Similar to high performance SnSe thermoelectrics, SnSe2 is also a layered structured semiconductor.However, its anisotropic thermoelectric properties are less experimentally investigated. In this work,Cl-doped SnSe2 b...Similar to high performance SnSe thermoelectrics, SnSe2 is also a layered structured semiconductor.However, its anisotropic thermoelectric properties are less experimentally investigated. In this work,Cl-doped SnSe2 bulk materials are successfully prepared, and their thermal stability and anisotropic transport properties are systematically studied. Unexpectedly, different from the theoretical prediction and other typical layered thermoelectric compounds like Bi_2Te_3, the out-of-plane zT_c value is higher than in-plane zT_a for the same composition. The zT value is significantly enhanced by Cl doping. A maximum zT_c of ~0.4 at 673 K is achieved in SnSe_(1.88)Cl_(0.12), twice higher than previously reported Cl-doped SnSe_2 synthesized by the solvothermal method.展开更多
Thermoelectric selenides have attracted more and more attentions recently.Herein,p-type Sn Se polycrystalline bulk materials with good thermoelectric properties are presented.By using the SnSe2 nanostructures synthesi...Thermoelectric selenides have attracted more and more attentions recently.Herein,p-type Sn Se polycrystalline bulk materials with good thermoelectric properties are presented.By using the SnSe2 nanostructures synthesized via a wetchemistry route as the precursor,polycrystalline Sn Se bulk materials were successfully obtained by a combined heattreating process under reducing atmosphere and following spark plasma sintering procedure.As a reference,the Sn Se nanostructures synthesized via a wet-chemistry route were also fabricated into polycrystalline bulk materials through the same process.The thermoelectric properties of the Sn Se polycrystalline transformed from SnSe2 nanostructures indicate that the increasing of heattreating temperature could effectively decrease the electrical resistivity,whereas the decrease in Seebeck coefficient is nearly invisible.As a result,the maximum power factor is enhanced from 5.06×10^-4W/m·K^2 to 8.08×10^-4W/m·K^2 at 612℃.On the other hand,the reference sample,which was obtained by using Sn Se nanostructures as the precursor,displays very poor power factor of only 1.30×10^-4W/m·K^2 at 537℃.The x-ray diffraction（XRD）,scanning electron microscope（SEM）,x-ray fluorescence（XRF）,and Hall effect characterizations suggest that the anisotropic crystal growth and existing Sn vacancy might be responsible for the enhanced electrical transport in the polycrystalline Sn Se prepared by using SnSe2 precursor.On the other hand,the impact of heat-treating temperature on thermal conductivity is not obvious.Owing to the boosting of power factor,a high z T value of 1.07 at 612℃ is achieved.This study provides a new method to synthesize polycrystalline Sn Se and pave a way to improve the thermoelectric properties of polycrystalline bulk materials with similar layered structure.展开更多
Thin films of SnSe and SnSe2 have been deposited using the ultrasonic spray pyrolysis（USP） technique.To the best of our knowledge this is the first report of the deposition of SnSe and SnSe2 thin films using a singl...Thin films of SnSe and SnSe2 have been deposited using the ultrasonic spray pyrolysis（USP） technique.To the best of our knowledge this is the first report of the deposition of SnSe and SnSe2 thin films using a single spray solution.The use of a single spray solution for obtaining both a p-type material,SnSe,and an n-type material,SnSe2,simplifies the deposition technique.The SnSe2 thin films have a bandgap of 1.1 eV and the SnSe thin films have a band gap of 0.9 eV.The Hall measurements were used to determine the resistivity of the thin films.The SnSe2 thin films show a resistivity of 36.73 Ωcm and n-type conductivity while the SnSe thin films show a resistivity of 180 Ωcm and p-type conductivity.展开更多
二硒化锡(SnSe_(2))具有高理论比容量、原料广泛、成本低廉等优点,是一种十分有前途的钠离子电池负极材料,但同时在实际充放电过程中也受限于体积膨胀导致的结构破坏问题。鉴于此,本文通过高温煅烧的方法成功合成了碳包覆的二硒化锡(SnS...二硒化锡(SnSe_(2))具有高理论比容量、原料广泛、成本低廉等优点,是一种十分有前途的钠离子电池负极材料,但同时在实际充放电过程中也受限于体积膨胀导致的结构破坏问题。鉴于此,本文通过高温煅烧的方法成功合成了碳包覆的二硒化锡(SnSe_(2)@C)。碳包覆提高了二硒化锡材料作为钠离子电池负极的导电性和稳定性,使得Sn Se_(2)@C具有优异的高比容量(在1.0 A·g^(-1)下,比容量为549.0 m Ah·g^(-1))和倍率性能(在5.0 A·g^(-1)下,比容量为427.7 m Ah·g^(-1))。展开更多
Superconducting metal dichalcogenides(MDCs)present several similarities to the other layered SI1-perconductors like cuprates.The superconductivity in atomically thin MDCs has been demonstrated by recent experiments,ho...Superconducting metal dichalcogenides(MDCs)present several similarities to the other layered SI1-perconductors like cuprates.The superconductivity in atomically thin MDCs has been demonstrated by recent experiments,however,the investigation of the superconductivity intertwined with other or-ders are scarce.Investigating the pseudogap in atomic layers of MDCs may help to understand the superconducting mechanism for these true two dimensional(2D)superconducting systemns.Herein we report a pseudogap opening in the tunneling spectra of thin layers of SnSe2 epitaxially grown on highly oriented pyrolytic graphite(HOPG)with scanning tunneling microscopy/spectroscopy(STM/STS).A significant V-shaped pseudogap was observed to open near the Fermi level(Er)in the sTS.And at elevated temperatures,the gap gradually evolves to a shallow dip.Our experimental observations provide direct evidence of a pseudogap state in the electron-doped SnSe2 atomic layers on the HOPG surface,which may stimulate further exploration of the mechanism of superconductivity at 2D limit in MDCs.展开更多
Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the doub...Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the double-walled hollow carbon spheres(DWHCSs),in which N and Se atoms were doped in the carbon walls,to construct SnSe_(2)@N,Se-DWHCSs by confined growth and in-situ derivatization.The N and Sedoped DWHCSs can effectively limit the size increase of SnSe_(2),promote ion diffusion kinetics,and buffer volume expansion,which can be proved by electron microscope observation and density functional theory calculation.Consequently,the SnSe_(2)@N,Se-DWHCSs as an anode material for sodium ion batteries(SIBs)demonstrated a distinguished reversible capacity of 322.8 mAh g^(-1)at 5 A g^(-1)after 1000 cycles and a superior rate ability of 235.3 m Ah g^(-1)at an ultrahigh rate of 15 A g^(-1).Furthermore,the structure evolution and electrochemical reaction processes of SnSe2@N,Se-DWHCSs in SIBs were analyzed by exsitu methods,which confirmed the consecutive hybrid mechanism and the phase transition process.展开更多
Two-dimensional(2D)tin diselenide(SnSe2),a novel layered material with excellent optical and electronic properties,has been extensively investigated in various promising applications,including photodetectors,optical s...Two-dimensional(2D)tin diselenide(SnSe2),a novel layered material with excellent optical and electronic properties,has been extensively investigated in various promising applications,including photodetectors,optical switching,and ultrafast photonics.In this work,SnSe2 nanosheets have been obtained after pretreatment in an alkaloid,exhibiting high optical absorption and electron-enriched properties.Besides,the performances of the prepared SnSe2 in near-infrared(NIR)and mid-infrared(MIR)ultrafast photonics are presented.Notably,by employing the SnSe2-deposited microfiber device as a saturable absorber(SA)exhibiting typical nonlinear optical absorption properties,stable ultrashort pulses and rogue waves are realized in an erbium-doped fiber laser.Furthermore,the SnSe2-deposited SA device is also applied to a thulium-doped fiber laser to achieve stable ultrashort pulses.This study indicates that SnSe2 is expected to be a suitable candidate for ultrafast fiber lasers in the NIR and MIR regions.展开更多
SnSe,possessing strong lattice anharmonicity and structural anisotropy,has attracted massive attention in thermoelectric conversion.Herein,we demonstrate that simultaneously optimized electrical and thermal transport ...SnSe,possessing strong lattice anharmonicity and structural anisotropy,has attracted massive attention in thermoelectric conversion.Herein,we demonstrate that simultaneously optimized electrical and thermal transport properties are achieved in SnS_(2) -alloyed SnSe polycrystalline materials,which were fabricated via sintering the mixture of solution-synthesized SnSe microplates and SnS_(2) nanoplates.Resulting from the increased carrier concentration,p-type(SnSe)_(1–x)(SnS_(2))_(x)(x=0.5%,1%)samples obtain muchimproved power factor between 300 K and 373 K,e.g.0.72 mW m^(–1)K^(–2)at 300 K for(SnSe)0.99(SnS_(2) )0.01,which is enhanced by 53%compared to that of SnSe.Additionally,the existing point defects and planar defects effectively strengthen phonon scattering,thus reducing the lattice thermal conductivity,for example,0.47 W m^(–1) K^(–1) at 773 K for the x=0.02 sample.Eventually,a maximum zT of 0.80 at 823 K and an average zT of 0.52 over 300–823 K are obtained in the(SnSe)0.99(SnS_(2))0.01 sample,which are increased by 33%and 45%compared to those of SnSe,respectively.This study demonstrates a secondary phase alloying strategy to synergistically optimize the electrical and thermal properties of polycrystalline SnSe.展开更多
基金supported by the National Natural Science Fund for Distinguished Young Scholars (51725102)the National Natural Science Foundation of China (11574267, 51571177 and 61534001)
文摘Similar to high performance SnSe thermoelectrics, SnSe2 is also a layered structured semiconductor.However, its anisotropic thermoelectric properties are less experimentally investigated. In this work,Cl-doped SnSe2 bulk materials are successfully prepared, and their thermal stability and anisotropic transport properties are systematically studied. Unexpectedly, different from the theoretical prediction and other typical layered thermoelectric compounds like Bi_2Te_3, the out-of-plane zT_c value is higher than in-plane zT_a for the same composition. The zT value is significantly enhanced by Cl doping. A maximum zT_c of ~0.4 at 673 K is achieved in SnSe_(1.88)Cl_(0.12), twice higher than previously reported Cl-doped SnSe_2 synthesized by the solvothermal method.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51572049,51562005,and 51772056)the Natural Science Foundation of Guangxi Zhuang Automomous Region,China(Grant Nos.2015GXNSFFA139002 and 2016GXNSFBA380152)the Open Fund of Key Laboratory of Cryogenics,Technical Institute of Physics and Chemistry,Chinese Academy of Sciences(Grant No.CRYO201703)
文摘Thermoelectric selenides have attracted more and more attentions recently.Herein,p-type Sn Se polycrystalline bulk materials with good thermoelectric properties are presented.By using the SnSe2 nanostructures synthesized via a wetchemistry route as the precursor,polycrystalline Sn Se bulk materials were successfully obtained by a combined heattreating process under reducing atmosphere and following spark plasma sintering procedure.As a reference,the Sn Se nanostructures synthesized via a wet-chemistry route were also fabricated into polycrystalline bulk materials through the same process.The thermoelectric properties of the Sn Se polycrystalline transformed from SnSe2 nanostructures indicate that the increasing of heattreating temperature could effectively decrease the electrical resistivity,whereas the decrease in Seebeck coefficient is nearly invisible.As a result,the maximum power factor is enhanced from 5.06×10^-4W/m·K^2 to 8.08×10^-4W/m·K^2 at 612℃.On the other hand,the reference sample,which was obtained by using Sn Se nanostructures as the precursor,displays very poor power factor of only 1.30×10^-4W/m·K^2 at 537℃.The x-ray diffraction（XRD）,scanning electron microscope（SEM）,x-ray fluorescence（XRF）,and Hall effect characterizations suggest that the anisotropic crystal growth and existing Sn vacancy might be responsible for the enhanced electrical transport in the polycrystalline Sn Se prepared by using SnSe2 precursor.On the other hand,the impact of heat-treating temperature on thermal conductivity is not obvious.Owing to the boosting of power factor,a high z T value of 1.07 at 612℃ is achieved.This study provides a new method to synthesize polycrystalline Sn Se and pave a way to improve the thermoelectric properties of polycrystalline bulk materials with similar layered structure.
基金carried out with financial assistance from the DGAPA- PAPIIT project (IN 113409)
文摘Thin films of SnSe and SnSe2 have been deposited using the ultrasonic spray pyrolysis（USP） technique.To the best of our knowledge this is the first report of the deposition of SnSe and SnSe2 thin films using a single spray solution.The use of a single spray solution for obtaining both a p-type material,SnSe,and an n-type material,SnSe2,simplifies the deposition technique.The SnSe2 thin films have a bandgap of 1.1 eV and the SnSe thin films have a band gap of 0.9 eV.The Hall measurements were used to determine the resistivity of the thin films.The SnSe2 thin films show a resistivity of 36.73 Ωcm and n-type conductivity while the SnSe thin films show a resistivity of 180 Ωcm and p-type conductivity.
文摘二硒化锡(SnSe_(2))具有高理论比容量、原料广泛、成本低廉等优点,是一种十分有前途的钠离子电池负极材料,但同时在实际充放电过程中也受限于体积膨胀导致的结构破坏问题。鉴于此,本文通过高温煅烧的方法成功合成了碳包覆的二硒化锡(SnSe_(2)@C)。碳包覆提高了二硒化锡材料作为钠离子电池负极的导电性和稳定性,使得Sn Se_(2)@C具有优异的高比容量(在1.0 A·g^(-1)下,比容量为549.0 m Ah·g^(-1))和倍率性能(在5.0 A·g^(-1)下,比容量为427.7 m Ah·g^(-1))。
基金We thank Prof.Tao Wu for helpful discus.sion.This work was supported by the National Key R&D Program of China(Grant Nos.2016YFA0200603 and 2017YFA0205004)the"Strategic Priority Research Program"of CAS(Grant No.XDB01020100)+2 种基金the National Natural Science Foundation of China(Grant Nos.91321309,21421063,and 21473174)the Funda-mental Research Funds for the Central Science Advances Universi-ties(Nos.WK2060190027 and WK2060190084)A.Z.acknowledges a fellowship from the Youth Innovation Promotion Association of CAS(No.2011322)。
文摘Superconducting metal dichalcogenides(MDCs)present several similarities to the other layered SI1-perconductors like cuprates.The superconductivity in atomically thin MDCs has been demonstrated by recent experiments,however,the investigation of the superconductivity intertwined with other or-ders are scarce.Investigating the pseudogap in atomic layers of MDCs may help to understand the superconducting mechanism for these true two dimensional(2D)superconducting systemns.Herein we report a pseudogap opening in the tunneling spectra of thin layers of SnSe2 epitaxially grown on highly oriented pyrolytic graphite(HOPG)with scanning tunneling microscopy/spectroscopy(STM/STS).A significant V-shaped pseudogap was observed to open near the Fermi level(Er)in the sTS.And at elevated temperatures,the gap gradually evolves to a shallow dip.Our experimental observations provide direct evidence of a pseudogap state in the electron-doped SnSe2 atomic layers on the HOPG surface,which may stimulate further exploration of the mechanism of superconductivity at 2D limit in MDCs.
基金The funding support from the Natural Science Research Project of Jiangsu Higher Education Institutions(Grant No.21KJA530004)the 2021 Young Scientist Exchange Program between the Republic of Korea and the People’s Republic of Chinaa Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the double-walled hollow carbon spheres(DWHCSs),in which N and Se atoms were doped in the carbon walls,to construct SnSe_(2)@N,Se-DWHCSs by confined growth and in-situ derivatization.The N and Sedoped DWHCSs can effectively limit the size increase of SnSe_(2),promote ion diffusion kinetics,and buffer volume expansion,which can be proved by electron microscope observation and density functional theory calculation.Consequently,the SnSe_(2)@N,Se-DWHCSs as an anode material for sodium ion batteries(SIBs)demonstrated a distinguished reversible capacity of 322.8 mAh g^(-1)at 5 A g^(-1)after 1000 cycles and a superior rate ability of 235.3 m Ah g^(-1)at an ultrahigh rate of 15 A g^(-1).Furthermore,the structure evolution and electrochemical reaction processes of SnSe2@N,Se-DWHCSs in SIBs were analyzed by exsitu methods,which confirmed the consecutive hybrid mechanism and the phase transition process.
基金Science,Technology and Innovation Commission of Shenzhen Municipality(JCYJ20190806163805286,JCYJ20190808143813399)Taipei University of Technology–Shenzhen University Joint Research Program(2020007)+2 种基金Natural Science Foundation of Guangdong Province(2019A1515111060,2020A151501787)China Postdoctoral Science Foundation(2019M660212)National Natural Science Foundation of China(61705140,61805115,61875132,61875138).
文摘Two-dimensional(2D)tin diselenide(SnSe2),a novel layered material with excellent optical and electronic properties,has been extensively investigated in various promising applications,including photodetectors,optical switching,and ultrafast photonics.In this work,SnSe2 nanosheets have been obtained after pretreatment in an alkaloid,exhibiting high optical absorption and electron-enriched properties.Besides,the performances of the prepared SnSe2 in near-infrared(NIR)and mid-infrared(MIR)ultrafast photonics are presented.Notably,by employing the SnSe2-deposited microfiber device as a saturable absorber(SA)exhibiting typical nonlinear optical absorption properties,stable ultrashort pulses and rogue waves are realized in an erbium-doped fiber laser.Furthermore,the SnSe2-deposited SA device is also applied to a thulium-doped fiber laser to achieve stable ultrashort pulses.This study indicates that SnSe2 is expected to be a suitable candidate for ultrafast fiber lasers in the NIR and MIR regions.
基金financially supported by the National Natural Science Foundation of China(Nos.51802034,52071041,11904039,11874356)the Natural Science Foundation of Chongqing(No.cstc2021jcyj-msxm X0407)。
文摘SnSe,possessing strong lattice anharmonicity and structural anisotropy,has attracted massive attention in thermoelectric conversion.Herein,we demonstrate that simultaneously optimized electrical and thermal transport properties are achieved in SnS_(2) -alloyed SnSe polycrystalline materials,which were fabricated via sintering the mixture of solution-synthesized SnSe microplates and SnS_(2) nanoplates.Resulting from the increased carrier concentration,p-type(SnSe)_(1–x)(SnS_(2))_(x)(x=0.5%,1%)samples obtain muchimproved power factor between 300 K and 373 K,e.g.0.72 mW m^(–1)K^(–2)at 300 K for(SnSe)0.99(SnS_(2) )0.01,which is enhanced by 53%compared to that of SnSe.Additionally,the existing point defects and planar defects effectively strengthen phonon scattering,thus reducing the lattice thermal conductivity,for example,0.47 W m^(–1) K^(–1) at 773 K for the x=0.02 sample.Eventually,a maximum zT of 0.80 at 823 K and an average zT of 0.52 over 300–823 K are obtained in the(SnSe)0.99(SnS_(2))0.01 sample,which are increased by 33%and 45%compared to those of SnSe,respectively.This study demonstrates a secondary phase alloying strategy to synergistically optimize the electrical and thermal properties of polycrystalline SnSe.
