On the basis of known structures of 13-GeTe bulk and the derived monolayer,we proposed a series of structural analogues MXs(M=Ge,Sn;X=S,Se,Te)with an intrinsic built-in electric field via a substitution strategy.Using...On the basis of known structures of 13-GeTe bulk and the derived monolayer,we proposed a series of structural analogues MXs(M=Ge,Sn;X=S,Se,Te)with an intrinsic built-in electric field via a substitution strategy.Using first-principles calculations,we demonstrated that these MX monolayers and bulks are thermodynamically,dynamically and mechanically stable,and the stabilities of bulks are more robust than the monolayer counterparts.Electronic calculations showed that the monolayers have large band gaps ranging from 2.38 to 3.27 eV while the bulks have pronounced small band gaps ranging from 0.06 to 0.78 eV.The calculated piezoelectric coefficients d11 for the MX monolayers are in the range from 6.6 to 10.9 pmN.Strikingly,the calculated d33 for the MX bulks are as high as 40.3-213.7 pm/V.By correlating atomic polarizability,atomic mass,relative ion motion,Bader charge and lattice parameters,we proposed an empirical model to estimate the piezoelectric coefficients for the two-dimensional:(2D)MXs,where a nice match between the estimated ones and the calculated ones was found.The versatile electronic propertiesand large piezoelectric coefficients endow MXs a broad prospect of application in optoelectronic and piezoelectric devices,and the revealed underlying mechanisms offer valuable guidelines for seeking novel piezoelectrics.展开更多
Three-dimensional(3D)topological insulators(TIs)have been studied for approximately fifteen years,but those made from group-IV elements,especially Ge and Sn,seem particularly attractive owing to their nontoxicity,siza...Three-dimensional(3D)topological insulators(TIs)have been studied for approximately fifteen years,but those made from group-IV elements,especially Ge and Sn,seem particularly attractive owing to their nontoxicity,sizable intrinsic spin–orbit coupling(SOC)strength and natural compatibility with the current semiconductor industry.However,group-IV elemental TIs have rarely been reported,except for the low temperature phase ofα-Sn under strain.Here,based on first-principles calculations,we propose new allotropes of Ge and Sn,named T5-Ge/Sn,as desirable TIs.These new allotropes are also highly anisotropic Dirac semimetals if the SOC is turned off.To the best of our knowledge,T5-Ge/Sn are the first 3D allotropes of Ge/Sn that possess topological states in their equilibrium states at room temperature.Additionally,their isostructures of C and Si are metastable indirect and direct semiconductors.Our work not only reveals two promising TIs,but more profoundly,we justify the advantages of group-IV elements as topological quantum materials(TQMs)for fundamental research and potential practical applications,and thus reveal a new direction in the search for desirable TQMs.展开更多
A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O-NS] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N = CHC6H2O）]- （La） and dianionic phenoxy-amine arylsulfide [O...A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O-NS] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N = CHC6H2O）]- （La） and dianionic phenoxy-amine arylsulfide [O-N-S] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N-CH2C6H2O）]2- （Lb） have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether. Half-sandwich Group Ⅳ metal complexes CpTi[O-NS]Cl2 （1a）, CpZr[O-NS]Cl2 （1b）, CpTi[O-N-S]Cl （2a）, CpZr[O-N-S]Cl （2b） and CpZr[O-N-S]Cl （2c） were synthesized by the reactions of La and Lb with CpTiCl3, CpZrCl3 and Cp ZrCl3, and characterized by IR, ^1H-NMR, ^13C-NMR and elemental analysis. In addition, an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane （MAO） as co-catalyst up to 1.58 × 10^7 g-PE.mol-Zr-1.h-1. The good catalytic activities can be maintained even at high temperatures such as 100 ℃ exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.展开更多
As an important member of the two-dimensional layers of metal dichalcogenides family, the two-dimensional(2 D)group IV metal chalcogenides(GIVMCs) have been attracting intensive attention. However, the growth of monol...As an important member of the two-dimensional layers of metal dichalcogenides family, the two-dimensional(2 D)group IV metal chalcogenides(GIVMCs) have been attracting intensive attention. However, the growth of monolayer tin disulfide(SnS2) remains a great challenge contrasted to transition metal dichalcogenides, which have been studied quite maturely. Till date, there have been scant reports on the growth of large-scale and large-size monolayer SnS2. Here, we successfully synthesized monolayer SnS2 crystal on SiO2/Si substrates via NaCl-assisted CVD and the edge can be as long as 80 μm. Optical microscope, Raman spectroscopy, x-ray diffraction, atomic force microscopy(AFM), and energydispersion x-ray(EDX) were performed respectively to investigate the morphology, crystallographic structure, and optical property of the 2 D SnS2 nanosheets. In addition, we discussed the growing mechanism of the NaCl-assisted CVD method.展开更多
Because of graphene and phosphorene, two-dimensional （2D） layered materials of group IV and group V elements arouse great interest. However, group IV-V monolayers have not received due attention. In this work, three...Because of graphene and phosphorene, two-dimensional （2D） layered materials of group IV and group V elements arouse great interest. However, group IV-V monolayers have not received due attention. In this work, three types of SiP monolayers were computationally designed to explore their electronic structure and optical properties. Computations confirm the stability of these monolayers, which are all indirect-bandgap semiconductors with bandgaps in the range 1.38-2.21 eV. The bandgaps straddle the redox potentials of water at pH = 0, indicating the potential of the monolayers for use as water- splitting photocatalysts. The computed optical properties demonstrate that certain monolayers of SiP 2D materials axe absorbers of visible light and would serve as good candidates for optoelectronic devices.展开更多
基金supported by the National Natural Science Foundation of China(No.1573002)Natural Science Funds for Distinguished Young Scholar of Anhui Province(No.1908085J08)。
文摘On the basis of known structures of 13-GeTe bulk and the derived monolayer,we proposed a series of structural analogues MXs(M=Ge,Sn;X=S,Se,Te)with an intrinsic built-in electric field via a substitution strategy.Using first-principles calculations,we demonstrated that these MX monolayers and bulks are thermodynamically,dynamically and mechanically stable,and the stabilities of bulks are more robust than the monolayer counterparts.Electronic calculations showed that the monolayers have large band gaps ranging from 2.38 to 3.27 eV while the bulks have pronounced small band gaps ranging from 0.06 to 0.78 eV.The calculated piezoelectric coefficients d11 for the MX monolayers are in the range from 6.6 to 10.9 pmN.Strikingly,the calculated d33 for the MX bulks are as high as 40.3-213.7 pm/V.By correlating atomic polarizability,atomic mass,relative ion motion,Bader charge and lattice parameters,we proposed an empirical model to estimate the piezoelectric coefficients for the two-dimensional:(2D)MXs,where a nice match between the estimated ones and the calculated ones was found.The versatile electronic propertiesand large piezoelectric coefficients endow MXs a broad prospect of application in optoelectronic and piezoelectric devices,and the revealed underlying mechanisms offer valuable guidelines for seeking novel piezoelectrics.
基金This project was funded by China Postdoctoral Science Foundation(Grant No.2019M660107)the National Natural Science Foundation of China(Grant No.11804039).
文摘Three-dimensional(3D)topological insulators(TIs)have been studied for approximately fifteen years,but those made from group-IV elements,especially Ge and Sn,seem particularly attractive owing to their nontoxicity,sizable intrinsic spin–orbit coupling(SOC)strength and natural compatibility with the current semiconductor industry.However,group-IV elemental TIs have rarely been reported,except for the low temperature phase ofα-Sn under strain.Here,based on first-principles calculations,we propose new allotropes of Ge and Sn,named T5-Ge/Sn,as desirable TIs.These new allotropes are also highly anisotropic Dirac semimetals if the SOC is turned off.To the best of our knowledge,T5-Ge/Sn are the first 3D allotropes of Ge/Sn that possess topological states in their equilibrium states at room temperature.Additionally,their isostructures of C and Si are metastable indirect and direct semiconductors.Our work not only reveals two promising TIs,but more profoundly,we justify the advantages of group-IV elements as topological quantum materials(TQMs)for fundamental research and potential practical applications,and thus reveal a new direction in the search for desirable TQMs.
基金financially supported by the Shanghai Science and Technology Committee(08DZ2270500,08DJ1400103)Shanghai Leading Academic Discipline Project(B108)the National Basic Research Program of China(2009CB825300,2010DFA41160)
文摘A series of half-sandwich group IV metal complexes with tridentate monoanionic phenoxy-imine arylsulfide [O-NS] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N = CHC6H2O）]- （La） and dianionic phenoxy-amine arylsulfide [O-N-S] ligand [2-Bu^t4-Me-6-（（2-（SC6H5）C6H4N-CH2C6H2O）]2- （Lb） have been synthesized and characterized. Lb was obtained easily in high yield by reduction of ligand La with excess LiAlH4 in cool diethyl ether. Half-sandwich Group Ⅳ metal complexes CpTi[O-NS]Cl2 （1a）, CpZr[O-NS]Cl2 （1b）, CpTi[O-N-S]Cl （2a）, CpZr[O-N-S]Cl （2b） and CpZr[O-N-S]Cl （2c） were synthesized by the reactions of La and Lb with CpTiCl3, CpZrCl3 and Cp ZrCl3, and characterized by IR, ^1H-NMR, ^13C-NMR and elemental analysis. In addition, an X-ray structure analysis was performed on ligand Lb. The title Group IV half-sandwich bearing tridentate [O,N,S] ligands show good catalytic activities for ethylene polymerization in the presence of methylaluminoxane （MAO） as co-catalyst up to 1.58 × 10^7 g-PE.mol-Zr-1.h-1. The good catalytic activities can be maintained even at high temperatures such as 100 ℃ exhibiting the excellent thermal stability for these half-sandwich metal pre-catalysts.
基金Project supported by the National Basic Research Program of China(Grant No.2016YFA0202302)the National Natural Science Foundation of China(Grant Nos.61527817,61875236,61905010,and 61975007)the Overseas Expertise Introduction Center for Discipline Innovation,111 Center,China
文摘As an important member of the two-dimensional layers of metal dichalcogenides family, the two-dimensional(2 D)group IV metal chalcogenides(GIVMCs) have been attracting intensive attention. However, the growth of monolayer tin disulfide(SnS2) remains a great challenge contrasted to transition metal dichalcogenides, which have been studied quite maturely. Till date, there have been scant reports on the growth of large-scale and large-size monolayer SnS2. Here, we successfully synthesized monolayer SnS2 crystal on SiO2/Si substrates via NaCl-assisted CVD and the edge can be as long as 80 μm. Optical microscope, Raman spectroscopy, x-ray diffraction, atomic force microscopy(AFM), and energydispersion x-ray(EDX) were performed respectively to investigate the morphology, crystallographic structure, and optical property of the 2 D SnS2 nanosheets. In addition, we discussed the growing mechanism of the NaCl-assisted CVD method.
基金This work was supported by the National Science Foundation of China （Grant No. 21503195）, Natural Science Foundation of Shanxi Province （2015021044）, and Open Research Fund of Key Laboratory of Advanced Energy Materials Chemistry （Ministry of Education）, Nankai University in China.
文摘Because of graphene and phosphorene, two-dimensional （2D） layered materials of group IV and group V elements arouse great interest. However, group IV-V monolayers have not received due attention. In this work, three types of SiP monolayers were computationally designed to explore their electronic structure and optical properties. Computations confirm the stability of these monolayers, which are all indirect-bandgap semiconductors with bandgaps in the range 1.38-2.21 eV. The bandgaps straddle the redox potentials of water at pH = 0, indicating the potential of the monolayers for use as water- splitting photocatalysts. The computed optical properties demonstrate that certain monolayers of SiP 2D materials axe absorbers of visible light and would serve as good candidates for optoelectronic devices.
