potential along the c-axis is much deeper than that in the ab-plane. (C) 2011 American Institute of Physics. [doi:10.1063/1.3607475]
Loycal atomic and electronic structures and ferroelectric properties of PbZr0.52Ti0.48O3: An x-ray absorption study
(2011-07-25)
Ray, S. C.
;
Hsueh, H. C.
;
Wu, C. H.
;
Pao, C. W.
;
Asokan, K.
This work investigates local atomic and electronic structures of PbZr0.52Ti0.48O3 (PZT) thin films with < 001 >, < 101 >, and < 111 > orientations using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy with theta = 0 degrees and 70 degrees incident angles. The EXAFS result indicates that the < 001 >-oriented PZT film has a polarization dominantly along the c-axis, while both < 101 >- and < 111 >-oriented PZT films have a dominant in-ab-plane polarization. The hysteresis-loop measurements show that the < 001 >-oriented PZT film has a much larger coercive field than those of other two PZT films, which indicates that the double-well potential along the c-axis is much deeper than that in the ab-plane. (C) 2011 American Institute of Physics. [doi:10.1063/1.3607475]
Size dependence of the electronic structures and electron-phonon coupling in ZnO quantum dots
(2007-12-24)
Ray, S. C.
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Low, Y.
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Tsai, H. M.
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Pao, C. W.
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Chiou, J. W.
The electronic structures and optical properties of various sizes of ZnO quantum dots (QDs) were studied using x-ray absorption, photoluminescence, and Raman spectroscopy. The increase in the intensity ratio of the second-order Raman spectra of longitudinal optical mode and its fundamental mode, which is related to the strength of the electron-phonon coupling (EPC), is found to increase with the size of QD. The trend of EPC also correlates with the increase of the intensity ratio of the O 2p(pi) (I(pi)) and 2p(sigma) (I(sigma)) orbital features in the O K-edge x-ray absorption near-edge structure (XANES) as the size of QD increases. The EPC and XANES results suggest that the crystal orientations of ZnO QDs are approximately aligned with the c axis parallel with the polarization of x-ray photons. (c) 2007 American Institute of Physics.