A facile and green strategy to synthesize orthorhombic black phosphorus(o-BP) single crystals with high yield(~90%) and large size(sub-3 millimeter) is presented. The strategy was based on a two-step heating chemical ...A facile and green strategy to synthesize orthorhombic black phosphorus(o-BP) single crystals with high yield(~90%) and large size(sub-3 millimeter) is presented. The strategy was based on a two-step heating chemical vapor transport(CVT) reaction method, in which tin and iodine(Sn/I2) was used as mineralization additives and red phosphorus as precursor. Tin phosphide was the only by-product captured at the end of reaction, which greatly simplified the subsequent separation and purification processes of o-BP single crystals. The full width at half maximum(FWHM) of X-ray rocking curve of the as-grown o-BP was 21.65 arc sec, indicating its respectable crystalline quality. A bottom electrode structure field-effect transistor(FET) based on the multilayer phosphorene mechanically exfoliated from the as-grown o-BP single crystal was successfully fabricated through an all-dry transfer technique. Impressively, the FET based on a 6 nm thick multilayer(approximate 12 layers) phosphorene exhibited a record high hole mobility(μp) of 1744 cm2 V-1 s-1 and an admirable on/off current switching ratio(Ion/Ioff) of ~104, which further proved the high-quality of the o-BP single crystals synthesized by the twostep heating CVT reaction method using the simple Sn/I2/red phosphorus system.展开更多
The development of efficient and stable electrocatalysts with earth-abundant elements for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)in the same electrolyte is incontrovertibly vital in wat...The development of efficient and stable electrocatalysts with earth-abundant elements for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)in the same electrolyte is incontrovertibly vital in water electrolysis.However,their large-scale fabrication remains a great challenge.Here,we report a self-supported electrocatalyst in the form of Fe-doped Ni_(3)S_(2) nanoparticles in-situ grown on three-dimensional(3D)conductive Fe−Ni alloy foam(Fe−Ni_(3)S_(2)/AF)by surface-assisted chemical vapor transport(SACVT)method.Homogeneous growth environment and scalability of SACVT method allow Fe−Ni3S2 nanoparticles uniformly growing on AF in large-scale.Fe−Ni_(3)S_(2)/AF exhibits high activity and durability when act as HER catalyst and OER precatalyst in alkaline media.The HER and OER overpotential at 10 mA/cm^(2) is considerably small,only 75 and 267 mV,respectively.Moreover,the electrolyzer assembled by Fe−Ni_(3)S_(2)/AF for overall water splitting exhibits a low cell voltage and high durability in long-term test.Based on experiments and theoretical calculation,the significantly enhanced activity could be originated from the incorporation of Fe,which contributed to increase the electrochemical active surface area,enhance electrical conductivity,optimize the hydrogen and H2O adsorption energy of Ni_(3)S_(2)(101)surface in HER,and form active bimetallic Ni−Fe(oxy)hydroxide in OER.The excellent durability of self-supported Fe−Ni_(3)S_(2)/AF could be benefited from the in-situ growth of Fe−Ni_(3)S_(2) nanoparticles on 3D AF,which could ensure closely mechanical adhesion between active materials and substrate,promote charge transport and increase surface area.This work provides a facile method for large-scale synthesis of electrocatalysts with high activity and long-term durability for efficient water electrolysis in alkaline media.展开更多
ZnO crystals were grown by CVT method in closed quartz tube under seeded condition. Carbon was used as a transport agent to enhance the chemical transport of ZnO in the growth process. ZnO single crystals were grown b...ZnO crystals were grown by CVT method in closed quartz tube under seeded condition. Carbon was used as a transport agent to enhance the chemical transport of ZnO in the growth process. ZnO single crystals were grown by using GaN/sapphire and GaN/Si wafer as seeds. The property and crystal quality of the ZnO single crystals was studied by photoluminescence spectroscopy and X-ray diffraction technique.展开更多
This paper introduces a feasible process to achieve the molybdenum disulfide atomic layers using chemical vapor deposition(CVD) method,with molybdenum thin film and solid sulfur as precursors.And some improvements wer...This paper introduces a feasible process to achieve the molybdenum disulfide atomic layers using chemical vapor deposition(CVD) method,with molybdenum thin film and solid sulfur as precursors.And some improvements were made to reduce the amount of metastable MoS_(2)-3 R.The morphology of the acquired MoS_(2) layers,existing as triangular flakes or large-area continuous films,can be controlled by adjusting the synthesis time and reacting temperature.The characterization results show that the monolayer MoS_(2) flakes reveal a(002)-oriented growth on SiO_(2)/Si substrates,and its crystalline domain size is approximately 30 μm,and the thickness is 0.65 nm.Since the synthesis of MoS_(2)-3 R is restrained,the electronic transport properties of MoS_(2) with different layers were investigated,revealing that those properties equal with those of MoS_(2) samples prepared by exfoliation methods.展开更多
We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport method.It...We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport method.It is found that the ferromagnetic MnSb_(2)Te_(4) changes to antiferromagnetism with Bi doping when x≥0.25.Further analysis implies that the occupations of Mn ions at Sb/Bi site Mn_(Sb/Bi) and Mn site Mn_(Mn) have a strong influence on the magnetic ground states of these systems.With the decrease of Mn_(Mn) increase of Mn_(Sb/Bi),the system will favor the ferromagnetic ground state.In addition,the rapid decrease of T_(C/N) with increasing Bi content when x ≤0.25 and the insensitivity of T_(N) to x when x> 0.25 suggest that the main magnetic interaction may change from the Ruderman-Kittel-Kasuya-Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples.展开更多
Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination chemical vapor transport reactions mediated by vapor complexes LnAl ...Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination chemical vapor transport reactions mediated by vapor complexes LnAl n Cl 3 n +3 (Ln=RE elements). The bastnaesite was heated to 800 K and chlorinated between 800～1300 K with C+Cl 2+SiCl 4 to remove CO 2, SiF 4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaCl 2 and BaCl 2 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.展开更多
Two-dimensional ZrS2 materials have potential for applications in nanoelectronics because of their theoretically predicted high mobility and sheet current density. Herein, we report the thickness and temperature depen...Two-dimensional ZrS2 materials have potential for applications in nanoelectronics because of their theoretically predicted high mobility and sheet current density. Herein, we report the thickness and temperature dependent transport properties of ZrS2 multilayers that were directly deposited on hexagonal boron nitride （h-BN） by chemical vapor deposition. Hysteresis-free gate sweeping, metal- insulator transition, and T-γ （γ- 0.82-1.26） temperature dependent mobility were observed in the ZrS2 films.展开更多
The mutual separation characteristics were investigated for the neighboring Sm, Eu and Gd from their ternary oxide mixture Sm 2O 3 Eu 2O 3 Gd 2O 3 by a stepwise chlorination chemical vapor transport reaction ...The mutual separation characteristics were investigated for the neighboring Sm, Eu and Gd from their ternary oxide mixture Sm 2O 3 Eu 2O 3 Gd 2O 3 by a stepwise chlorination chemical vapor transport reaction within 6 h using AlCl 3 as complex former. The rare earth chlorides were more readily transported and concentrated in the middle temperature range of 980～1100 K and the transport efficiency was in the order of Sm≈Gd>Eu. The separation factor, expressed as molar ratio for the resulting chlorides, was 1 70 for Eu∶Sm, 1 88 for Eu∶Gd, 1 24 for Sm∶Gd in the higher temperature region, and 2 76 for Sm∶Eu, 2 83 for Gd∶Eu and 1 12 for Gd∶Sm in the lower temperature region, respectively. All results are much higher than those of the conventional wet process.展开更多
Bulk single crystals β-FeSi2, as a new photoelectric and thermoelectric material, has been successfully grown using chemical vapor transport techniqueby using iodine as transport agent in a sealed ampoule. The effect...Bulk single crystals β-FeSi2, as a new photoelectric and thermoelectric material, has been successfully grown using chemical vapor transport techniqueby using iodine as transport agent in a sealed ampoule. The effects of crystal growth condition on quality and morphologies of the single crystals were studied. Both needle-like and grain-like single crystals were gained. By changing substrate temperature, tetrahedral high quality α-FeSi2 single crystals were also obtained.展开更多
Anhydrous lanthanide chlorides LnCl 3 (Ln=Sc, Y, La to Lu except for Pm), which are difficult to prepare in other ways, were prepared by chemical vapor transport (CVT) process. Rare earth oxide reacted with Al 2Cl ...Anhydrous lanthanide chlorides LnCl 3 (Ln=Sc, Y, La to Lu except for Pm), which are difficult to prepare in other ways, were prepared by chemical vapor transport (CVT) process. Rare earth oxide reacted with Al 2Cl 6 at 300℃ to produce LnCl 3, which was then separated from other solids by means of CVT at a temperature gradient from 400 to 180℃. Residual Al 2Cl 6 (g) was removed by carrier of dry N 2 gas at 200℃. The yielding rates were >90%, and the purity of products was >99.5%.展开更多
基金supported by the National Natural Science Foundation of China(5117309791333109+3 种基金61434001 and 61574083)the National Key Basic Research Program of China(2013CB632900)Tsinghua University Initiative Scientific Research Program(20131089202)the Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physics(KF201516)
文摘A facile and green strategy to synthesize orthorhombic black phosphorus(o-BP) single crystals with high yield(~90%) and large size(sub-3 millimeter) is presented. The strategy was based on a two-step heating chemical vapor transport(CVT) reaction method, in which tin and iodine(Sn/I2) was used as mineralization additives and red phosphorus as precursor. Tin phosphide was the only by-product captured at the end of reaction, which greatly simplified the subsequent separation and purification processes of o-BP single crystals. The full width at half maximum(FWHM) of X-ray rocking curve of the as-grown o-BP was 21.65 arc sec, indicating its respectable crystalline quality. A bottom electrode structure field-effect transistor(FET) based on the multilayer phosphorene mechanically exfoliated from the as-grown o-BP single crystal was successfully fabricated through an all-dry transfer technique. Impressively, the FET based on a 6 nm thick multilayer(approximate 12 layers) phosphorene exhibited a record high hole mobility(μp) of 1744 cm2 V-1 s-1 and an admirable on/off current switching ratio(Ion/Ioff) of ~104, which further proved the high-quality of the o-BP single crystals synthesized by the twostep heating CVT reaction method using the simple Sn/I2/red phosphorus system.
基金This work was supported by the National Key Research and Development Progra m of China(No.2017YFB1104300).
文摘The development of efficient and stable electrocatalysts with earth-abundant elements for both oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)in the same electrolyte is incontrovertibly vital in water electrolysis.However,their large-scale fabrication remains a great challenge.Here,we report a self-supported electrocatalyst in the form of Fe-doped Ni_(3)S_(2) nanoparticles in-situ grown on three-dimensional(3D)conductive Fe−Ni alloy foam(Fe−Ni_(3)S_(2)/AF)by surface-assisted chemical vapor transport(SACVT)method.Homogeneous growth environment and scalability of SACVT method allow Fe−Ni3S2 nanoparticles uniformly growing on AF in large-scale.Fe−Ni_(3)S_(2)/AF exhibits high activity and durability when act as HER catalyst and OER precatalyst in alkaline media.The HER and OER overpotential at 10 mA/cm^(2) is considerably small,only 75 and 267 mV,respectively.Moreover,the electrolyzer assembled by Fe−Ni_(3)S_(2)/AF for overall water splitting exhibits a low cell voltage and high durability in long-term test.Based on experiments and theoretical calculation,the significantly enhanced activity could be originated from the incorporation of Fe,which contributed to increase the electrochemical active surface area,enhance electrical conductivity,optimize the hydrogen and H2O adsorption energy of Ni_(3)S_(2)(101)surface in HER,and form active bimetallic Ni−Fe(oxy)hydroxide in OER.The excellent durability of self-supported Fe−Ni_(3)S_(2)/AF could be benefited from the in-situ growth of Fe−Ni_(3)S_(2) nanoparticles on 3D AF,which could ensure closely mechanical adhesion between active materials and substrate,promote charge transport and increase surface area.This work provides a facile method for large-scale synthesis of electrocatalysts with high activity and long-term durability for efficient water electrolysis in alkaline media.
文摘ZnO crystals were grown by CVT method in closed quartz tube under seeded condition. Carbon was used as a transport agent to enhance the chemical transport of ZnO in the growth process. ZnO single crystals were grown by using GaN/sapphire and GaN/Si wafer as seeds. The property and crystal quality of the ZnO single crystals was studied by photoluminescence spectroscopy and X-ray diffraction technique.
基金financially supported by the National Natural Science Foundation of China (Nos.50835002 and 51105102)。
文摘This paper introduces a feasible process to achieve the molybdenum disulfide atomic layers using chemical vapor deposition(CVD) method,with molybdenum thin film and solid sulfur as precursors.And some improvements were made to reduce the amount of metastable MoS_(2)-3 R.The morphology of the acquired MoS_(2) layers,existing as triangular flakes or large-area continuous films,can be controlled by adjusting the synthesis time and reacting temperature.The characterization results show that the monolayer MoS_(2) flakes reveal a(002)-oriented growth on SiO_(2)/Si substrates,and its crystalline domain size is approximately 30 μm,and the thickness is 0.65 nm.Since the synthesis of MoS_(2)-3 R is restrained,the electronic transport properties of MoS_(2) with different layers were investigated,revealing that those properties equal with those of MoS_(2) samples prepared by exfoliation methods.
基金Project supported by the Beijing Natural Science Foundation (Grant No. Z200005)the National Key R&D Program of China (Grant Nos. 2022YFA1403800 and 2023YFA1406500)+1 种基金the National Natural Science Foundation of China (Grant No. 12274459)Collaborative Research Project of Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology。
文摘We investigate the evolution of magnetic properties as well as the content and distribution of Mn for Mn(Sb_(1-x)Bi_(x))_(2)Te_(4) single crystals grown by large-temperature-gradient chemical vapor transport method.It is found that the ferromagnetic MnSb_(2)Te_(4) changes to antiferromagnetism with Bi doping when x≥0.25.Further analysis implies that the occupations of Mn ions at Sb/Bi site Mn_(Sb/Bi) and Mn site Mn_(Mn) have a strong influence on the magnetic ground states of these systems.With the decrease of Mn_(Mn) increase of Mn_(Sb/Bi),the system will favor the ferromagnetic ground state.In addition,the rapid decrease of T_(C/N) with increasing Bi content when x ≤0.25 and the insensitivity of T_(N) to x when x> 0.25 suggest that the main magnetic interaction may change from the Ruderman-Kittel-Kasuya-Yosida type at low Bi doping region to the van-Vleck type in high Bi doped samples.
文摘Vapor phase extraction and mutual separation of rare earth (RE) elements from bastnaesite concentrate were investigated using stepwise chlorination chemical vapor transport reactions mediated by vapor complexes LnAl n Cl 3 n +3 (Ln=RE elements). The bastnaesite was heated to 800 K and chlorinated between 800～1300 K with C+Cl 2+SiCl 4 to remove CO 2, SiF 4 and high volatile chlorides. At the temperature of 1300 K for 6 h, the resulted RE chlorides were chemically transported and mutual separated with the vapor complexes while CaCl 2 and BaCl 2 were remained in the residues. Significantly different CVT characteristics were observed for gradually decreased and wave form temperature gradients.
基金L. M. X. acknowledges support from National Natural Science Foundation of China （Nos. 21373066 and 11304052）, Beijing Nova programme （No. Z151100000315081） and Beijing Talents Fund （No. 2015000021223ZK17）. C. Z. C. acknowledges support from the Program for New Century Excellent Talents in University of China （No. NCET-07-0903）.
文摘Two-dimensional ZrS2 materials have potential for applications in nanoelectronics because of their theoretically predicted high mobility and sheet current density. Herein, we report the thickness and temperature dependent transport properties of ZrS2 multilayers that were directly deposited on hexagonal boron nitride （h-BN） by chemical vapor deposition. Hysteresis-free gate sweeping, metal- insulator transition, and T-γ （γ- 0.82-1.26） temperature dependent mobility were observed in the ZrS2 films.
文摘The mutual separation characteristics were investigated for the neighboring Sm, Eu and Gd from their ternary oxide mixture Sm 2O 3 Eu 2O 3 Gd 2O 3 by a stepwise chlorination chemical vapor transport reaction within 6 h using AlCl 3 as complex former. The rare earth chlorides were more readily transported and concentrated in the middle temperature range of 980～1100 K and the transport efficiency was in the order of Sm≈Gd>Eu. The separation factor, expressed as molar ratio for the resulting chlorides, was 1 70 for Eu∶Sm, 1 88 for Eu∶Gd, 1 24 for Sm∶Gd in the higher temperature region, and 2 76 for Sm∶Eu, 2 83 for Gd∶Eu and 1 12 for Gd∶Sm in the lower temperature region, respectively. All results are much higher than those of the conventional wet process.
基金the National Natural Science Foundation of China(Grant No.50171077)863 project
文摘Bulk single crystals β-FeSi2, as a new photoelectric and thermoelectric material, has been successfully grown using chemical vapor transport techniqueby using iodine as transport agent in a sealed ampoule. The effects of crystal growth condition on quality and morphologies of the single crystals were studied. Both needle-like and grain-like single crystals were gained. By changing substrate temperature, tetrahedral high quality α-FeSi2 single crystals were also obtained.
文摘Anhydrous lanthanide chlorides LnCl 3 (Ln=Sc, Y, La to Lu except for Pm), which are difficult to prepare in other ways, were prepared by chemical vapor transport (CVT) process. Rare earth oxide reacted with Al 2Cl 6 at 300℃ to produce LnCl 3, which was then separated from other solids by means of CVT at a temperature gradient from 400 to 180℃. Residual Al 2Cl 6 (g) was removed by carrier of dry N 2 gas at 200℃. The yielding rates were >90%, and the purity of products was >99.5%.
