Single-crystalline Ga-doped SnO2 nanowires and SnO2：Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder d...Single-crystalline Ga-doped SnO2 nanowires and SnO2：Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder diffraction （XRD）, field-emission scanning electron microscopy （FE-SEM）, energy-dispersive X-ray spectroscopy （EDS）, transmission electron microscopy （TEM） and selected-area electron diffraction （SAED）. FE-SEM images showed that the products consisted of nanowires and mierocombs that represent a novel morphology. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnO2. The influence of experimental conditions on the morphologies of the products is discussed. The morphology of the product showed a ribbon-like stem and nanoribbon array aligned evenly along one or both side of the nanoribbon. It was found that many Ga2O3 nanoparticles deposited on the surface of the microcombs. The major core nanoribbon grew mainly along the [110] direction and the self-organized branching nanoribbons grew epitaxially along [110] or [110] orientation from the （110） plane of the stem. A growth process was proposed for interpreting the growth of these remarkable SnO2：Ga2O3 heterogeneous microcombs. Due to the heavy doping of Ga, the emission peak in photoluminescence spectra has red-shifted as well as broadened significantly.展开更多
Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by...Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by Jones-Launder was employed. The numerical results were compared with the experimental data in the literature. It is found that the calculated results are in good agreement with the experimental data.展开更多
The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pe...The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.展开更多
In this work, under pressure 5.4 GPa and temperature 1250-1400°C, large gem-diamond single crystals with perfect shape and different content of additive boron were synthesized using temperature gradient method. H...In this work, under pressure 5.4 GPa and temperature 1250-1400°C, large gem-diamond single crystals with perfect shape and different content of additive boron were synthesized using temperature gradient method. High-purity boron powders were added as boron source into the graphite powder, and the effects of additive boron on crystal growth habit were investigated in detail. The relationship between the growth rate and the amount of additive boron was studied. The scanning electron microscopy was employed to study the morphology of boron-doped diamond crystals. Raman spectroscopy and Hall measurements were used to investigate the crystal structures and the carrier concentration, respectively. The results show that with the increase of the content of boron added into graphite powder, the crystal growth rate and the carrier concentration increase firstly, and decrease afterwards, and the zone-center phonon line at 1332 cm 1 has small shift to lower energy. The defects occur on the crystal surface when excessive boron is added in the synthesis system.展开更多
Lithium lutetium fluoride(LiLuF4) single crystals doped with different Dy3+ ion concentrations were grown by Bridgman method. The Judd-Ofelt(J-O) strength parameters(Ω2, Ω4, Ω6) of Dy3+ in LiLuF4 crystal are calcul...Lithium lutetium fluoride(LiLuF4) single crystals doped with different Dy3+ ion concentrations were grown by Bridgman method. The Judd-Ofelt(J-O) strength parameters(Ω2, Ω4, Ω6) of Dy3+ in LiLuF4 crystal are calculated according to the measured absorption spectra and the J-O theory, by which the asymmetry of the Dy3+:LiLuF4 single crystal and the possibility of attaining stimulated emission from 4F9/2 level are analyzed. The capability of the Dy3+:LiLuF4 crystal in generating white light by simultaneous blue and yellow emissions under excitation with ultraviolet light is produced. The effects of excitation wavelength and doping concentration on chromaticity coordinates and photoluminescence intensity are also investigated. Favorable CIE coordinates, x=0.319 3 and y=0.349 3, can be obtained for Dy3+ ion in 2.701% molar doping concentration under excitation of 350 nm.展开更多
Well-aligned single-crystal nanowire arrays of CH3NH3PbIs have shown potentials in laser sources and photovoltaic applications.Here we developed a solution based epitaxial method to grow CH3NH3PbI3nanowire arrays.By c...Well-aligned single-crystal nanowire arrays of CH3NH3PbIs have shown potentials in laser sources and photovoltaic applications.Here we developed a solution based epitaxial method to grow CH3NH3PbI3nanowire arrays.By confining the precursor solution between a silicon wafer and ST-cut quartz,the evaporation rate of the solvent was slowed down which brings a more stable and controllable solution environment.Relying on the lattice match between CH3NH3PbI3 and ST-cut quartz,arrays of single-crystal nanowires of CH3NH3PbI3have been grown epitaxially.The densities and lengths of CH3NH3PbI3 nanowires can be tuned. The lengths of the resultant crystals range from several microns to over one millimeter.Such CH3NH3PbI3arrays with good alignment and crystallinity were then applied to fabricate photovoltaic devices with good performances.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.20671027）, and the Natural Science Foundation of Anhui province, China （No.050440904）.
文摘Single-crystalline Ga-doped SnO2 nanowires and SnO2：Ga2O3 heterogeneous microcombs were synthesized by a simple one-step thermal evaporation and condensation method. They were characterized by means of X-ray powder diffraction （XRD）, field-emission scanning electron microscopy （FE-SEM）, energy-dispersive X-ray spectroscopy （EDS）, transmission electron microscopy （TEM） and selected-area electron diffraction （SAED）. FE-SEM images showed that the products consisted of nanowires and mierocombs that represent a novel morphology. XRD, SAED and EDS indicated that they were single-crystalline tetragonal SnO2. The influence of experimental conditions on the morphologies of the products is discussed. The morphology of the product showed a ribbon-like stem and nanoribbon array aligned evenly along one or both side of the nanoribbon. It was found that many Ga2O3 nanoparticles deposited on the surface of the microcombs. The major core nanoribbon grew mainly along the [110] direction and the self-organized branching nanoribbons grew epitaxially along [110] or [110] orientation from the （110） plane of the stem. A growth process was proposed for interpreting the growth of these remarkable SnO2：Ga2O3 heterogeneous microcombs. Due to the heavy doping of Ga, the emission peak in photoluminescence spectra has red-shifted as well as broadened significantly.
基金Supported by the Ph.D. Start-up Fund of Beijing University of Technology (No.127-00227).
文摘Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by Jones-Launder was employed. The numerical results were compared with the experimental data in the literature. It is found that the calculated results are in good agreement with the experimental data.
文摘The process of cold seeding melt growth of GdBa2Cu3Oy （Gd123） bulk superconductors using NdBa2Cu3Oy （Nd123） thin films was reported. In addition, a novel cold seeding concept of combining MgO crystal and buffer pellet was also introduced. The misorientation caused by the lattice mismatch between MgO and Gd123 melt was overcome by choosing suitable heat treatment program and Gd2BaCuO5 （Gd211） content of the buffer pellet. The doping effect of soft ferromagnetic NiFe alloy particles was also reported. The bulk sample with 0.4% （mole fraction） doping amount shows the best performance on the flux trapping. The critical current density is largely enhanced under the external field of 1-2 T, which is promising for large-scale applications. This effect is originated from the substitution of Fe and Ni ions for the Cu sites contributing to magnetic flux pinning.
文摘In this work, under pressure 5.4 GPa and temperature 1250-1400°C, large gem-diamond single crystals with perfect shape and different content of additive boron were synthesized using temperature gradient method. High-purity boron powders were added as boron source into the graphite powder, and the effects of additive boron on crystal growth habit were investigated in detail. The relationship between the growth rate and the amount of additive boron was studied. The scanning electron microscopy was employed to study the morphology of boron-doped diamond crystals. Raman spectroscopy and Hall measurements were used to investigate the crystal structures and the carrier concentration, respectively. The results show that with the increase of the content of boron added into graphite powder, the crystal growth rate and the carrier concentration increase firstly, and decrease afterwards, and the zone-center phonon line at 1332 cm 1 has small shift to lower energy. The defects occur on the crystal surface when excessive boron is added in the synthesis system.
基金supported by the National Natural Science Foundation of China(Nos.51272109 and 11374044)the Natural Science Foundation of Ningbo city(No.201401A6105016)K.C.Wong Magna Fund in Ningbo University
文摘Lithium lutetium fluoride(LiLuF4) single crystals doped with different Dy3+ ion concentrations were grown by Bridgman method. The Judd-Ofelt(J-O) strength parameters(Ω2, Ω4, Ω6) of Dy3+ in LiLuF4 crystal are calculated according to the measured absorption spectra and the J-O theory, by which the asymmetry of the Dy3+:LiLuF4 single crystal and the possibility of attaining stimulated emission from 4F9/2 level are analyzed. The capability of the Dy3+:LiLuF4 crystal in generating white light by simultaneous blue and yellow emissions under excitation with ultraviolet light is produced. The effects of excitation wavelength and doping concentration on chromaticity coordinates and photoluminescence intensity are also investigated. Favorable CIE coordinates, x=0.319 3 and y=0.349 3, can be obtained for Dy3+ ion in 2.701% molar doping concentration under excitation of 350 nm.
基金supported by the National Natural Science Foundation of China (21631002, U1632119, 21621061, and 91633301) Ministry of Science and Technology of the People’s Republic of China (2016YFA0201904)
文摘Well-aligned single-crystal nanowire arrays of CH3NH3PbIs have shown potentials in laser sources and photovoltaic applications.Here we developed a solution based epitaxial method to grow CH3NH3PbI3nanowire arrays.By confining the precursor solution between a silicon wafer and ST-cut quartz,the evaporation rate of the solvent was slowed down which brings a more stable and controllable solution environment.Relying on the lattice match between CH3NH3PbI3 and ST-cut quartz,arrays of single-crystal nanowires of CH3NH3PbI3have been grown epitaxially.The densities and lengths of CH3NH3PbI3 nanowires can be tuned. The lengths of the resultant crystals range from several microns to over one millimeter.Such CH3NH3PbI3arrays with good alignment and crystallinity were then applied to fabricate photovoltaic devices with good performances.
