The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Baojiu Chen - One of the best experts on this subject based on the ideXlab platform.

  • highly efficient up conversion luminescence in er 3 yb 3 co doped na 5 lu 9 f 32 single crystals by vertical Bridgman Method
    Scientific Reports, 2017
    Co-Authors: Haiping Xia, Jianli Zhang, Yongsheng Zhu, Baojiu Chen
    Abstract:

    Er3+/Yb3+ co-doped Na5Lu9F32 single crystals with different concentrations of Yb3+ ions were prepared to investigate their phase structure, up-conversion (UC) properties and mechanism of UC luminescence by Bridgman Method. Under 980 nm near-infrared (NIR) excitation, three sharp UC emission bands topping at green ~525 nm, ~548 nm and red ~669 nm were obtained in Er3+/Yb3+ doped Na5Lu9F32 single crystals which are attributing to the transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively. The quadratic dependence of pump power on UC emission indicated that two-photon process is in charge of the transition from excited state of Yb3+ ions to lower state of Er3+ ion in Na5Lu9F32 single crystals. The long-accepted mechanism for the production of red and green emissions through up-conversion (UC) under 980 nm excitation in Er3+/Yb3+ co-doped materials apply in the Na5Lu9F32 host was displayed. The enhancement of the red emission was observed due to a cross-relaxation (CR) process of the form: 4F7/2 + 4I11/2 → 4F9/2 + 4F9/2. Furthermore, an ideal yellowish green light performance could be achieved with 1.0 mol% Er3+ doped certain Yb3+ concentrations samples, and its external quantum efficiency approached to 6.80% under 5.5 Wcm−2 980 nm excitation which can be applied in developing UC displays for electro-optical devices.

  • infrared luminescent properties of na5lu9f32 single crystals co doped er3 yb3 grown by Bridgman Method
    Journal of Alloys and Compounds, 2016
    Co-Authors: Cheng Wang, Haiping Xia, Yuepin Zhang, Baojiu Chen, Zhigang Feng, Zhixiong Zhang, Dongsheng Jiang, Haochuan Jiang
    Abstract:

    Abstract Na 5 Lu 9 F 32 single crystals co-doped with various Er 3+ /Yb 3+ concentrations were grown by an improved Bridgman Method for the first time. The crystal structure is characterized by means of X-ray diffraction (XRD). High transmission in the range from 400 nm to 7150 nm and maximum phonon energy about 441 cm −1 for the Na 5 Lu 9 F 32 single crystals are obtained from the measured transmission and Raman spectra, respectively. The Judd-Ofelt parameters of Er 3+ in the obtained crystal was calculated and discussed according to the measured absorption spectra. Compared with the Er 3+ single-doped Na 5 Lu 9 F 32 crystal, an obviously enhanced emission band at 1500 nm was observed upon excitation of 980 nm laser diode (LD) via energy transfer from Yb 3+ to Er 3+ . Decay curve fitting using a Inokuti-Hirayama expression indicates dipole-dipole energy transfer from Yb 3+ to Er 3+ .The maximum emission cross section at ∼1.5 μm was also calculated to be 10.12 × 10 −20  cm 2 for the Na 5 Lu 9 F 32 single crystal of 1% Er 3+ and 6% Yb 3+ in molar fraction doping concentration.

  • fluorescence spectra of na 5 lu 9 f 32 single crystals co doped with ho 3 tm 3 grown by Bridgman Method
    Chemical Physics Letters, 2016
    Co-Authors: Zhigang Feng, Haiping Xia, Yuepin Zhang, Jian Zhang, Cheng Wang, Zhixiong Zhang, Dongsheng Jiang, Qingyang Tang, Qiguo Sheng, Baojiu Chen
    Abstract:

    Abstract This work presents the luminescent properties of Ho 3+ /Tm 3+ co-doped Na 5 Lu 9 F 32 single crystals that were grown by an improved Bridgman Method for the first time. The J–O intense parameters of Ho 3+ ions were calculated. An intense 2.0 μm emission was achieved with Tm 3+ ions sensitizing Ho 3+ ions by the processing of energy transfer from Tm 3+ ions to Ho 3+ ions under excitation of 800 nm LD. The maximum emission intensity at 2.0 μm is obtained, and the cross sections of Tm 3+ ions and Ho 3+ ions were calculated. The physical mechanism for energy transfer from Tm 3+ to Ho 3+ ions was analyzed by using Inokuti–Hirayama’s model.

  • efficient upconversion luminescence in er3 yb3 co doped cubic nayf4 single crystals by vertical Bridgman Method with kf flux
    Chinese Journal of Physics, 2016
    Co-Authors: Haiping Xia, Jianli Zhang, Haochuan Jiang, Cheng Wang, Zhigang Feng, Dongsheng Jiang, Qingyang Tang, Qiguo Sheng, Baojiu Chen
    Abstract:

    Abstract Er3+/Yb3+ co-doped α-NaYF4 single crystals with various Yb3+ concentrations and ∼0.50 mol% Er3+ were grown by Bridgman Method using Potassium fluoride as flux. The up-conversion (UC) luminescence and its pump power dependence on UC emission of the crystals under excitation of 980 nm laser diode were investigated. The UC emissions at green ∼522 nm, ∼541 nm and red ∼668 nm, which are attributed to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively, were obtained in Er3+/Yb3+ doped α-NaYF4 single crystals. The quadratic dependence of pump power on the UC emission suggests that a two-photon process is responsible for the transition from the excited Yb3+ to the lower state of Er3+ ions in α-NaYF4 single crystals. A favorable performance of yellowish green light can be achieved with certain Yb3+ concentrations and 0.52 mol% Er3+ co-doped samples that makes further research valuable in developing UC displays for electro-optical devices.

  • growth and downconversion luminescence of ho3 yb3 codoped α nayf4 single crystals by the Bridgman Method using a kf flux
    Crystal Research and Technology, 2015
    Co-Authors: Jiazhong Zhang, Haiping Xia, Jianli Zhang, Haochuan Jiang, Yongzhang Jiang, Shuo Yang, Baojiu Chen
    Abstract:

    Downconversion (DC) luminescence with emission at about 1000 nm under excitation of 448-nm light in Ho3+/Yb3+ codoped α-NaYF4 single crystal is realized. The crystal was grown by the Bridgman Method using KF as an assisting flux in a NaF-YF3 system. The energy-transfer process and quantum cutting (QC) mechanisms are presented through the analysis of the spectra. The energy-transfer processes of first- and second-order cooperative DC are responsible for the increase of the emission intensity at 1000 nm, and it is the first-order cooperative DC that is dominant for the DC process. When the Ho3+ concentration is fixed at about 0.8 mol%, the optimal concentration for ∼1000 nm emission is 3.02 mol% Yb3+ in the current research. The energy-transfer efficiency and the total quantum efficiency are analyzed through the luminescence decay curves. The maximum quantum cutting efficiency approaches to 184.4% in α-NaYF4 single crystals of 0.799 mol% Ho3+ and 15.15 mol% Yb3+. However, the emission intensity at 1000 nm decreases while the energy-transfer efficiency from Ho3+ to Yb3+ increases, which may result from the fluorescence quenching between Ho3+ and Yb3+ ions, Yb3+ and Yb3+ ions.

Tao Wang - One of the best experts on this subject based on the ideXlab platform.

  • growth of single crystal cd0 9zn0 1te ingots using pressure controlled Bridgman Method
    Crystals, 2020
    Co-Authors: Fan Yang, Wanqi Jie, Miao Wang, Xiaolong Sun, Ningbo Jia, Liying Yin, Boru Zhou, Tao Wang
    Abstract:

    We report growth of single-crystal Cd0.9Zn0.1Te ingots while using the pressure-controlled Bridgman Method. The Cd pressure was controlled during growth to suppress its evaporation from the melt and reduce the size of Te inclusions in the as-grown crystals. The accelerated crucible rotation technique (ACRT) was used to suppress constitutional supercooling. The fast accelerating and slow decelerating rotation speeds were optimized. Two-inch Cd0.9Zn0.1Te single-crystal ingots without grain boundaries or twins were grown reproducibly. Glow discharge mass spectrometry results indicate the effective segregation coefficients of Zn and In dopants are 1.24 and 0.18, respectively. The full width half maximum (FWHM) of X-ray rocking curve was approximately 22.5 ″, and the IR transmittance was approximately 61%, indicating high crystallinity. The mean size of the Te inclusions was approximately 13.4 μm. Single-crystal wafers were cut into 5 × 5 × 2 mm3 slices and then used to fabricate gamma ray detectors. The energy resolution and peak-to-valley ratio maps were constructed while using 59.5 keV gamma ray measurements, which proved the high uniformity of detection performance.

  • dislocations and te precipitates of cd0 9mn0 1te v crystal grown by tellurium solution vertical Bridgman Method
    Journal of Crystal Growth, 2019
    Co-Authors: Lijun Luan, Tao Wang, Wanqi Jie, Dan Zheng, Zongwen Liu, Hongwei Liu, Cuifeng Zhou, Li Duan
    Abstract:

    Abstract A successful growth of Cd0.9Mn0.1Te (CMT) ingot (vanadium doping concentration of 1 × 1017 atoms/cm3) was achieved by using the Tellurium (Te) solution vertical Bridgman Method. Using diffraction in the transmission electron microscope (TEM), the cell parameter of grown crystal was reckoned at 0.6496 nm. The [1 1  2 ¯ ] zone-axis diffraction pattern (DP) was obtained and indexed as the (1 1 1), the (1  3 ¯ 1 ¯ ), the (2  2 ¯  0) and the ( 3 ¯  1  1 ¯ ), respectively. Bright field (BF) image of the [1 1  2 ¯ ] zone-axis showed bend contours which caused by the lattice planes physically rotate and the lattice defects. A screw dislocation was assigned according to the changes characteristic of the bend contour when crossing the 1  3 ¯ 1 ¯ bend contour. And by imaging technique of high-resolution TEM (HRTEM), an edge dislocation and a set of stacking faults were recognized in the interfaces between Te precipitates and CMT: V. Then through the selected area diffraction (SAD) Method, an array of rod-shape monoclinic-phase Te precipitates was identified parallel to the [1  1 ¯  0] direction, i.e. the slip direction of the dislocation. The [1 0 0] zone-axis diffraction spots of the Te precipitates were superimposed on the [ 1 ¯  1 2] zone-axis of CMT: V. 020 spot of the Te precipitates was a double diffraction spot produced by interactions of the Te precipitates and CMT: V reflections. Moreover, the results indicated the moire fringes were formed in the area of misfitted and rotational lattices of the Te precipitates and CMT: V. They were interference interactions which magnified the differences of lattice spacing and relative orientation.

  • high quality gase single crystal grown by the Bridgman Method
    Materials, 2018
    Co-Authors: Tao Wang, Qinghua Zhao, Ziang Yin, Yinghan Zhang, Bingqi Chen, Yong Xie, Wanqi Jie
    Abstract:

    A high-quality GaSe single crystal was grown by the Bridgman Method. The X-ray rocking curve for the studied GaSe sample is symmetric and the Full Width at Half Maximum (FWHM) is only 46 arcs, which is the smallest value ever reported for GaSe crystals. The IR-transmittance is about 66% in the range from 500 to 4000 cm-1. The photoluminescence spectrum at 9.2 K shows a symmetric and sharp excition peak in 2.1046 eV. The results indicate that the as-grown GaSe crystal is of high crystalline quality. The as-grown e -GaSe crystal has a p-type conductance with the resistivity of 10³ Ω/cm, and the Hall mobility is ~25 cm² V-1 s-1. Few-layer GaSe crystals were prepared through mechanical exfoliation from this high-quality crystal sample. Few-layer GaSe-based photodetectors were fabricated, which exhibit an on/off ratio of 10⁴, a field-effect differential mobility of 0.4 cm² V-1 s-1, and have a fast response time less than 60 ms under light illumination.

  • Growth interface of In-doped CdMnTe from Te solution with vertical Bridgman Method under ACRT technique
    Transactions of Nonferrous Metals Society of China, 2012
    Co-Authors: Yuan-yuan Du, Xin Zheng, Tao Wang
    Abstract:

    Abstract CdMnTe (CMT) crystals were grown from Te solution with vertical Bridgman Method under accelerated crucible rotation (ACRT) technique. Ingot in diameter of 30 mm and length of 60 mm was obtained. The result shows that as-grown CMT has fewer twins compared with the one grown by conventional vertical Bridgman Method. However, IR microscopy shows that the microscopic growth interface morphology is non-uniform and irregular, which is attributed to higher Te inclusions density. Meanwhile, the laser confocal microscope images reveal that the Te phases are deposited randomly in the Te-rich CMT region with irregular shapes and voids. By optimizing the growth parameters to obtain a smooth interface, the Te solution vertical Bridgman technique can effectively reduce the twins in CMT crystal.

  • characterization of cdznte crystals grown using a seeded modified vertical Bridgman Method
    IEEE Transactions on Nuclear Science, 2009
    Co-Authors: Wanqi Jie, Tao Wang, P J Sellin, Gangqiang Zha, P Veeramani
    Abstract:

    In this paper, several 60 mm diameter CdZnTe crystal ingots, containing large-size single crystals, were grown using (111) or (211) orientation seeds by the modified vertical Bridgman Method. The Zn concentration distribution along the axial direction of the ingots was measured by near-infrared transmission spectroscopy at room temperature. The partition coefficient of Zn during the growth was calculated to be about 1.2. Zinc distribution uniformity measurements were carried out using photoluminescence mapping measurement at 80 K, which showed that the band gap variation in the CdZnTe wafers is less than 0.004 eV. IR microscopy showed that the diameters of the Te inclusions present in the material are in the range 6-9 mum, and the density of the inclusions is 1~3times105 cm-3. IR transmission measurements in the wave number region from 500 to 4000 cm-1 demonstrate that the IR transmittance of CdZnTe wafers is higher than 60%. Current-voltage measurements were performed on test structures fabricated using thermally evaporated Au contacts deposited on as-grown crystals, which revealed bulk resistivity values of 2~5times1010 Omegamiddotcm. Typical leakage currents for the planar devices were ~ 4 nA at a field strength of 1500 Vcm-1. The electron and hole mobility-lifetime products were evaluated using alpha particle irradiation. The obtained typical (mutau)e and (mutau)h values for the as-grown CdZnTe were 2.3times10-3 cm2V-1 and 1.5times10-4 cm2V-1, respectively.

Haiping Xia - One of the best experts on this subject based on the ideXlab platform.

  • highly efficient up conversion luminescence in er 3 yb 3 co doped na 5 lu 9 f 32 single crystals by vertical Bridgman Method
    Scientific Reports, 2017
    Co-Authors: Haiping Xia, Jianli Zhang, Yongsheng Zhu, Baojiu Chen
    Abstract:

    Er3+/Yb3+ co-doped Na5Lu9F32 single crystals with different concentrations of Yb3+ ions were prepared to investigate their phase structure, up-conversion (UC) properties and mechanism of UC luminescence by Bridgman Method. Under 980 nm near-infrared (NIR) excitation, three sharp UC emission bands topping at green ~525 nm, ~548 nm and red ~669 nm were obtained in Er3+/Yb3+ doped Na5Lu9F32 single crystals which are attributing to the transitions of 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively. The quadratic dependence of pump power on UC emission indicated that two-photon process is in charge of the transition from excited state of Yb3+ ions to lower state of Er3+ ion in Na5Lu9F32 single crystals. The long-accepted mechanism for the production of red and green emissions through up-conversion (UC) under 980 nm excitation in Er3+/Yb3+ co-doped materials apply in the Na5Lu9F32 host was displayed. The enhancement of the red emission was observed due to a cross-relaxation (CR) process of the form: 4F7/2 + 4I11/2 → 4F9/2 + 4F9/2. Furthermore, an ideal yellowish green light performance could be achieved with 1.0 mol% Er3+ doped certain Yb3+ concentrations samples, and its external quantum efficiency approached to 6.80% under 5.5 Wcm−2 980 nm excitation which can be applied in developing UC displays for electro-optical devices.

  • infrared luminescent properties of na5lu9f32 single crystals co doped er3 yb3 grown by Bridgman Method
    Journal of Alloys and Compounds, 2016
    Co-Authors: Cheng Wang, Haiping Xia, Yuepin Zhang, Baojiu Chen, Zhigang Feng, Zhixiong Zhang, Dongsheng Jiang, Haochuan Jiang
    Abstract:

    Abstract Na 5 Lu 9 F 32 single crystals co-doped with various Er 3+ /Yb 3+ concentrations were grown by an improved Bridgman Method for the first time. The crystal structure is characterized by means of X-ray diffraction (XRD). High transmission in the range from 400 nm to 7150 nm and maximum phonon energy about 441 cm −1 for the Na 5 Lu 9 F 32 single crystals are obtained from the measured transmission and Raman spectra, respectively. The Judd-Ofelt parameters of Er 3+ in the obtained crystal was calculated and discussed according to the measured absorption spectra. Compared with the Er 3+ single-doped Na 5 Lu 9 F 32 crystal, an obviously enhanced emission band at 1500 nm was observed upon excitation of 980 nm laser diode (LD) via energy transfer from Yb 3+ to Er 3+ . Decay curve fitting using a Inokuti-Hirayama expression indicates dipole-dipole energy transfer from Yb 3+ to Er 3+ .The maximum emission cross section at ∼1.5 μm was also calculated to be 10.12 × 10 −20  cm 2 for the Na 5 Lu 9 F 32 single crystal of 1% Er 3+ and 6% Yb 3+ in molar fraction doping concentration.

  • fluorescence spectra of na 5 lu 9 f 32 single crystals co doped with ho 3 tm 3 grown by Bridgman Method
    Chemical Physics Letters, 2016
    Co-Authors: Zhigang Feng, Haiping Xia, Yuepin Zhang, Jian Zhang, Cheng Wang, Zhixiong Zhang, Dongsheng Jiang, Qingyang Tang, Qiguo Sheng, Baojiu Chen
    Abstract:

    Abstract This work presents the luminescent properties of Ho 3+ /Tm 3+ co-doped Na 5 Lu 9 F 32 single crystals that were grown by an improved Bridgman Method for the first time. The J–O intense parameters of Ho 3+ ions were calculated. An intense 2.0 μm emission was achieved with Tm 3+ ions sensitizing Ho 3+ ions by the processing of energy transfer from Tm 3+ ions to Ho 3+ ions under excitation of 800 nm LD. The maximum emission intensity at 2.0 μm is obtained, and the cross sections of Tm 3+ ions and Ho 3+ ions were calculated. The physical mechanism for energy transfer from Tm 3+ to Ho 3+ ions was analyzed by using Inokuti–Hirayama’s model.

  • efficient upconversion luminescence in er3 yb3 co doped cubic nayf4 single crystals by vertical Bridgman Method with kf flux
    Chinese Journal of Physics, 2016
    Co-Authors: Haiping Xia, Jianli Zhang, Haochuan Jiang, Cheng Wang, Zhigang Feng, Dongsheng Jiang, Qingyang Tang, Qiguo Sheng, Baojiu Chen
    Abstract:

    Abstract Er3+/Yb3+ co-doped α-NaYF4 single crystals with various Yb3+ concentrations and ∼0.50 mol% Er3+ were grown by Bridgman Method using Potassium fluoride as flux. The up-conversion (UC) luminescence and its pump power dependence on UC emission of the crystals under excitation of 980 nm laser diode were investigated. The UC emissions at green ∼522 nm, ∼541 nm and red ∼668 nm, which are attributed to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively, were obtained in Er3+/Yb3+ doped α-NaYF4 single crystals. The quadratic dependence of pump power on the UC emission suggests that a two-photon process is responsible for the transition from the excited Yb3+ to the lower state of Er3+ ions in α-NaYF4 single crystals. A favorable performance of yellowish green light can be achieved with certain Yb3+ concentrations and 0.52 mol% Er3+ co-doped samples that makes further research valuable in developing UC displays for electro-optical devices.

  • growth and downconversion luminescence of ho3 yb3 codoped α nayf4 single crystals by the Bridgman Method using a kf flux
    Crystal Research and Technology, 2015
    Co-Authors: Jiazhong Zhang, Haiping Xia, Jianli Zhang, Haochuan Jiang, Yongzhang Jiang, Shuo Yang, Baojiu Chen
    Abstract:

    Downconversion (DC) luminescence with emission at about 1000 nm under excitation of 448-nm light in Ho3+/Yb3+ codoped α-NaYF4 single crystal is realized. The crystal was grown by the Bridgman Method using KF as an assisting flux in a NaF-YF3 system. The energy-transfer process and quantum cutting (QC) mechanisms are presented through the analysis of the spectra. The energy-transfer processes of first- and second-order cooperative DC are responsible for the increase of the emission intensity at 1000 nm, and it is the first-order cooperative DC that is dominant for the DC process. When the Ho3+ concentration is fixed at about 0.8 mol%, the optimal concentration for ∼1000 nm emission is 3.02 mol% Yb3+ in the current research. The energy-transfer efficiency and the total quantum efficiency are analyzed through the luminescence decay curves. The maximum quantum cutting efficiency approaches to 184.4% in α-NaYF4 single crystals of 0.799 mol% Ho3+ and 15.15 mol% Yb3+. However, the emission intensity at 1000 nm decreases while the energy-transfer efficiency from Ho3+ to Yb3+ increases, which may result from the fluorescence quenching between Ho3+ and Yb3+ ions, Yb3+ and Yb3+ ions.

Haochuan Jiang - One of the best experts on this subject based on the ideXlab platform.

  • single crystal growth of sn0 97ag0 03se by a novel horizontal Bridgman Method and its thermoelectric properties
    Journal of Crystal Growth, 2017
    Co-Authors: Min Jin, Haochuan Jiang, Hui Shen, Hezhu Shao, Guoqiang Liu, Jun Jiang
    Abstract:

    Abstract SnSe-based single crystal has attracted much attention due to its outstanding thermoelectric behaviors, however, the fabrication of large size crystal seems difficult as it is very easy to cleavage during crystal growth. In this work, a novel horizontal Bridgman Method was employed to produce SnSe crystal with 3 mol% Ag substitute for Sn. The Sn0.97Ag0.03Se raw material was in-situ synthesized in the horizontal Bridgman furnace and the crystal was grown in a PBN crucible. B2O3 encapsulant was used to prevent Se volatilization. The as-grown Sn0.97Ag0.03Se crystal was about 105 g in weight and a 25 mm×20 mm×15 mm single crystal was obtained. The density of the single crystal of 6.178 g/cm3 close to the theoretical value was measured. X-ray powder diffraction measurement indicated Sn0.97Ag0.03Se single crystal had orthorhombic Pnma structure at room temperature. The thermoelectric properties along a axis were analyzed and the Figure-of-merit, ZT=0.95 was obtained at 793 K mainly due to the low thermal conductivity near the Pnma-Cmcm phase transition temperature.

  • infrared luminescent properties of na5lu9f32 single crystals co doped er3 yb3 grown by Bridgman Method
    Journal of Alloys and Compounds, 2016
    Co-Authors: Cheng Wang, Haiping Xia, Yuepin Zhang, Baojiu Chen, Zhigang Feng, Zhixiong Zhang, Dongsheng Jiang, Haochuan Jiang
    Abstract:

    Abstract Na 5 Lu 9 F 32 single crystals co-doped with various Er 3+ /Yb 3+ concentrations were grown by an improved Bridgman Method for the first time. The crystal structure is characterized by means of X-ray diffraction (XRD). High transmission in the range from 400 nm to 7150 nm and maximum phonon energy about 441 cm −1 for the Na 5 Lu 9 F 32 single crystals are obtained from the measured transmission and Raman spectra, respectively. The Judd-Ofelt parameters of Er 3+ in the obtained crystal was calculated and discussed according to the measured absorption spectra. Compared with the Er 3+ single-doped Na 5 Lu 9 F 32 crystal, an obviously enhanced emission band at 1500 nm was observed upon excitation of 980 nm laser diode (LD) via energy transfer from Yb 3+ to Er 3+ . Decay curve fitting using a Inokuti-Hirayama expression indicates dipole-dipole energy transfer from Yb 3+ to Er 3+ .The maximum emission cross section at ∼1.5 μm was also calculated to be 10.12 × 10 −20  cm 2 for the Na 5 Lu 9 F 32 single crystal of 1% Er 3+ and 6% Yb 3+ in molar fraction doping concentration.

  • efficient upconversion luminescence in er3 yb3 co doped cubic nayf4 single crystals by vertical Bridgman Method with kf flux
    Chinese Journal of Physics, 2016
    Co-Authors: Haiping Xia, Jianli Zhang, Haochuan Jiang, Cheng Wang, Zhigang Feng, Dongsheng Jiang, Qingyang Tang, Qiguo Sheng, Baojiu Chen
    Abstract:

    Abstract Er3+/Yb3+ co-doped α-NaYF4 single crystals with various Yb3+ concentrations and ∼0.50 mol% Er3+ were grown by Bridgman Method using Potassium fluoride as flux. The up-conversion (UC) luminescence and its pump power dependence on UC emission of the crystals under excitation of 980 nm laser diode were investigated. The UC emissions at green ∼522 nm, ∼541 nm and red ∼668 nm, which are attributed to 2H11/2 → 4I15/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2, respectively, were obtained in Er3+/Yb3+ doped α-NaYF4 single crystals. The quadratic dependence of pump power on the UC emission suggests that a two-photon process is responsible for the transition from the excited Yb3+ to the lower state of Er3+ ions in α-NaYF4 single crystals. A favorable performance of yellowish green light can be achieved with certain Yb3+ concentrations and 0.52 mol% Er3+ co-doped samples that makes further research valuable in developing UC displays for electro-optical devices.

  • growth and downconversion luminescence of ho3 yb3 codoped α nayf4 single crystals by the Bridgman Method using a kf flux
    Crystal Research and Technology, 2015
    Co-Authors: Jiazhong Zhang, Haiping Xia, Jianli Zhang, Haochuan Jiang, Yongzhang Jiang, Shuo Yang, Baojiu Chen
    Abstract:

    Downconversion (DC) luminescence with emission at about 1000 nm under excitation of 448-nm light in Ho3+/Yb3+ codoped α-NaYF4 single crystal is realized. The crystal was grown by the Bridgman Method using KF as an assisting flux in a NaF-YF3 system. The energy-transfer process and quantum cutting (QC) mechanisms are presented through the analysis of the spectra. The energy-transfer processes of first- and second-order cooperative DC are responsible for the increase of the emission intensity at 1000 nm, and it is the first-order cooperative DC that is dominant for the DC process. When the Ho3+ concentration is fixed at about 0.8 mol%, the optimal concentration for ∼1000 nm emission is 3.02 mol% Yb3+ in the current research. The energy-transfer efficiency and the total quantum efficiency are analyzed through the luminescence decay curves. The maximum quantum cutting efficiency approaches to 184.4% in α-NaYF4 single crystals of 0.799 mol% Ho3+ and 15.15 mol% Yb3+. However, the emission intensity at 1000 nm decreases while the energy-transfer efficiency from Ho3+ to Yb3+ increases, which may result from the fluorescence quenching between Ho3+ and Yb3+ ions, Yb3+ and Yb3+ ions.

  • efficient quantum cutting in tb3 yb3 codoped alpha nayf4 single crystals grown by Bridgman Method using kf flux for solar photovoltaic
    IEEE Journal of Quantum Electronics, 2015
    Co-Authors: Jiazhong Zhang, Haiping Xia, Haochuan Jiang, Yongzhang Jiang, Shuo Yang, Baojiu Chen
    Abstract:

    Tb 3+ /Yb 3+ codoped α-NaYF 4 single crystals with various Yb 3+ concentrations and ~0.40 mol% Tb 3+ are grown by Bridgman Method using KF (Potassium fluoride) as flux with a temperature gradient of 70 °C/cm-90 °C/cm across the solid-liquid interface. The effect and mechanisms of KF in the growing process are studied. The crystal structure is characterized by means of XRD. The high transmission from 300 to 7350 nm and maximum phonon energy about 390 cm -1 for the α-NaYF 4 single crystal are obtained from the measured transmission and Raman spectra, respectively. The luminescent properties of the crystals are investigated through excitation, emission spectra, and decay curves. Downconversion with emission of two near-infrared photons about 1000 nm for each blue photon at 486-nm absorption is obtained in Tb 3+ /Yb 3+ codoped α-NaYF 4 single crystals. Moreover, the energy transfer processes is studied based on the Inokuti-Hirayama model from the measured luminescent decay curves, and the results indicated that the interaction between Tb 3+ and Yb 3+ is electric dipole-dipole. The maximum quantum cutting efficiency approached 174.6% in α-NaYF 4 single crystal with 0.42 mol% Tb 3+ and 9.98 mol% Yb 3+ , making it a potential candidate for applications in silicon-based solar cells.

Wanqi Jie - One of the best experts on this subject based on the ideXlab platform.

  • growth of single crystal cd0 9zn0 1te ingots using pressure controlled Bridgman Method
    Crystals, 2020
    Co-Authors: Fan Yang, Wanqi Jie, Miao Wang, Xiaolong Sun, Ningbo Jia, Liying Yin, Boru Zhou, Tao Wang
    Abstract:

    We report growth of single-crystal Cd0.9Zn0.1Te ingots while using the pressure-controlled Bridgman Method. The Cd pressure was controlled during growth to suppress its evaporation from the melt and reduce the size of Te inclusions in the as-grown crystals. The accelerated crucible rotation technique (ACRT) was used to suppress constitutional supercooling. The fast accelerating and slow decelerating rotation speeds were optimized. Two-inch Cd0.9Zn0.1Te single-crystal ingots without grain boundaries or twins were grown reproducibly. Glow discharge mass spectrometry results indicate the effective segregation coefficients of Zn and In dopants are 1.24 and 0.18, respectively. The full width half maximum (FWHM) of X-ray rocking curve was approximately 22.5 ″, and the IR transmittance was approximately 61%, indicating high crystallinity. The mean size of the Te inclusions was approximately 13.4 μm. Single-crystal wafers were cut into 5 × 5 × 2 mm3 slices and then used to fabricate gamma ray detectors. The energy resolution and peak-to-valley ratio maps were constructed while using 59.5 keV gamma ray measurements, which proved the high uniformity of detection performance.

  • dislocations and te precipitates of cd0 9mn0 1te v crystal grown by tellurium solution vertical Bridgman Method
    Journal of Crystal Growth, 2019
    Co-Authors: Lijun Luan, Tao Wang, Wanqi Jie, Dan Zheng, Zongwen Liu, Hongwei Liu, Cuifeng Zhou, Li Duan
    Abstract:

    Abstract A successful growth of Cd0.9Mn0.1Te (CMT) ingot (vanadium doping concentration of 1 × 1017 atoms/cm3) was achieved by using the Tellurium (Te) solution vertical Bridgman Method. Using diffraction in the transmission electron microscope (TEM), the cell parameter of grown crystal was reckoned at 0.6496 nm. The [1 1  2 ¯ ] zone-axis diffraction pattern (DP) was obtained and indexed as the (1 1 1), the (1  3 ¯ 1 ¯ ), the (2  2 ¯  0) and the ( 3 ¯  1  1 ¯ ), respectively. Bright field (BF) image of the [1 1  2 ¯ ] zone-axis showed bend contours which caused by the lattice planes physically rotate and the lattice defects. A screw dislocation was assigned according to the changes characteristic of the bend contour when crossing the 1  3 ¯ 1 ¯ bend contour. And by imaging technique of high-resolution TEM (HRTEM), an edge dislocation and a set of stacking faults were recognized in the interfaces between Te precipitates and CMT: V. Then through the selected area diffraction (SAD) Method, an array of rod-shape monoclinic-phase Te precipitates was identified parallel to the [1  1 ¯  0] direction, i.e. the slip direction of the dislocation. The [1 0 0] zone-axis diffraction spots of the Te precipitates were superimposed on the [ 1 ¯  1 2] zone-axis of CMT: V. 020 spot of the Te precipitates was a double diffraction spot produced by interactions of the Te precipitates and CMT: V reflections. Moreover, the results indicated the moire fringes were formed in the area of misfitted and rotational lattices of the Te precipitates and CMT: V. They were interference interactions which magnified the differences of lattice spacing and relative orientation.

  • high quality gase single crystal grown by the Bridgman Method
    Materials, 2018
    Co-Authors: Tao Wang, Qinghua Zhao, Ziang Yin, Yinghan Zhang, Bingqi Chen, Yong Xie, Wanqi Jie
    Abstract:

    A high-quality GaSe single crystal was grown by the Bridgman Method. The X-ray rocking curve for the studied GaSe sample is symmetric and the Full Width at Half Maximum (FWHM) is only 46 arcs, which is the smallest value ever reported for GaSe crystals. The IR-transmittance is about 66% in the range from 500 to 4000 cm-1. The photoluminescence spectrum at 9.2 K shows a symmetric and sharp excition peak in 2.1046 eV. The results indicate that the as-grown GaSe crystal is of high crystalline quality. The as-grown e -GaSe crystal has a p-type conductance with the resistivity of 10³ Ω/cm, and the Hall mobility is ~25 cm² V-1 s-1. Few-layer GaSe crystals were prepared through mechanical exfoliation from this high-quality crystal sample. Few-layer GaSe-based photodetectors were fabricated, which exhibit an on/off ratio of 10⁴, a field-effect differential mobility of 0.4 cm² V-1 s-1, and have a fast response time less than 60 ms under light illumination.

  • growth of znte single crystals from te solution by vertical Bridgman Method with acrt
    Journal of Crystal Growth, 2014
    Co-Authors: Rui Yang, Wanqi Jie, Hang Liu
    Abstract:

    Abstract ZnTe ingots 30 mm in diameter and about 60 mm in length were grown from Te solution based on vertical Bridgman Method with accelerated crucible rotation technique (ACRT). The composition homogeneity and the optical and electrical properties of the crystals were investigated using optical transmission microscope, energy dispersive spectrometer (EDS), scanning electron microscope (SEM), electron probe micro-analyzer (EPMA), ultraviolet–visible (UV–Vis) spectrophotometer, Fourier transform infrared (FT-IR) spectrometer and digital electrometer. The growth Method was found efficient for mass transfer, and produced large size single crystal with the volume up to 10 mm×10 mm×40 mm. Single crystals formed in the earlier stage of growth process are larger in size with less Te inclusions. Secondary inclusions formed due to thermal migration and crystal cracking were found. The IR transmittance over the wavenumber range from 500 to 4000 cm −1 is about 60%, and the band gap is about 2.23 eV at room temperature (RT). Its resistivity can reach up to about 700 Ω cm, which is the highest ever reported for unintentionally doped ZnTe crystal.

  • twins in cdmnte single crystals grown by Bridgman Method
    Crystal Research and Technology, 2010
    Co-Authors: Jijun Zhang, Wanqi Jie, Linjun Wang, Lijun Luan
    Abstract:

    Cd1-xMnxTe (x =0.2, CdMnTe) crystal was grown by the vertical Bridgman Method, which exhibits a pure zincblende structure in the whole ingot. The major defect, twins, which is fatal to CdMnTe crystal, was analyzed with scanning electron microscopy (SEM), X-ray energy disperse spectroscopy (XEDS) and optic microscopy on the chemical etching surface. The twins observed in the as-grown ingot are mainly lamellar ones, which lie on the {111} faces from the first-to-freeze region of the ingot and run parallel to the growth axis of the ingot. Coherent twins with {115}t-{111}h orientations when indexed with respect to both the twin and host orientations, are often found to be terminated by {110}t-{114}h lateral twins. Te inclusions with about 20 μm in width are observed to preferentially decorate the lamellar twin boundaries. The origin of the twins, relating to the growth twin and the phase transformation twin, is also discussed in this paper. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)