By using the first-principles calculations, the electronic properties of graphene nanoribbon （GNR） doped by boron/nitrogen （B/N） bonded pair are investigated. It is found that B/N bonded pair tends to be doped at ...By using the first-principles calculations, the electronic properties of graphene nanoribbon （GNR） doped by boron/nitrogen （B/N） bonded pair are investigated. It is found that B/N bonded pair tends to be doped at the edges of GNR and B/N pair doping in GNR is easier to carry out than single B doping and unbonded B/N co-doping in GNR. The electronic structure of GNR doped by B/N pair is very sensitive to doping site besides the ribbon width and chirality. Moreover, B/N pair doping can selectively adjust the energy gap of armchair GNR and can induce the semimetal-semiconductor transmission for zigzag GNR. This fact may lead to a possible method for energy band engineering of GNRs and benefit the design of graphene electronic device.展开更多
An amorphous SiO2/4 H–Si C（0001） interface model with carbon dimer defects is established based on density functional theory of the first-principle plane wave pseudopotential method.The structures of carbon dimer d...An amorphous SiO2/4 H–Si C（0001） interface model with carbon dimer defects is established based on density functional theory of the first-principle plane wave pseudopotential method.The structures of carbon dimer defects after passivation by H2 and NO molecules are established,and the interface states before and after passivation are calculated by the Heyd–Scuseria–Ernzerhof（HSE06） hybrid functional scheme.Calculation results indicate that H2 can be adsorbed on the O2–C = C–O2 defect and the carbon–carbon double bond is converted into a single bond.However,H2 cannot be adsorbed on the O2–（C = C）′ –O2 defect.The NO molecules can be bonded by N and C atoms to transform the carbon–carbon double bonds,thereby passivating the two defects.This study shows that the mechanism for the passivation of Si O2/4 H–SiC（0001） interface carbon dimer defects is to convert the carbon–carbon double bonds into carbon dimers.Moreover,some intermediate structures that can be introduced into the interface state in the band gap should be avoided.展开更多
Due to the magnetic bistability, single-molecule spin-crossover (SCO) complexes have been considered to be the most promising building blocks for molecular spintronic devices. Here, we explore the SCO behavior and coh...Due to the magnetic bistability, single-molecule spin-crossover (SCO) complexes have been considered to be the most promising building blocks for molecular spintronic devices. Here, we explore the SCO behavior and coherent spin transport properties of a six-coordinate FeN6 complex with the low-spin (LS) and high-spin (HS) states by performing extensive first-principles calculations combined with non-equilibrium Green’s function technique. Theoretical results show that the LS$HS spin transition via changing the metal-ligand bond lengths can be realized by external stimuli, such as under light radiation in experiments. According to the calculated zero-bias transmission coefficients and density of states as well as the I-V curves under small bias voltages of FeN6 SCO complex with the LS and HS states sandwiched between two Au electrodes, we find that the examined molecular junction can act as a molecular switch, tuning from the OFF (LS) state to the ON (HS) state. Moreover, the spin-down electrons govern the current of the HS molecular junction, and this observed perfect spin-filtering effect is not sensitive to the detailed anchoring structure. These theoretical findings highlight this examined six-coordinate FeN6 SCO complex for potential applications in molecular spintronics.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
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
As the homologous compounds of MoSi_(2)N_(4),the MoSi_(2)N_(4)(MoN)n monolay-ers have been synthesized in a recent experiment.These systems consist of homogeneous metal nitride multilayers sandwiched between two SiN s...As the homologous compounds of MoSi_(2)N_(4),the MoSi_(2)N_(4)(MoN)n monolay-ers have been synthesized in a recent experiment.These systems consist of homogeneous metal nitride multilayers sandwiched between two SiN surfaces,which extends the septuple-atomic-layer MSizN4 system to ultra-thick MSi2N4(MN)n forms.In this paper,we perform a first-principles study on the MoSizN4(FeN)monolayer,which is constructed by iron molybdenum nitride intercalated into the SiN layers.As a cousin of MoSi_(2)N_(4)(MoN),this double transition-metal system exhibits robust struc-tural stability from the energetic,mechanical,dynamical and thermal perspectives.Different from the MoSi_(2)N_(4)(MoN)one,the MoSi_(2)N_(4)(FeN)monolayer possesses intrinsic ferromagnetism and presents a bipolar magnetic semiconducting behaviour.The ferromagnetism can be further enhanced by the surface hydrogenation,which raises the Curie tempera-ture to 310 K around room temperature.More interestingly,the hydro-genated MoSi_(2)N_(4)(FeN)monolayer exhibits a quantum anomalous Hall(QAH)insulating behaviour with a sizeable nontrivial band gap of 0.23 eV.The nontrivial topological character can be well described by a two-band k·p model,confirming a non-zero Chern number of C=1.Similar bipolar magnetic semiconducting feature and hydrogenation-induced QAH state are also present in the WSizN4(FeN)monolayer.Our study demonstrates that the double transition-metal MSi2N4(M'N)system will be a fertile plat-form to achieve fascinating spintronic and topological properties.展开更多
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
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
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
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supported by the Science and Technology Program of Hunan Province,China (Grant No.2010DFJ411)the Natural Science Foundation of Hunan Province,China (Grant No.11JJ4001)the Fundamental Research Funds for the Central Universities,China (Grant No.201012200053)
文摘By using the first-principles calculations, the electronic properties of graphene nanoribbon （GNR） doped by boron/nitrogen （B/N） bonded pair are investigated. It is found that B/N bonded pair tends to be doped at the edges of GNR and B/N pair doping in GNR is easier to carry out than single B doping and unbonded B/N co-doping in GNR. The electronic structure of GNR doped by B/N pair is very sensitive to doping site besides the ribbon width and chirality. Moreover, B/N pair doping can selectively adjust the energy gap of armchair GNR and can induce the semimetal-semiconductor transmission for zigzag GNR. This fact may lead to a possible method for energy band engineering of GNRs and benefit the design of graphene electronic device.
基金Project supported by the National Natural Science Foundation of China(Grant No.61474013)
文摘An amorphous SiO2/4 H–Si C（0001） interface model with carbon dimer defects is established based on density functional theory of the first-principle plane wave pseudopotential method.The structures of carbon dimer defects after passivation by H2 and NO molecules are established,and the interface states before and after passivation are calculated by the Heyd–Scuseria–Ernzerhof（HSE06） hybrid functional scheme.Calculation results indicate that H2 can be adsorbed on the O2–C = C–O2 defect and the carbon–carbon double bond is converted into a single bond.However,H2 cannot be adsorbed on the O2–（C = C）′ –O2 defect.The NO molecules can be bonded by N and C atoms to transform the carbon–carbon double bonds,thereby passivating the two defects.This study shows that the mechanism for the passivation of Si O2/4 H–SiC（0001） interface carbon dimer defects is to convert the carbon–carbon double bonds into carbon dimers.Moreover,some intermediate structures that can be introduced into the interface state in the band gap should be avoided.
基金the National Key Research & Development Program of China (No.2016YFA0200600) and the National Natural Science Foundation of China (No.21873088 and No.11634011). Computational resources are provided by Chinese Academy Sciences, Shanghai and University of Science and Technology Supercomputer Centers.
文摘Due to the magnetic bistability, single-molecule spin-crossover (SCO) complexes have been considered to be the most promising building blocks for molecular spintronic devices. Here, we explore the SCO behavior and coherent spin transport properties of a six-coordinate FeN6 complex with the low-spin (LS) and high-spin (HS) states by performing extensive first-principles calculations combined with non-equilibrium Green’s function technique. Theoretical results show that the LS$HS spin transition via changing the metal-ligand bond lengths can be realized by external stimuli, such as under light radiation in experiments. According to the calculated zero-bias transmission coefficients and density of states as well as the I-V curves under small bias voltages of FeN6 SCO complex with the LS and HS states sandwiched between two Au electrodes, we find that the examined molecular junction can act as a molecular switch, tuning from the OFF (LS) state to the ON (HS) state. Moreover, the spin-down electrons govern the current of the HS molecular junction, and this observed perfect spin-filtering effect is not sensitive to the detailed anchoring structure. These theoretical findings highlight this examined six-coordinate FeN6 SCO complex for potential applications in molecular spintronics.
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 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support from the National Natural Science Foundation of China(No.11774312).
文摘As the homologous compounds of MoSi_(2)N_(4),the MoSi_(2)N_(4)(MoN)n monolay-ers have been synthesized in a recent experiment.These systems consist of homogeneous metal nitride multilayers sandwiched between two SiN surfaces,which extends the septuple-atomic-layer MSizN4 system to ultra-thick MSi2N4(MN)n forms.In this paper,we perform a first-principles study on the MoSizN4(FeN)monolayer,which is constructed by iron molybdenum nitride intercalated into the SiN layers.As a cousin of MoSi_(2)N_(4)(MoN),this double transition-metal system exhibits robust struc-tural stability from the energetic,mechanical,dynamical and thermal perspectives.Different from the MoSi_(2)N_(4)(MoN)one,the MoSi_(2)N_(4)(FeN)monolayer possesses intrinsic ferromagnetism and presents a bipolar magnetic semiconducting behaviour.The ferromagnetism can be further enhanced by the surface hydrogenation,which raises the Curie tempera-ture to 310 K around room temperature.More interestingly,the hydro-genated MoSi_(2)N_(4)(FeN)monolayer exhibits a quantum anomalous Hall(QAH)insulating behaviour with a sizeable nontrivial band gap of 0.23 eV.The nontrivial topological character can be well described by a two-band k·p model,confirming a non-zero Chern number of C=1.Similar bipolar magnetic semiconducting feature and hydrogenation-induced QAH state are also present in the WSizN4(FeN)monolayer.Our study demonstrates that the double transition-metal MSi2N4(M'N)system will be a fertile plat-form to achieve fascinating spintronic and topological properties.
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 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.
