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1

Hydrothermal Synthesis and Microstructural, Optical Properties Characterization of YVO_4 Phosphor Powder

100%

Zhang S., Liang Y., Gao X., Liu H.

Acta Physica Polonica A

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2014

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vol. 125

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issue 1

105-110

EN

The phonon energy of YVO_4 crystal is lower than other usual compounds of salt. So it is suitable as host material for down-conversion materials. Hydrothermal method was adopted to synthesize YVO_4 phosphor powder with the use of yttrium oxide and sodium vanadate as raw material. The change in the relative integral intensity of the (200) and (112) diffraction peaks indicates that macroscopic stress in the lattice obviously changes with the elevated hydrothermal reaction temperature. The YVO_4 phosphor powder synthesized involves a certain agglomeration of small particles. The phonon vibration in the YVO_4 originates mainly from the internal vibrations in the vanadium-oxygen tetrahedron, in addition to the Y-O and O-H vibrations. Due to a low phonon energy of only 2.8188 × 10^{-21} J, YVO_4 helps to improve the down-conversion efficiency of rare-earth ions. A bandgap value of approximately 3.8 eV for the synthesized YVO_4 powders leads to good absorption properties in the ultraviolet region. Upon excitation by the 320 nm ultraviolet photon, the intrinsic emission of YVO_4 powders is annihilated, and a broadband emission of VO_4^{3-} near 450 nm is observed at room temperature. The YVO_4 phosphor powder synthesized at 180C exhibits the maximum photoluminescence intensity because of its excellent crystallization.

2

Fabrication of High-Density GaN Nanowires through Ammoniating Ga_2O_3/Nb Films

76%

Zhuang H., Li B., Zhang S., Zhang X., Xue C., Wang D., Shen J.

Acta Physica Polonica A

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2008

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vol. 113

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issue 2

723-730

EN

High-density GaN nanowires were successfully synthesized on Si(111) substrates through ammoniating Ga_2O_3/Nb films under flowing ammonia atmosphere at 950°C. The as-synthesized GaN nanowires are characterized by X-ray diffraction, selected-area-electron diffraction, Fourier transform infrared, scanning electron microscopy, and field-emission transmission electron microscopy. The results show that the synthesized nanowires are single-crystal hexagonal wurtzite GaN with diameters ranging from 30 to 100 nm and lengths up to several microns. The photoluminescence spectra measured at room temperature only exhibit a strong and broad emission peak at 367.8 nm. Finally, the growth mechanism of GaN nanowires is discussed.

3

Growth of β-Ga_2O_3 Nanorods and Photoluminescence Properties

76%

Zhang, S., Zhuang H., Xue C., Li B., Shen J., Wang D.

Acta Physica Polonica A

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2007

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vol. 112

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issue 6

1195-1201

EN

β-Ga_2O_3 nanorods were successfully fabricated through annealing Ga_2O_3/Mo films deposited on the Si (111) substrate by radio frequency magnetron sputtering technique. The morphology and structure of the as-synthesized nanorods were characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-rays spectroscopy. The results show that the formed nanorods are single-crystalline Ga_2O_3 with monoclinic structure. The diameters of nanorods are 200 nm and lengths typically up to several micrometers. A photoluminescence spectrum at room temperature under excitation at 325 nm exhibits two strong blue-light peaks located at about 413.0 nm and 437.5 nm, attributed to the recombination of bound electron-hole exciton in β-Ga_2O_3 single crystal. The growth process of the β-Ga_2O_3 nanorods is probably dominated by conventional vapor-solid mechanism.

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Hydrothermal Synthesis and Microstructural, Optical Properties Characterization of YVO_4 Phosphor Powder

Fabrication of High-Density GaN Nanowires through Ammoniating Ga_2O_3/Nb Films

Growth of β-Ga_2O_3 Nanorods and Photoluminescence Properties