TiNi-based shape memory alloys have been extensively investigated due to their significant applications,but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system w...TiNi-based shape memory alloys have been extensively investigated due to their significant applications,but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system with martensitic transformations(MT) is still lacking.In this work,we focused on the electronic transport behavior of three phases in Ni_(50-x)Fe_xTi_(50)across the MT.A phase diagram of Ni_(50-x)Fe_xTi_(50) was established based on x-ray diffraction,calorimetric,magnetic,and electrical measurements.To reveal the driving force of MT,phonon softening was revealed using first-principles calculations.Notably,the transverse and longitudinal transport behavior changed significantly across the phase transition,which can be attributed to the reconstruction of electronic structures.This work promotes the understanding of phase transitions and demonstrates the sensitivity of electron transport to phase transition.展开更多
In recent years, two-dimensional boron sheets (borophene) have been experimentally synthesized and theoretically proposed as a promising conductor or transistor with novel thermal and electronic properties. We first...In recent years, two-dimensional boron sheets (borophene) have been experimentally synthesized and theoretically proposed as a promising conductor or transistor with novel thermal and electronic properties. We first give a general survey of some notable electronic properties of borophene, including the superconductivity and topological characters. We then mainly review the basic approaches, thermal transport, as well as the mechanical properties of borophene with different configurations. This review gives a general understanding of some of the crucial thermal transport and electronic properties of borophene, and also calls for further experimental investigations and applications on certain scientific community.展开更多
The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons(AGNRs)with different widths are investigated by applying the non-equilibrium Green's function...The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons(AGNRs)with different widths are investigated by applying the non-equilibrium Green's function formalism combined with first-principles density functional theory.The calculated results show that the width and doping play significant roles in the electronic transport properties of the molecular junction.A higher current can be obtained for the molecular junctions with the tailoring AGNRs with W=11.Furthermore,the current of boron-doped tailoring AGNRs with widths W=7 is nearly four times larger than that of the undoped one,which can be potentially useful for the design of high performance electronic devices.展开更多
A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecu...A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 (2007)]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.展开更多
By, introducing the random and systematic errors in simulated data computed from conventional frequency-scan and laterally resolved modulated free carrier absorption theory models, we investigate the relative determin...By, introducing the random and systematic errors in simulated data computed from conventional frequency-scan and laterally resolved modulated free carrier absorption theory models, we investigate the relative determination sensitivities of three electronic transport properties, namely, carrier lifetime carrier diffusivity and front surface recombination velocity of silicon wafers determined by frequency-scan and laterally resolved techniques. The phase and amplitude data with random errors as functions of the modulation frequency at zero pump-probe-beam separation or of the two-beam separation at four different modulation frequencies are simultaneously fitted to an appreciated carrier diffusion model to extract three transport parameters. The statistical results and fitted accuracies of the transport parameter determined by both techniques are theoretically analysed. Corresponding experimental results are carried out to compare to the simulated results. The simulated and experimental results show that the determination of the transport properties of silicon wafers by the laterally resolved technique are more accurate, as compared with that by the frequency-scan technique.展开更多
We studied and compared the transport properties of charge carriers in bilayer graphene, monolayer graphene, and the conventional semiconductors (the two-dimensional electron gas (2DEG)). It is elucidated that the...We studied and compared the transport properties of charge carriers in bilayer graphene, monolayer graphene, and the conventional semiconductors (the two-dimensional electron gas (2DEG)). It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene. However, resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene, which do not occur in the 2DEG. Furthermore, there are tunneling and forbidden regions in the transmission spectrum for each material, and the division of the two regions has been given in the work. The tunneling region covers a wide range of the incident energy for the two graphene systems, but only exists under specific conditions for the 2DEG. The counterparts of the transmission in the conductance profile are also given for the three materials, which may be used as high-performance devices based on the bilayer graphene.展开更多
Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular...Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. ~urthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.展开更多
We focus on two new 21) materials, i.e., monolayer and bilayer silicon phosphides (Sil P1). Based on the elastic- scattering Green's function, the electronic-transport properties of two-dimensional monolayer and b...We focus on two new 21) materials, i.e., monolayer and bilayer silicon phosphides (Sil P1). Based on the elastic- scattering Green's function, the electronic-transport properties of two-dimensional monolayer and bilayer Au- Si1P1-Au molecular junctions are studied. It is found that their bandgaps are narrow (0.16eV for a monolayer molecular junction and 0.26 e V for a bilayer molecular junction). Moreover, the calculated current-voltage char- acteristics indicate that the monolayer molecular junction provides constant output current (20 hA) over a wide voltage range, and the bilayer molecular junction provides higher current (42 hA).展开更多
We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-princ...We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-principles method based on density functional theory. Among the three models M1–M3, M1 is not doped with a heteroatom. In the left parts of M2 and M3, nitrogen atoms are doped at two edges of the nanoribbon. In the right parts, nitrogen atoms are doped at one center and at the edges of M2 and M3, respectively. Comparisons of M1, M2 and M3 show obvious rectifying characteristics, and the maximum rectification ratios are up to 42.9 in M2. The results show that the rectifying behavior is strongly dependent on the doping position of electrodes. A higher rectification ratio can be found in the dipyrimidinyl-diphenyl molecular device with asymmetric doping of left and right electrodes, which suggests that this system has a broader application in future logic and memory devices.展开更多
We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green's function theory. In the process of...We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green's function theory. In the process of replacing the P atoms with Si atoms every other line from the middle of monolayer blue phosphorus molecular structure, the substitution of Si atoms changes the properties of Au-P-Au molecular junction significantly. Interestingly, the current value has a symmetric change as a parabolic curve with the peak appearing in Au-Si_1P_1-Au molecular junction, which provides the most stable current of 15.00 nA in a wide voltage range of 0.70-2.70 V.Moreover, the current-voltage characteristics of the structures indicate that the steps tend to disappear revealing the property similar to metal when the Si atoms dominate the molecular junction.展开更多
Pr_(0.5)Sr_(0.5)FeO_(3)(PSFO)and La_(0.25)Pr_(0.25)Sr_(0.5)FeO_(3)(LPSFO)nanofibers are prepared by electrospinning followed by calcination,and their morphologies,microstructures,electronic transports,and magnetic pro...Pr_(0.5)Sr_(0.5)FeO_(3)(PSFO)and La_(0.25)Pr_(0.25)Sr_(0.5)FeO_(3)(LPSFO)nanofibers are prepared by electrospinning followed by calcination,and their morphologies,microstructures,electronic transports,and magnetic properties are studied systematically.The temperature-dependent resistance curves of PSFO and LPSFO nanofibers are measured in a temperature range from 300 K to 10 K.With the temperature lowering,the resistance increases gradually and then decreases sharply due to the occurrence of ferromagnetic metal phase.The metal-insulator transition temperatures are about 110 K and 180 K for PSFO and LPSFO nanofibers,respectively.The electronic conduction behavior above the transition temperature can be described by one-dimensional Mott’s variable-range hopping(VRH)model.The hysteresis loops and the field-cooled(FC)and zero-field-cooled(ZFC)curves show that both PSFO nanofiber and LPSFO nanofiber exhibit ferromagnetism.Although the doping of La reduces the overall magnetization intensity of the material,it increases the ferromagnetic ratio of the system,which may improve the performance of LPSFO in solid oxide fuel cell.展开更多
The electronic structure and thermoelectric(TE) properties of Mg2GexSn1-x(x = 0.25, 0.50, 0.75) solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special qu...The electronic structure and thermoelectric(TE) properties of Mg2GexSn1-x(x = 0.25, 0.50, 0.75) solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure(SQS) is used to model the solid solutions, which can produce reasonable band gaps with respect to experimental results.The n-type solid solutions have an excellent thermoelectric performance with maximum zT values exceeding 2.0, where the combination of low lattice thermal conductivity and high power factor(PF) plays an important role. These values are higher than those of pure Mg2Sn and Mg2Ge. The p-type solid solutions are inferior to the n-type ones, mainly due to the much lower PF. The maximum zT value of 0.62 is predicted for p-type Mg2Ge(0.25)Sn(0.75) at 800K. The results suggest that the n-type Mg2GexSn1-x solid solutions are promising mid-temperature TE materials.展开更多
Using the one atom theory, the electronic structures of pure Cr, Mo and W with bcc structure were determined respectively as: [Ar] (3d c) 3.32 (3d n) 2.26 (4s c) 0.25 (4s f) 0.17 , [Kr] (4d c) 4.23 (4d n) 1.48 (5s c) ...Using the one atom theory, the electronic structures of pure Cr, Mo and W with bcc structure were determined respectively as: [Ar] (3d c) 3.32 (3d n) 2.26 (4s c) 0.25 (4s f) 0.17 , [Kr] (4d c) 4.23 (4d n) 1.48 (5s c) 0.02 (5s f) 0.27 and [Xe](5d c) 5.16 (6s c) 0.25 (6s f) 0.59 .The electronic structures of these metals with hcp and fcc structures and liquid state were also studied. According to their electronic structures, the relationship between the electronic structure and crystalline structure was explained qualitatively and the relationship between the difference of mechanical properties and transport properties of pure Cr, Mo and W with bcc structure and their electronic structures was also explained qualitatively; the lattice constants, binding energy, potential curves, elasticities and the temperature dependence of the linear thermal expansion coefficient of bcc Cr, bcc Mo and bcc W were calculated quantitatively.展开更多
Transport properties on the surface of a topological insulator (TI) under the modulation of a two-dimensional (2D) ferromagnet/ferromagnet junction are investigated by the method of wave function matching. The sin...Transport properties on the surface of a topological insulator (TI) under the modulation of a two-dimensional (2D) ferromagnet/ferromagnet junction are investigated by the method of wave function matching. The single ferromagnetic barrier modulated transmission probability is expected to be a periodic function of the polarization angle and the planar rotation angle, that decreases with the strength of the magnetic proximity exchange increasing. However, the transmission probability for the double ferromagnetic insulators modulated n-n junction and n-p junction is not a periodic function of polarization angle nor planar rotation angle, owing to the combined effects of the double ferromagnetic insulators and the barrier potential. Since the energy gap between the conduction band and the valence band is narrowed and widened respectively in ranges of 0 ≤ 0 〈π/2 and r/2 〈 0 ≤ π, the transmission probability of the n-n junction first increases rapidly and then decreases slowly with the increase of the magnetic proximity exchange strength. While the transmission probability for the n-p junction demonstrates an opposite trend on the strength of the magnetic proximity exchange because the band gaps contrarily vary. The obtained results may lead to the possible realization of a magnetic/electric switch based on TIs and be useful in further understanding the surface states of TIs.展开更多
The novel linear, circular, hooped, and helical molecules based on oligo[8]thio- phene were theoretically studied for the applications of charge transfer devices. To investigate the influence of topology for oligo[8]t...The novel linear, circular, hooped, and helical molecules based on oligo[8]thio- phene were theoretically studied for the applications of charge transfer devices. To investigate the influence of topology for oligo[8]thiophene derivatives, the geometry structures, frontier molecular orbital (FMO) energies, charge transport properties, and stability property were predicted by density functional theory methods. The calculated results reported herein show that the oligo[8]thiophene derivative with linear structure has smaller energy gap, and fused oligo[8]thiophene derivative with circular structure has the smallest reorganization energy among the designed molecules. We have also studied the stability properties of the designed molecules, and oligo[8]thiophene derivatives are more stable tharJ the fused oligo[8]thiophene derivatives.展开更多
By employing non-equilibrium Green's function combined with the spin-polarized density-functional theory, we investigate the spin-dependent electronic transport properties of armchair arsenene nanoribbons(a As NRs)...By employing non-equilibrium Green's function combined with the spin-polarized density-functional theory, we investigate the spin-dependent electronic transport properties of armchair arsenene nanoribbons(a As NRs). Our results show that the spin-metal and spin-semiconductor properties can be observed in a As NRs with different widths. We also find that there is nearly 100% bipolar spin-filtering behavior in the a As NR-based device with antiparallel spin configuration. Moreover, rectifying behavior and giant magnetoresistance are found in the device. The corresponding physical analyses have been given.展开更多
By using nonequilibrium Green's function method and first-principles calculations, the electronic transport properties of doped C60 molecular devices were investigated. It is revealed that the C60 molecular device...By using nonequilibrium Green's function method and first-principles calculations, the electronic transport properties of doped C60 molecular devices were investigated. It is revealed that the C60 molecular devices show the metal behavior due to the interaction between the C60 molecule and the metal electrode. The current-voltage curve displays a linear behavior at low bias, and the currents have the relation of M1>M3>M4>M2 when the bias voltage is lower than 0.6 V. Electronic transport properties are affected greatly by the doped atoms. Negative differential resistance is found in a certain bias range for C60 and C58BN molecular devices, but cannot be observed in C59B and C59N molecular devices. These unconventional effects can be used to design novel nanoelectronic devices.展开更多
Using the first principles calculation and Boltzmann transport theory, we study the thermoelectric properties of Si2BNadsorbing halogen atoms (Si2BN-4X, X = F, Cl, Br, and I). The results show that the adsorption of h...Using the first principles calculation and Boltzmann transport theory, we study the thermoelectric properties of Si2BNadsorbing halogen atoms (Si2BN-4X, X = F, Cl, Br, and I). The results show that the adsorption of halogen atoms cansignificantly regulate the energy band structure and lattice thermal conductivity of Si2BN. Among them, Si2BN-4I has thebest thermoelectric performance, the figure of merit can reach 0.50 K at 300 K, which is about 16 times greater than that ofSi2BN. This is because the adsorption of iodine atoms not only significantly increases the Seebeck coefficient due to banddegeneracy, but also rapidly reduces the phonon thermal conductivity by enhancing phonon scattering. Our work proves theapplication potential of Si2BN-based crystals in the field of thermoelectricity and the effective method for metal crystals toopen bandgaps by adsorbing halogens.展开更多
基金supported by the State Key Development Program for Basic Research of China(Grant Nos.2019YFA0704900 and 2022YFA1403800)the Fundamental Science Center of the National Natural Science Foundation of China(Grant No.52088101)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant No.XDB33000000)the Synergetic Extreme Condition User Facility(SECUF)the Scientific Instrument Developing Project of CAS(Grant No.ZDKYYQ20210003)。
文摘TiNi-based shape memory alloys have been extensively investigated due to their significant applications,but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system with martensitic transformations(MT) is still lacking.In this work,we focused on the electronic transport behavior of three phases in Ni_(50-x)Fe_xTi_(50)across the MT.A phase diagram of Ni_(50-x)Fe_xTi_(50) was established based on x-ray diffraction,calorimetric,magnetic,and electrical measurements.To reveal the driving force of MT,phonon softening was revealed using first-principles calculations.Notably,the transverse and longitudinal transport behavior changed significantly across the phase transition,which can be attributed to the reconstruction of electronic structures.This work promotes the understanding of phase transitions and demonstrates the sensitivity of electron transport to phase transition.
文摘In recent years, two-dimensional boron sheets (borophene) have been experimentally synthesized and theoretically proposed as a promising conductor or transistor with novel thermal and electronic properties. We first give a general survey of some notable electronic properties of borophene, including the superconductivity and topological characters. We then mainly review the basic approaches, thermal transport, as well as the mechanical properties of borophene with different configurations. This review gives a general understanding of some of the crucial thermal transport and electronic properties of borophene, and also calls for further experimental investigations and applications on certain scientific community.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11004156 and 11547172the Science and Technology Star Project of Shaanxi Province under Grant No 2016KJXX-45
文摘The electronic transport properties of a molecular junction based on doping tailoring armchair-type graphene nanoribbons(AGNRs)with different widths are investigated by applying the non-equilibrium Green's function formalism combined with first-principles density functional theory.The calculated results show that the width and doping play significant roles in the electronic transport properties of the molecular junction.A higher current can be obtained for the molecular junctions with the tailoring AGNRs with W=11.Furthermore,the current of boron-doped tailoring AGNRs with widths W=7 is nearly four times larger than that of the undoped one,which can be potentially useful for the design of high performance electronic devices.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10804064 and 10674084)
文摘A first-principles computational method based on the hybrid density functional theory is developed to simulate the electronic transport properties of oligomeric phenylene ethynylene molecular junctions with H2O molecules accumulated in the vicinity as recently reported by Na et al. [Nanotechnology 18 424001 (2007)]. The numerical results show that the hydrogen bonds between the oxygen atoms of the oligomeric phenylene ethynylene molecule and H2O molecules result in the localisation of the molecular orbitals and lead to the lower transition peaks. The H2O molecular chains accumulated in the vicinity of the molecular junction can not only change the electronic structure of the molecular junctions, but also open additional electronic transport pathways. The obvious influence of H2O molecules on the electronic structure of the molecular junction and its electronic transport properties is thus demonstrated.
基金Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. ZYGX2009J051)
文摘By, introducing the random and systematic errors in simulated data computed from conventional frequency-scan and laterally resolved modulated free carrier absorption theory models, we investigate the relative determination sensitivities of three electronic transport properties, namely, carrier lifetime carrier diffusivity and front surface recombination velocity of silicon wafers determined by frequency-scan and laterally resolved techniques. The phase and amplitude data with random errors as functions of the modulation frequency at zero pump-probe-beam separation or of the two-beam separation at four different modulation frequencies are simultaneously fitted to an appreciated carrier diffusion model to extract three transport parameters. The statistical results and fitted accuracies of the transport parameter determined by both techniques are theoretically analysed. Corresponding experimental results are carried out to compare to the simulated results. The simulated and experimental results show that the determination of the transport properties of silicon wafers by the laterally resolved technique are more accurate, as compared with that by the frequency-scan technique.
基金the National Natural Science Foundation of China(Grant No.11104156)the Postdoctoral Science Foundation of China(Grant No.2012M510405)+1 种基金the Independent Research and Development Fund of Tsinghua University,China(Grant No.20121087948)the Beijing Key Lab of Fine Ceramics Opening Fund,China(Grant No.2012200110)
文摘We studied and compared the transport properties of charge carriers in bilayer graphene, monolayer graphene, and the conventional semiconductors (the two-dimensional electron gas (2DEG)). It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene. However, resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene, which do not occur in the 2DEG. Furthermore, there are tunneling and forbidden regions in the transmission spectrum for each material, and the division of the two regions has been given in the work. The tunneling region covers a wide range of the incident energy for the two graphene systems, but only exists under specific conditions for the 2DEG. The counterparts of the transmission in the conductance profile are also given for the three materials, which may be used as high-performance devices based on the bilayer graphene.
基金Supported by the National Natural Science Foundation of China under Grant No 11004156the Natural Science Foundation of Shaanxi Province under Grant No 2014JM1025+2 种基金the Science and Technology Star Project of Shaanxi Province under Grant No2016KJXX-38the Special Foundation of Key Academic Subjects Development of Shaanxi Province under Grant No 2008-169the Xi'an Polytechnic University Young Scholar Supporting Plan under Grant No 2013-06
文摘Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. ~urthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.
基金Supported by the National Natural Science Foundation of China under Grant No 11374033
文摘We focus on two new 21) materials, i.e., monolayer and bilayer silicon phosphides (Sil P1). Based on the elastic- scattering Green's function, the electronic-transport properties of two-dimensional monolayer and bilayer Au- Si1P1-Au molecular junctions are studied. It is found that their bandgaps are narrow (0.16eV for a monolayer molecular junction and 0.26 e V for a bilayer molecular junction). Moreover, the calculated current-voltage char- acteristics indicate that the monolayer molecular junction provides constant output current (20 hA) over a wide voltage range, and the bilayer molecular junction provides higher current (42 hA).
基金Supported by the National Natural Science Foundation of China under Grant Nos 11504283 and 21503153the Natural Science Foundation of Shaanxi Province under Grant No 2014JM1025the Science and Technology Star Project of Shaanxi Province under Grant No 2016KJXX-45
文摘We investigate the electronic transport properties of dipyrimidinyl-diphenyl sandwiched between two armchair graphene nanoribbon electrodes using the nonequilibrium Green function formalism combined with a first-principles method based on density functional theory. Among the three models M1–M3, M1 is not doped with a heteroatom. In the left parts of M2 and M3, nitrogen atoms are doped at two edges of the nanoribbon. In the right parts, nitrogen atoms are doped at one center and at the edges of M2 and M3, respectively. Comparisons of M1, M2 and M3 show obvious rectifying characteristics, and the maximum rectification ratios are up to 42.9 in M2. The results show that the rectifying behavior is strongly dependent on the doping position of electrodes. A higher rectification ratio can be found in the dipyrimidinyl-diphenyl molecular device with asymmetric doping of left and right electrodes, which suggests that this system has a broader application in future logic and memory devices.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11374033,11774030,51735001 and 61775016the Fundamental Research Funds for the Central Universities under Grant No 2017CX10007
文摘We investigate the electronic-transport properties of two-dimensional monolayer films from Au-P-Au molecular junction to Au-Si-Au molecular junction using elastic scattering Green's function theory. In the process of replacing the P atoms with Si atoms every other line from the middle of monolayer blue phosphorus molecular structure, the substitution of Si atoms changes the properties of Au-P-Au molecular junction significantly. Interestingly, the current value has a symmetric change as a parabolic curve with the peak appearing in Au-Si_1P_1-Au molecular junction, which provides the most stable current of 15.00 nA in a wide voltage range of 0.70-2.70 V.Moreover, the current-voltage characteristics of the structures indicate that the steps tend to disappear revealing the property similar to metal when the Si atoms dominate the molecular junction.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51973100 and 11904193)the Fund from the State Key Laboratory of Bio-Fibers and Eco-Textiles,Qingdao University,China(Grant No.RZ2000003334)the National Key Research and Development Project,China(Grant No.2019YFC0121402)。
文摘Pr_(0.5)Sr_(0.5)FeO_(3)(PSFO)and La_(0.25)Pr_(0.25)Sr_(0.5)FeO_(3)(LPSFO)nanofibers are prepared by electrospinning followed by calcination,and their morphologies,microstructures,electronic transports,and magnetic properties are studied systematically.The temperature-dependent resistance curves of PSFO and LPSFO nanofibers are measured in a temperature range from 300 K to 10 K.With the temperature lowering,the resistance increases gradually and then decreases sharply due to the occurrence of ferromagnetic metal phase.The metal-insulator transition temperatures are about 110 K and 180 K for PSFO and LPSFO nanofibers,respectively.The electronic conduction behavior above the transition temperature can be described by one-dimensional Mott’s variable-range hopping(VRH)model.The hysteresis loops and the field-cooled(FC)and zero-field-cooled(ZFC)curves show that both PSFO nanofiber and LPSFO nanofiber exhibit ferromagnetism.Although the doping of La reduces the overall magnetization intensity of the material,it increases the ferromagnetic ratio of the system,which may improve the performance of LPSFO in solid oxide fuel cell.
基金supported by the National Natural Science Foundation of China(Grant No.11647010)the Foundation from the Higher Education and High-quality and World-class Universities(Grant No.PY201611)
文摘The electronic structure and thermoelectric(TE) properties of Mg2GexSn1-x(x = 0.25, 0.50, 0.75) solid solutions are investigated by first-principles calculations and semi-classical Boltzmann theory. The special quasi-random structure(SQS) is used to model the solid solutions, which can produce reasonable band gaps with respect to experimental results.The n-type solid solutions have an excellent thermoelectric performance with maximum zT values exceeding 2.0, where the combination of low lattice thermal conductivity and high power factor(PF) plays an important role. These values are higher than those of pure Mg2Sn and Mg2Ge. The p-type solid solutions are inferior to the n-type ones, mainly due to the much lower PF. The maximum zT value of 0.62 is predicted for p-type Mg2Ge(0.25)Sn(0.75) at 800K. The results suggest that the n-type Mg2GexSn1-x solid solutions are promising mid-temperature TE materials.
文摘Using the one atom theory, the electronic structures of pure Cr, Mo and W with bcc structure were determined respectively as: [Ar] (3d c) 3.32 (3d n) 2.26 (4s c) 0.25 (4s f) 0.17 , [Kr] (4d c) 4.23 (4d n) 1.48 (5s c) 0.02 (5s f) 0.27 and [Xe](5d c) 5.16 (6s c) 0.25 (6s f) 0.59 .The electronic structures of these metals with hcp and fcc structures and liquid state were also studied. According to their electronic structures, the relationship between the electronic structure and crystalline structure was explained qualitatively and the relationship between the difference of mechanical properties and transport properties of pure Cr, Mo and W with bcc structure and their electronic structures was also explained qualitatively; the lattice constants, binding energy, potential curves, elasticities and the temperature dependence of the linear thermal expansion coefficient of bcc Cr, bcc Mo and bcc W were calculated quantitatively.
基金supported by the National Natural Science Foundation of China(Grant Nos.11264013 and 11147021)the Hunan Provincial Natural Science Foundation of China(Grant No.12JJ4003)the Research Program for Employee of Jishou University,China(Grant No.jsdxkyzz201005)
文摘Transport properties on the surface of a topological insulator (TI) under the modulation of a two-dimensional (2D) ferromagnet/ferromagnet junction are investigated by the method of wave function matching. The single ferromagnetic barrier modulated transmission probability is expected to be a periodic function of the polarization angle and the planar rotation angle, that decreases with the strength of the magnetic proximity exchange increasing. However, the transmission probability for the double ferromagnetic insulators modulated n-n junction and n-p junction is not a periodic function of polarization angle nor planar rotation angle, owing to the combined effects of the double ferromagnetic insulators and the barrier potential. Since the energy gap between the conduction band and the valence band is narrowed and widened respectively in ranges of 0 ≤ 0 〈π/2 and r/2 〈 0 ≤ π, the transmission probability of the n-n junction first increases rapidly and then decreases slowly with the increase of the magnetic proximity exchange strength. While the transmission probability for the n-p junction demonstrates an opposite trend on the strength of the magnetic proximity exchange because the band gaps contrarily vary. The obtained results may lead to the possible realization of a magnetic/electric switch based on TIs and be useful in further understanding the surface states of TIs.
基金Supported by the National Natural Science Foundation of China(No.21302062)the Science Foundation for Young Teachers of Jilin Agricultural University(No.201219)
文摘The novel linear, circular, hooped, and helical molecules based on oligo[8]thio- phene were theoretically studied for the applications of charge transfer devices. To investigate the influence of topology for oligo[8]thiophene derivatives, the geometry structures, frontier molecular orbital (FMO) energies, charge transport properties, and stability property were predicted by density functional theory methods. The calculated results reported herein show that the oligo[8]thiophene derivative with linear structure has smaller energy gap, and fused oligo[8]thiophene derivative with circular structure has the smallest reorganization energy among the designed molecules. We have also studied the stability properties of the designed molecules, and oligo[8]thiophene derivatives are more stable tharJ the fused oligo[8]thiophene derivatives.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21673296 and 11334014)the Science and Technology Plan of Hunan Province,China(Grant No.2015RS4002)the Postdoctoral Science Foundation of Central South University,China
文摘By employing non-equilibrium Green's function combined with the spin-polarized density-functional theory, we investigate the spin-dependent electronic transport properties of armchair arsenene nanoribbons(a As NRs). Our results show that the spin-metal and spin-semiconductor properties can be observed in a As NRs with different widths. We also find that there is nearly 100% bipolar spin-filtering behavior in the a As NR-based device with antiparallel spin configuration. Moreover, rectifying behavior and giant magnetoresistance are found in the device. The corresponding physical analyses have been given.
基金Project(07JJ3102) supported by the Natural Science Foundation of Hunan Province, ChinaProject(1343-74236000006) supported by the Graduate Foundation of Hunan Province, ChinaProject(11MY20) supported by the Mittal Entrepreneurship Program of China
文摘By using nonequilibrium Green's function method and first-principles calculations, the electronic transport properties of doped C60 molecular devices were investigated. It is revealed that the C60 molecular devices show the metal behavior due to the interaction between the C60 molecule and the metal electrode. The current-voltage curve displays a linear behavior at low bias, and the currents have the relation of M1>M3>M4>M2 when the bias voltage is lower than 0.6 V. Electronic transport properties are affected greatly by the doped atoms. Negative differential resistance is found in a certain bias range for C60 and C58BN molecular devices, but cannot be observed in C59B and C59N molecular devices. These unconventional effects can be used to design novel nanoelectronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074115,11874145,and 51775183)the Hunan Provincial Natural Science Fund of China(Grant No.2018JJ2125).
文摘Using the first principles calculation and Boltzmann transport theory, we study the thermoelectric properties of Si2BNadsorbing halogen atoms (Si2BN-4X, X = F, Cl, Br, and I). The results show that the adsorption of halogen atoms cansignificantly regulate the energy band structure and lattice thermal conductivity of Si2BN. Among them, Si2BN-4I has thebest thermoelectric performance, the figure of merit can reach 0.50 K at 300 K, which is about 16 times greater than that ofSi2BN. This is because the adsorption of iodine atoms not only significantly increases the Seebeck coefficient due to banddegeneracy, but also rapidly reduces the phonon thermal conductivity by enhancing phonon scattering. Our work proves theapplication potential of Si2BN-based crystals in the field of thermoelectricity and the effective method for metal crystals toopen bandgaps by adsorbing halogens.