Van der Waals coupling with different stacking configurations can significantly affect the optical and electronic properties of ultrathin two-dimensional(2D)materials,which is an effective way to tune device performan...Van der Waals coupling with different stacking configurations can significantly affect the optical and electronic properties of ultrathin two-dimensional(2D)materials,which is an effective way to tune device performance.Herein,we report a salt-assisted chemical vapor deposition method for the synthesis of bilayer V-doped MoS_(2) with 2H and 3R phases,which are demonstrated by the second harmonic generation and scanning transmission electron microscopy.Notably,the mobility of the 3R phase V-doped MoS_(2) is 6.2%higher than that of the 2H phase.Through first-principles calculations,we further reveal that this particular behavior is attributed to the stronger interlayer coupling of 3R compared to the 2H stacking configuration.This research can be further generalized to other transition metal chalcogenides and will contribute to the development of electronic devices based on 2D materials in the future.展开更多
Optical excitations of the hybrids,which are assembled by coupling single-walled carbon nanotubes(SWCNTs)with organic molecules through van der Waals interactions,are studied using ab initio manybody Green’s function...Optical excitations of the hybrids,which are assembled by coupling single-walled carbon nanotubes(SWCNTs)with organic molecules through van der Waals interactions,are studied using ab initio manybody Green’s function theory.We take the semiconducting(7,0)SWCNT,the squarylium and oligothiophene molecules as the example.The E11 and E22 absorption peaks of the(7,0)tube can be redshifted by tens of meV.Most importantly,the lowest dark exciton of the(7,0)tube at the lower-energy side of E11 can be brightened by the interaction between the nanotube and molecules.Position of this new satellite absorption peak is influenced by the type of adsorbed molecule.These findings may be useful for tuning the emission energy and emission efficiency of CNTs.展开更多
In this work,a new superhard material named Pm BN is proposed.The structural properties,stability,mechanical properties,mechanical anisotropy properties,and electronic properties of Pm BN are studied in this work.Pm B...In this work,a new superhard material named Pm BN is proposed.The structural properties,stability,mechanical properties,mechanical anisotropy properties,and electronic properties of Pm BN are studied in this work.Pm BN is dynamically and mechanically stable,the relative enthalpy of Pm BN is greater than that of c-BN,and in this respect,and it is more favorable than that of T-B_(3)N_(3),T-B_(7)N_(7),tP24 BN,Imm2 BN,Ni As BN,and rocksalt BN.The Young's modulus,bulk modulus,and shear modulus of Pm BN are 327 GPa,331 GPa,and 738 GPa,respectively,and according to Chen's model,Pm BN is a novel superhard material.Compared with its original structure,the mechanical anisotropy of Young's modulus of Pm BN is larger than that of C14 carbon.Finally,the calculations of the electronic energy band structure show that Pm BN is a semiconductor material with not only a wide band gap but also an indirect band gap.展开更多
Terbium aluminum garnet(Tb_(3)Al_(5)O_(12);TAG)ceramics are among the most promising magneto–optical materials owing to their outstanding comprehensive performance.Many works have focused on improving the optical qua...Terbium aluminum garnet(Tb_(3)Al_(5)O_(12);TAG)ceramics are among the most promising magneto–optical materials owing to their outstanding comprehensive performance.Many works have focused on improving the optical quality of TAG ceramics.A key point for improving optical quality is ensuring the accuracy of the stoichiometric ratio and avoiding secondary phases.In this work,0,2,4,or 6 wt%Sc_(2)O_(3) was added to the TAG ceramics to increase the solid solubility.The effects of Sc substitution on the crystal structure,sintering process,microstructure,optical transmittance,and magneto–optical properties of(Tb_(1−x)Sc_(x))_(3)(Al_(1−y)Sc_(y))_(2)Al_(3)O_(12)(TSAG)ceramics are studied in detail.4 wt%Sc2O3:TAG ceramics with an in-line transmittance of 82.2%at 1064 nm and 81.2%at 633 nm were successfully fabricated,and the Verdet constant was 164.4 rad·T^(−1)·m^(−1) at 633 nm.Anti-site defects(ADs)and Sc replacement in TAG are further studied via first-principles calculations to determine the working mechanism of Sc.Both the experimental and calculation results show that the introduction of Sc can effectively increase the solid solubility of TAG ceramics,suppress secondary phases,and hence improve the optical transmittance.展开更多
Two-dimensional layered materials(2DLMs)have attracted growing attention in optoelectronic devices due to their intriguing anisotropic physical properties.Different members of 2DLMs exhibit unique anisotropic electric...Two-dimensional layered materials(2DLMs)have attracted growing attention in optoelectronic devices due to their intriguing anisotropic physical properties.Different members of 2DLMs exhibit unique anisotropic electrical,optical,and thermal properties,fundamentally related to their crystal structure.Among them,directional heat transfer plays a vital role in the thermal management of electronic devices.Here,we use density functional theory calculations to investigate the thermal transport properties of representative layered materials:β-InSe,γ-InSe,MoS2,and h-BN.We found that the lattice thermal conductivities ofβ-InSe,γ-InSe,MoS_(2),and h-BN display diverse anisotropic behaviors with anisotropy ratios of 10.4,9.4,64.9,and 107.7,respectively.The analysis of the phonon modes further indicates that the phonon group velocity is responsible for the anisotropy of thermal transport.Furthermore,the low lattice thermal conductivity of the layered InSe mainly comes from low phonon group velocity and atomic masses.Our findings provide a fundamental physical understanding of the anisotropic thermal transport in layered materials.We hope this study could inspire the advancement of 2DLMs thermal management applications in next-generation integrated electronic and optoelectronic devices.展开更多
Two-dimensional(2D)semiconductors exhibit great potential to minimize the size and drastically reduce the energy consumption of optoelectronic devices due to promising features induced by quantum confinement.It has ac...Two-dimensional(2D)semiconductors exhibit great potential to minimize the size and drastically reduce the energy consumption of optoelectronic devices due to promising features induced by quantum confinement.It has achieved many successes in infra-red and visible light optoelectronic devices.The study on ultra-wide band gap 2D semiconductors except h-BN are still limited,however,the requirement is more and more urgent.Inspired by the progresses of III-nitride semiconductors in recent several decades,2D AlN is highly expected to be a new member of ultra-wide band gap 2D semiconductors.In this work,we employed the first-principles calculations to investigate the structural and electronic properties of 2D AlN.We revealed that few-layer AlN acquires a square-octagon(so-AlN)configuration in the vertical direction when the number of atomic layers n is smaller than 16.With increasing the thickness from 2 ML to 8 ML,the band gap decreased due to the weakening of quantum confinement effect.We demonstrated the intrinsic indirect band gap can be tuned to be direct by applying different direction strains for so-AlN.Our results open new avenues for their application in nano-optoelectronics.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.62174013 and92265111)the Funding Program of Beijing Institute of Technology (Nos.3180012212214 and 3180023012204)。
文摘Van der Waals coupling with different stacking configurations can significantly affect the optical and electronic properties of ultrathin two-dimensional(2D)materials,which is an effective way to tune device performance.Herein,we report a salt-assisted chemical vapor deposition method for the synthesis of bilayer V-doped MoS_(2) with 2H and 3R phases,which are demonstrated by the second harmonic generation and scanning transmission electron microscopy.Notably,the mobility of the 3R phase V-doped MoS_(2) is 6.2%higher than that of the 2H phase.Through first-principles calculations,we further reveal that this particular behavior is attributed to the stronger interlayer coupling of 3R compared to the 2H stacking configuration.This research can be further generalized to other transition metal chalcogenides and will contribute to the development of electronic devices based on 2D materials in the future.
基金supported by the National Natural Science Foundation of China(No.21833004)。
文摘Optical excitations of the hybrids,which are assembled by coupling single-walled carbon nanotubes(SWCNTs)with organic molecules through van der Waals interactions,are studied using ab initio manybody Green’s function theory.We take the semiconducting(7,0)SWCNT,the squarylium and oligothiophene molecules as the example.The E11 and E22 absorption peaks of the(7,0)tube can be redshifted by tens of meV.Most importantly,the lowest dark exciton of the(7,0)tube at the lower-energy side of E11 can be brightened by the interaction between the nanotube and molecules.Position of this new satellite absorption peak is influenced by the type of adsorbed molecule.These findings may be useful for tuning the emission energy and emission efficiency of CNTs.
基金supported by the National Natural Science Foundation of China(Grant No.61804120)China Postdoctoral Science Foundation(Nos.2019TQ0243,2019M663646)+4 种基金Natural Science Basic Research Program of Shaanxi(2021JQ-515)Key scientific research plan of Education Department of Shaanxi Provincial Government(Key Laboratory Project)(No.20JS066)Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20190110)National Key Research and Development Program of China(No.2018YFB1502902)Key Program for International S&T Cooperation Projects of Shaanxi Province(No.2019KWZ-03)。
文摘In this work,a new superhard material named Pm BN is proposed.The structural properties,stability,mechanical properties,mechanical anisotropy properties,and electronic properties of Pm BN are studied in this work.Pm BN is dynamically and mechanically stable,the relative enthalpy of Pm BN is greater than that of c-BN,and in this respect,and it is more favorable than that of T-B_(3)N_(3),T-B_(7)N_(7),tP24 BN,Imm2 BN,Ni As BN,and rocksalt BN.The Young's modulus,bulk modulus,and shear modulus of Pm BN are 327 GPa,331 GPa,and 738 GPa,respectively,and according to Chen's model,Pm BN is a novel superhard material.Compared with its original structure,the mechanical anisotropy of Young's modulus of Pm BN is larger than that of C14 carbon.Finally,the calculations of the electronic energy band structure show that Pm BN is a semiconductor material with not only a wide band gap but also an indirect band gap.
基金supported by the National Key R&D Program of China(Grant No.2023YFB3812000)the General Project of Shanghai Natural Science Foundation(Grant No.22ZR1471500)the Prospective Basic Research and Applied Basic Research of Hengdian Group.
文摘Terbium aluminum garnet(Tb_(3)Al_(5)O_(12);TAG)ceramics are among the most promising magneto–optical materials owing to their outstanding comprehensive performance.Many works have focused on improving the optical quality of TAG ceramics.A key point for improving optical quality is ensuring the accuracy of the stoichiometric ratio and avoiding secondary phases.In this work,0,2,4,or 6 wt%Sc_(2)O_(3) was added to the TAG ceramics to increase the solid solubility.The effects of Sc substitution on the crystal structure,sintering process,microstructure,optical transmittance,and magneto–optical properties of(Tb_(1−x)Sc_(x))_(3)(Al_(1−y)Sc_(y))_(2)Al_(3)O_(12)(TSAG)ceramics are studied in detail.4 wt%Sc2O3:TAG ceramics with an in-line transmittance of 82.2%at 1064 nm and 81.2%at 633 nm were successfully fabricated,and the Verdet constant was 164.4 rad·T^(−1)·m^(−1) at 633 nm.Anti-site defects(ADs)and Sc replacement in TAG are further studied via first-principles calculations to determine the working mechanism of Sc.Both the experimental and calculation results show that the introduction of Sc can effectively increase the solid solubility of TAG ceramics,suppress secondary phases,and hence improve the optical transmittance.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1402502)the National Natural Science Foundation of China(Grant Nos.12004131,22090044,and 62125402)Calculations were performed in part at the high-performance computing center of Jilin University.
文摘Two-dimensional layered materials(2DLMs)have attracted growing attention in optoelectronic devices due to their intriguing anisotropic physical properties.Different members of 2DLMs exhibit unique anisotropic electrical,optical,and thermal properties,fundamentally related to their crystal structure.Among them,directional heat transfer plays a vital role in the thermal management of electronic devices.Here,we use density functional theory calculations to investigate the thermal transport properties of representative layered materials:β-InSe,γ-InSe,MoS2,and h-BN.We found that the lattice thermal conductivities ofβ-InSe,γ-InSe,MoS_(2),and h-BN display diverse anisotropic behaviors with anisotropy ratios of 10.4,9.4,64.9,and 107.7,respectively.The analysis of the phonon modes further indicates that the phonon group velocity is responsible for the anisotropy of thermal transport.Furthermore,the low lattice thermal conductivity of the layered InSe mainly comes from low phonon group velocity and atomic masses.Our findings provide a fundamental physical understanding of the anisotropic thermal transport in layered materials.We hope this study could inspire the advancement of 2DLMs thermal management applications in next-generation integrated electronic and optoelectronic devices.
基金This work was supported by the National Natural Science Foundation of China[61804152,61834008].
文摘Two-dimensional(2D)semiconductors exhibit great potential to minimize the size and drastically reduce the energy consumption of optoelectronic devices due to promising features induced by quantum confinement.It has achieved many successes in infra-red and visible light optoelectronic devices.The study on ultra-wide band gap 2D semiconductors except h-BN are still limited,however,the requirement is more and more urgent.Inspired by the progresses of III-nitride semiconductors in recent several decades,2D AlN is highly expected to be a new member of ultra-wide band gap 2D semiconductors.In this work,we employed the first-principles calculations to investigate the structural and electronic properties of 2D AlN.We revealed that few-layer AlN acquires a square-octagon(so-AlN)configuration in the vertical direction when the number of atomic layers n is smaller than 16.With increasing the thickness from 2 ML to 8 ML,the band gap decreased due to the weakening of quantum confinement effect.We demonstrated the intrinsic indirect band gap can be tuned to be direct by applying different direction strains for so-AlN.Our results open new avenues for their application in nano-optoelectronics.
