We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons(APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density fun...We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons(APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density functional calculations. It is found that the atomic vacancies are easier to form and detain at the edge region rather than a random distribution through analyzing formation energy and diffusion barrier. The highly local defect states are generated at the vicinity of the Fermi level, and emerge a deep-to-shallow transformation as the width increases after introducing vacancies in APNRs.Moreover, the electrical transport of APNRs with vacancies is enhanced compared to that of the perfect counterparts. Our results provide a theoretical guidance for the further research and applications of PNRs through defect engineering.展开更多
Using a tight binding transfer matrix method, we calculate the complex band structure of armchair graphene nanoribbons. The real part of the complex band structure calculated by the transfer matrix method fits well wi...Using a tight binding transfer matrix method, we calculate the complex band structure of armchair graphene nanoribbons. The real part of the complex band structure calculated by the transfer matrix method fits well with the bulk band structure calculated by a Hermitian matrix. The complex band structure gives extra information on carrier＇s decay behaviour. The imaginary loop connects the conduction and valence band, and can profoundly affect the characteristics of nanoscale electronic device made with graphene nanoribbons. In this work, the complex band structure calculation includes not only the first nearest neighbour interaction, but also the effects of edge bond relaxation and the third nearest neighbour interaction. The band gap is classified into three classes. Due to the edge bond relaxation and the third nearest neighbour interaction term, it opens a band gap for N = 3M- 1. The band gap is almost unchanged for N =3M ＋ 1, but decreased for N = 3M. The maximum imaginary wave vector length provides additional information about the electrical characteristics of graphene nanoribbons, and is also classified into three classes.展开更多
In this study,the structural and electronic properties of armchair graphdiyne nanoribbons,which have different widths are studied using the first principle calculation.The results indicate that all studied AGDYNRs sho...In this study,the structural and electronic properties of armchair graphdiyne nanoribbons,which have different widths are studied using the first principle calculation.The results indicate that all studied AGDYNRs show semiconducting behavior in which the band gap values decrease with the increase of nanoribbons width.The electronic and electrical properties of the graphdiyne sandwiched between two graphene nanoribbons are also investigated.The findings of our study indicate that among 4 investigated n-G-GDY-G-NR structures,the highest current is calculated for n = 3(3-G-GDY-G-NR),due to phase transition.展开更多
Molar binding energy of the boron nitride single-walled zigzag and armchair nanotubes is calculated within the qua-si-classical approach. We find that, in the range of ultra small radii, the binding energy of nanotube...Molar binding energy of the boron nitride single-walled zigzag and armchair nanotubes is calculated within the qua-si-classical approach. We find that, in the range of ultra small radii, the binding energy of nanotubes exhibit an oscil-latory dependence on tube radius. Nanotubes (1,1), (3,0), and (4,0) are predicted to be more stable species among sin-gle-walled boron nitride nanotubes. The obtained binding energies of BN single-walled nanotubes corrected with zero-point vibration energies lies within the interval (12.01-29.39) eV. In particular, molar binding energy of the ul-tra-large-radius tube is determined as 22.95 eV. The spread of the molar zero-point vibration energy of BN nanotubes itself is (0.25-0.33) eV and its limit for ultra-large-radius tubes is estimated as 0.31 eV. The binding energy peak lo-cated at 2.691 ? corresponds to the equilibrium structural parameter of all realized stable BN nanotubular structures.展开更多
The reaction mechanism between CC12 and armchair single-walled carbon nanotubes （ASWCNTs） （3,3） and （4,4） has been studied by semiempirical AM1 and ab initio methods. The activation barriers of CC12 adding to AS...The reaction mechanism between CC12 and armchair single-walled carbon nanotubes （ASWCNTs） （3,3） and （4,4） has been studied by semiempirical AM1 and ab initio methods. The activation barriers of CC12 adding to ASWCNT （3,3） and （4,4） are computed and compared. The lower barrier of CC12 forms cycloaddition isomer on （3,3） maybe because the strain energy of （3,3） is larger than that of （4,4）. Our theoretical results are consistent with the experimental results.展开更多
In this article, the spin-dependent electronic and transport properties of the armchair boron–phosphorous nanoribbons（ABPNRs） are mainly studied by using the non-equilibrium Green function method combined with the ...In this article, the spin-dependent electronic and transport properties of the armchair boron–phosphorous nanoribbons（ABPNRs） are mainly studied by using the non-equilibrium Green function method combined with the spin-polarized density function theory. Our calculated electronic structures indicate that the edge hydrogenated ABPNRs exhibit a ferromagnetic bipolar magnetic semiconductor property, and that the Si atom doping can make ABPNRs convert into up-spin dominated half metal. The spin-resolved transport property results show that the doped devices can realize 100% spinfiltering function, and that the interesting negative differential resistance phenomenon can be observed. Our calculations suggest that the ABPNRs can be constructed as a spin heterojunction by introducing Si doping partially, and it would be used as a spin-diode for nano-spintronics in future.展开更多
We present the behaviors of both dynamical and static charge susceptibilities of doped armchair nanotubes using the Green function approach in the context of Holstein-model Hamiltonian.Specially,the effects of magneti...We present the behaviors of both dynamical and static charge susceptibilities of doped armchair nanotubes using the Green function approach in the context of Holstein-model Hamiltonian.Specially,the effects of magnetization and gap parameter on the the plasmon modes of armchair nanotube are investigated via calculating correlation function of charge density operators.Random phase approximation has been implemented to find the interacting dynamical charge susceptibility.The electrons in this systems interacts with each other by mediation of dispersionless Holstein phonons.Our results show that the increase of gap parameter leads to decreasing intensity of charge collective mode.Also the frequency position of the collective mode tends to higher frequencies due to the gap parameter.Furthermore the number of collective excitation mode decreases with chemical potential in the presence of electron-phonon interaction.Finally the temperature dependence of static charge structure factor of armchair nanotubes is studied.The effects of the gap parameter,magnetization and electron-phonon interaction on the static structure factor are addressed in details.展开更多
This paper studies the electronic transport property through a square potential barrier in armchair-edge graphene nanoribbon （AGNR）. Using the Dirac equation with the continuity condition for wave functions at the i...This paper studies the electronic transport property through a square potential barrier in armchair-edge graphene nanoribbon （AGNR）. Using the Dirac equation with the continuity condition for wave functions at the interfaces between regions with and without a barrier, we calculate the mode-dependent transmission probability for both semiconducting and metallic AGNRs, respectively. It is shown that, by some numerical examples, the transmission probability is generally an oscillating function of the height and range of the barrier for both types of AGNRs. The main difference between the two types of systems is that the magnitude of oscillation for the semiconducting AGNR is larger than that for the metallic one. This fact implies that the electronic transport property for AGNRs depends sensitively on their widths and edge details due to the Dirac nature of fermions in the system.展开更多
We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green＇s function approach in the context of tight binding model Hamiltonian.Specifically...We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green＇s function approach in the context of tight binding model Hamiltonian.Specifically,the effects of magnetic field on the the plasmon modes of armchair graphene nanoribbon are investigated via calculating the correlation function of charge density operators.Our results show that the increase of magnetic field makes the high-frequency plasmon mode for both metallic and insulating cases disappear.We also show that low-frequency plasmon mode for metallic nanoribbon appears due to increase of magnetic field.Furthermore,the number of collective excitation modes increases with ribbon width at zero magnetic field.Finally,the temperature dependence of the static charge structure factor of armchair graphene nanoribbon is studied.The effects of both magnetic field and ribbon width on the static charge structure factor are discussed in detail.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
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
The electronic transport properties of armchair-edged boron nitride nanoribbons（ABNNRs） devices were investigated by the first principle calculations. The calculated results show that the ABNNR device doped with car...The electronic transport properties of armchair-edged boron nitride nanoribbons（ABNNRs） devices were investigated by the first principle calculations. The calculated results show that the ABNNR device doped with carbon atoms in one of the electrodes acts as a high performance nanoribbon rectifier. It is interesting to find that there exists a particular bias-polarity-dependent matching band between two electrodes,leading to a similar current-voltage（I-V） behavior as conventional P-N diodes. The I-V behavior presents a linear positive-bias I-V characteristic,an absolutely negligible leakage current,and a stable rectifying property under a large bias region. The results suggest that C doping might be an effective way to raise ABNNRs devices＇ rectifying performance.展开更多
The atomic edge structure of graphene governs its unique electronic properties with applications in nanoscale electronics and optoelectronics.To fully realize its potential,it is critical to develop a precision etchin...The atomic edge structure of graphene governs its unique electronic properties with applications in nanoscale electronics and optoelectronics.To fully realize its potential,it is critical to develop a precision etching process producing graphene edges along desired directions.Here,we present a novel approach utilizing scanning probe lithography(SPL)facilitated by a mechanochemical atomic attrition process.This technique enables the fabrication of nanopatterns in single-layer graphene from graphene edges,precisely along the crystallographic orientation of zigzag(ZZ)and armchair(AC)edges,without inducing mechanical damage to the surrounding area.Density functional theory(DFT)calculations revealed that the dissociation of CC bonds by the SPL probe is mediated by the formation of interfacial bridge bonds between the graphene edge and the reactive silica surface.This SPL-based mechanochemical etching method enables the construction of various nanodevice structures with specific edge orientations,which allows the exploitation of their electronic properties.展开更多
We have investigated the electronic properties of WTe2 armchair nanoribbons with defects. WTe2 nanoribbons can be categorized depending on the edge structure in two types： armchair and zigzag. WTe2 in its bulk form h...We have investigated the electronic properties of WTe2 armchair nanoribbons with defects. WTe2 nanoribbons can be categorized depending on the edge structure in two types： armchair and zigzag. WTe2 in its bulk form has an indirect band gap but nanoribbons and nanosheets of WTe2 have direct band gaps. Interestingly, the zigzag nanoribbon is metallic while the armchair nanoribbons are semiconducting. Thus they can find applications in device fabrication. Therefore, it is very important to study the effect of defects on the electronic properties of the armchair nanoribbons as these defects can impair the device properties and characteristics. We have considered defects such as： vacancy, rough edge, wrap, ripple and twist in this work. We report the band gap variation with these defects. We have also studied the change in band gap and total energy with varying degrees of wrap, ripple and twist.展开更多
Armchair carbon nanocoils (CNCs) with different geometric parameters are constructed and optimized using a tight-binding (TB) total energy model. The quantum conductance of these nanocoils is simulated employing a π-...Armchair carbon nanocoils (CNCs) with different geometric parameters are constructed and optimized using a tight-binding (TB) total energy model. The quantum conductance of these nanocoils is simulated employing a π-orbital TB model incorporated with the non-equilibrium Green's function theory. Compared with the perfect armchair carbon nanotubes (CNTs) and armchair CNTs with only Stone-Wales (SW) defects, the quantum conductance spectra of the armchair CNCs present distinct gaps around the Fermi level, which are mainly originated from the existence of sp3 carbon in the three-dimensional spiral structures. Moreover, the detailed conductance spectra of the armchair CNCs depend sensitively on their geometric parameters, such as tubular diameter and block-block distance.展开更多
We used nonlinear laser scanning optical microscopy to study atomically thin transition metal dichalcogenides(TMDs)and revealed,with unprecedented resolution,the orientational distribution of armchair directions and t...We used nonlinear laser scanning optical microscopy to study atomically thin transition metal dichalcogenides(TMDs)and revealed,with unprecedented resolution,the orientational distribution of armchair directions and their degree of organization in the two-dimensional(2D)crystal lattice.In particular,we carried out polarization-resolved second-harmonic generation(PSHG)imaging for monolayer WS2 and obtained,with high-precision,the orientation of the main crystallographic axis(armchair orientation)for each individual 120×120 nm^(2) pixel of the 2D crystal area.Such nanoscale resolution was realized by fitting the experimental PSHG images,obtained with sub-micron precision,to a new generalized theoretical model that accounts for the nonlinear optical properties of TMDs.This enabled us to distinguish between different crystallographic domains,locate boundaries and reveal fine structure.As a consequence,we can calculate the mean orientational average of armchair angle distributions in specific regions of interest and define the corresponding standard deviation as a figure-of-merit for the 2D crystal quality.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11574080 and 91833302)。
文摘We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons(APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density functional calculations. It is found that the atomic vacancies are easier to form and detain at the edge region rather than a random distribution through analyzing formation energy and diffusion barrier. The highly local defect states are generated at the vicinity of the Fermi level, and emerge a deep-to-shallow transformation as the width increases after introducing vacancies in APNRs.Moreover, the electrical transport of APNRs with vacancies is enhanced compared to that of the perfect counterparts. Our results provide a theoretical guidance for the further research and applications of PNRs through defect engineering.
基金Project supported by the Fundamental Research Funds for the Central Universities (Grant No. YWF-10-02-040)
文摘Using a tight binding transfer matrix method, we calculate the complex band structure of armchair graphene nanoribbons. The real part of the complex band structure calculated by the transfer matrix method fits well with the bulk band structure calculated by a Hermitian matrix. The complex band structure gives extra information on carrier＇s decay behaviour. The imaginary loop connects the conduction and valence band, and can profoundly affect the characteristics of nanoscale electronic device made with graphene nanoribbons. In this work, the complex band structure calculation includes not only the first nearest neighbour interaction, but also the effects of edge bond relaxation and the third nearest neighbour interaction. The band gap is classified into three classes. Due to the edge bond relaxation and the third nearest neighbour interaction term, it opens a band gap for N = 3M- 1. The band gap is almost unchanged for N =3M ＋ 1, but decreased for N = 3M. The maximum imaginary wave vector length provides additional information about the electrical characteristics of graphene nanoribbons, and is also classified into three classes.
文摘In this study,the structural and electronic properties of armchair graphdiyne nanoribbons,which have different widths are studied using the first principle calculation.The results indicate that all studied AGDYNRs show semiconducting behavior in which the band gap values decrease with the increase of nanoribbons width.The electronic and electrical properties of the graphdiyne sandwiched between two graphene nanoribbons are also investigated.The findings of our study indicate that among 4 investigated n-G-GDY-G-NR structures,the highest current is calculated for n = 3(3-G-GDY-G-NR),due to phase transition.
文摘Molar binding energy of the boron nitride single-walled zigzag and armchair nanotubes is calculated within the qua-si-classical approach. We find that, in the range of ultra small radii, the binding energy of nanotubes exhibit an oscil-latory dependence on tube radius. Nanotubes (1,1), (3,0), and (4,0) are predicted to be more stable species among sin-gle-walled boron nitride nanotubes. The obtained binding energies of BN single-walled nanotubes corrected with zero-point vibration energies lies within the interval (12.01-29.39) eV. In particular, molar binding energy of the ul-tra-large-radius tube is determined as 22.95 eV. The spread of the molar zero-point vibration energy of BN nanotubes itself is (0.25-0.33) eV and its limit for ultra-large-radius tubes is estimated as 0.31 eV. The binding energy peak lo-cated at 2.691 ? corresponds to the equilibrium structural parameter of all realized stable BN nanotubular structures.
基金This work was supported by the National Natural Science Foundation of China (No. 20303010), NKStar HPC Program and the Science Foundation of Nankai University
文摘The reaction mechanism between CC12 and armchair single-walled carbon nanotubes （ASWCNTs） （3,3） and （4,4） has been studied by semiempirical AM1 and ab initio methods. The activation barriers of CC12 adding to ASWCNT （3,3） and （4,4） are computed and compared. The lower barrier of CC12 forms cycloaddition isomer on （3,3） maybe because the strain energy of （3,3） is larger than that of （4,4）. Our theoretical results are consistent with the experimental results.
基金Project supported by the National Natural Science Foundation of China(Grant No.21673296)the Hunan Provincial Natural Science Foundation of China(Grant No.2018JJ2481)the Fundamental Research Funds for the Central Universities of Central South University,China(Grant No.2018zzts328)
文摘In this article, the spin-dependent electronic and transport properties of the armchair boron–phosphorous nanoribbons（ABPNRs） are mainly studied by using the non-equilibrium Green function method combined with the spin-polarized density function theory. Our calculated electronic structures indicate that the edge hydrogenated ABPNRs exhibit a ferromagnetic bipolar magnetic semiconductor property, and that the Si atom doping can make ABPNRs convert into up-spin dominated half metal. The spin-resolved transport property results show that the doped devices can realize 100% spinfiltering function, and that the interesting negative differential resistance phenomenon can be observed. Our calculations suggest that the ABPNRs can be constructed as a spin heterojunction by introducing Si doping partially, and it would be used as a spin-diode for nano-spintronics in future.
文摘We present the behaviors of both dynamical and static charge susceptibilities of doped armchair nanotubes using the Green function approach in the context of Holstein-model Hamiltonian.Specially,the effects of magnetization and gap parameter on the the plasmon modes of armchair nanotube are investigated via calculating correlation function of charge density operators.Random phase approximation has been implemented to find the interacting dynamical charge susceptibility.The electrons in this systems interacts with each other by mediation of dispersionless Holstein phonons.Our results show that the increase of gap parameter leads to decreasing intensity of charge collective mode.Also the frequency position of the collective mode tends to higher frequencies due to the gap parameter.Furthermore the number of collective excitation mode decreases with chemical potential in the presence of electron-phonon interaction.Finally the temperature dependence of static charge structure factor of armchair nanotubes is studied.The effects of the gap parameter,magnetization and electron-phonon interaction on the static structure factor are addressed in details.
基金Project supported by National Natural Science Foundation of China (Grant No. 10974052)Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20060542002)
文摘This paper studies the electronic transport property through a square potential barrier in armchair-edge graphene nanoribbon （AGNR）. Using the Dirac equation with the continuity condition for wave functions at the interfaces between regions with and without a barrier, we calculate the mode-dependent transmission probability for both semiconducting and metallic AGNRs, respectively. It is shown that, by some numerical examples, the transmission probability is generally an oscillating function of the height and range of the barrier for both types of AGNRs. The main difference between the two types of systems is that the magnitude of oscillation for the semiconducting AGNR is larger than that for the metallic one. This fact implies that the electronic transport property for AGNRs depends sensitively on their widths and edge details due to the Dirac nature of fermions in the system.
文摘We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green＇s function approach in the context of tight binding model Hamiltonian.Specifically,the effects of magnetic field on the the plasmon modes of armchair graphene nanoribbon are investigated via calculating the correlation function of charge density operators.Our results show that the increase of magnetic field makes the high-frequency plasmon mode for both metallic and insulating cases disappear.We also show that low-frequency plasmon mode for metallic nanoribbon appears due to increase of magnetic field.Furthermore,the number of collective excitation modes increases with ribbon width at zero magnetic field.Finally,the temperature dependence of the static charge structure factor of armchair graphene nanoribbon is studied.The effects of both magnetic field and ribbon width on the static charge structure factor are discussed in detail.
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supported by the National Natural Science Foundation of China(21401023 and 21374017)Cultivating Fund for Excellent Young Scholar of Fujian Normal University(FJSDJK2012063)Program for Innovative Research Team in Science and Technology in Fujian Province University(IRTSTFJ)
文摘The electronic transport properties of armchair-edged boron nitride nanoribbons（ABNNRs） devices were investigated by the first principle calculations. The calculated results show that the ABNNR device doped with carbon atoms in one of the electrodes acts as a high performance nanoribbon rectifier. It is interesting to find that there exists a particular bias-polarity-dependent matching band between two electrodes,leading to a similar current-voltage（I-V） behavior as conventional P-N diodes. The I-V behavior presents a linear positive-bias I-V characteristic,an absolutely negligible leakage current,and a stable rectifying property under a large bias region. The results suggest that C doping might be an effective way to raise ABNNRs devices＇ rectifying performance.
基金supported by the National Natural Science Foundation of China(Nos.52122507,52350411,and 12002289)the National Key R&D Program of China-Young Scientist Program(No.2023YFB3405500)+1 种基金The Independent Project of State Key Laboratory of Rail Transit Vehicle System(No.2023TPL-T04)Seong H.Kim was supported by the National Science Foundation of the USA(No.CMMI-1912199).
文摘The atomic edge structure of graphene governs its unique electronic properties with applications in nanoscale electronics and optoelectronics.To fully realize its potential,it is critical to develop a precision etching process producing graphene edges along desired directions.Here,we present a novel approach utilizing scanning probe lithography(SPL)facilitated by a mechanochemical atomic attrition process.This technique enables the fabrication of nanopatterns in single-layer graphene from graphene edges,precisely along the crystallographic orientation of zigzag(ZZ)and armchair(AC)edges,without inducing mechanical damage to the surrounding area.Density functional theory(DFT)calculations revealed that the dissociation of CC bonds by the SPL probe is mediated by the formation of interfacial bridge bonds between the graphene edge and the reactive silica surface.This SPL-based mechanochemical etching method enables the construction of various nanodevice structures with specific edge orientations,which allows the exploitation of their electronic properties.
基金the Department of Science and Technology of the government of India for partially funding this work
文摘We have investigated the electronic properties of WTe2 armchair nanoribbons with defects. WTe2 nanoribbons can be categorized depending on the edge structure in two types： armchair and zigzag. WTe2 in its bulk form has an indirect band gap but nanoribbons and nanosheets of WTe2 have direct band gaps. Interestingly, the zigzag nanoribbon is metallic while the armchair nanoribbons are semiconducting. Thus they can find applications in device fabrication. Therefore, it is very important to study the effect of defects on the electronic properties of the armchair nanoribbons as these defects can impair the device properties and characteristics. We have considered defects such as： vacancy, rough edge, wrap, ripple and twist in this work. We report the band gap variation with these defects. We have also studied the change in band gap and total energy with varying degrees of wrap, ripple and twist.
基金supported by the Fundamental Research Funds for the Central Universities of China (Grant No. DUT10ZD211)the National Natural Science Foundation of China (Grant Nos. 51072027 and 40874039)
文摘Armchair carbon nanocoils (CNCs) with different geometric parameters are constructed and optimized using a tight-binding (TB) total energy model. The quantum conductance of these nanocoils is simulated employing a π-orbital TB model incorporated with the non-equilibrium Green's function theory. Compared with the perfect armchair carbon nanotubes (CNTs) and armchair CNTs with only Stone-Wales (SW) defects, the quantum conductance spectra of the armchair CNCs present distinct gaps around the Fermi level, which are mainly originated from the existence of sp3 carbon in the three-dimensional spiral structures. Moreover, the detailed conductance spectra of the armchair CNCs depend sensitively on their geometric parameters, such as tubular diameter and block-block distance.
基金supported by the European Research Infrastructure NFFA-Europeby the EU's H2020 framework program for research and innovation under grant agreement no.654360support from the Stavros Niarchos Foundation within the framework of the project ARCHERS(‘Advancing Young Researchers’Human Capital in Cutting Edge Technologies in the Preservation of Cultural Heritage and the Tackling of Societal Challenges’).
文摘We used nonlinear laser scanning optical microscopy to study atomically thin transition metal dichalcogenides(TMDs)and revealed,with unprecedented resolution,the orientational distribution of armchair directions and their degree of organization in the two-dimensional(2D)crystal lattice.In particular,we carried out polarization-resolved second-harmonic generation(PSHG)imaging for monolayer WS2 and obtained,with high-precision,the orientation of the main crystallographic axis(armchair orientation)for each individual 120×120 nm^(2) pixel of the 2D crystal area.Such nanoscale resolution was realized by fitting the experimental PSHG images,obtained with sub-micron precision,to a new generalized theoretical model that accounts for the nonlinear optical properties of TMDs.This enabled us to distinguish between different crystallographic domains,locate boundaries and reveal fine structure.As a consequence,we can calculate the mean orientational average of armchair angle distributions in specific regions of interest and define the corresponding standard deviation as a figure-of-merit for the 2D crystal quality.
