Abstract:We propose a useful metallic field effect element based on the electric field control of armchair single-wall carbon nanotube. The electron conduction channels are enhanced by imposing a transverse gate voltage. Multiple Dirac points have been revealed theoretically by our density functional and tight binding calculations. Our electron transport results show that the performance of such unique transistors depends mainly on the diameter of nanotube exploited. The critical field strength required decreases rapid… Show more
“…For example, Zhang et al have observed experimentally that the longitudinal electronic transport of ZnO nanowires can be tuned by the transverse electric field. 5 On the other hand, it has been extensively proved theoretically that the electric field can efficiently modulate the electronic properties in numerous nanostructures, such as carbon NTs, [6][7][8][9][10][11] BN NTs, [12][13][14] SiC NTs, 15 GaN NWs and NTs, 16 Si NWs, 17 AlN nanoribbons, 18 and ZnO nanoribbons. 19 For instance, Yilmaz et al 16 have observed the transverse electric field can induce a homojunction across the diameter for the GaN NTs and NWs.…”
Using the density functional theory, we investigate the electronic properties of ZnO nanowires (NWs) and faceted nanotubes (NTs) under a transverse electric field. We find that the band gap of ZnO nanostructures tends to decrease as the electric field is increased, and the variation of the band gap is dependent upon the diameter and wall thickness. Furthermore, the applied electric field could induce semiconductor-metal transition and enhance the electron effective mass. These results provide a valuable guide for the future application of ZnO nanostructures in the field of microelectronic and optoelectronic materials and nanodevices.
“…For example, Zhang et al have observed experimentally that the longitudinal electronic transport of ZnO nanowires can be tuned by the transverse electric field. 5 On the other hand, it has been extensively proved theoretically that the electric field can efficiently modulate the electronic properties in numerous nanostructures, such as carbon NTs, [6][7][8][9][10][11] BN NTs, [12][13][14] SiC NTs, 15 GaN NWs and NTs, 16 Si NWs, 17 AlN nanoribbons, 18 and ZnO nanoribbons. 19 For instance, Yilmaz et al 16 have observed the transverse electric field can induce a homojunction across the diameter for the GaN NTs and NWs.…”
Using the density functional theory, we investigate the electronic properties of ZnO nanowires (NWs) and faceted nanotubes (NTs) under a transverse electric field. We find that the band gap of ZnO nanostructures tends to decrease as the electric field is increased, and the variation of the band gap is dependent upon the diameter and wall thickness. Furthermore, the applied electric field could induce semiconductor-metal transition and enhance the electron effective mass. These results provide a valuable guide for the future application of ZnO nanostructures in the field of microelectronic and optoelectronic materials and nanodevices.
“…10 However temperature introduces atomic displacements and significant backscattering for electronic states far away from the Fermi level E f while having only minimal effects on the linear bands crossing at E f . This effect roots in the fact that only two bands of different symmetries contribute to transport near Fermi level, 17 and the special topological properties of the dispersion near the Dirac point protects the system from backscattering between one band and the other at the same K point. Although K → KЈ backscattering is allowed, the long-range atomic displacement due to phonons is very insufficient in causing such large momentum transitions.…”
We consider the effect of thermal phonon displacements on the coherent transport in carbon nanotubes. The atomic displacements are generated using tight-binding molecular dynamics simulations, and the conductances are computed using a nonequilibrium Green's function technique. Atomic displacements due to lattice vibrations lead to different levels of conductance reduction and fluctuation on the massive and massless bands of a metallic nanotube. Different conduction regimes are studied by examining the resistance on different length scales. The temperature-induced displacements have a significant impact on the ballistic or diffusive transport in carbon nanotube. DOI: 10.1103/PhysRevB.79.161404 PACS number͑s͒: 73.63.Ϫb, 63.22.Ϫm, 65.80.ϩn Resistive heating is expected to be a severe problem when the miniaturization of electronic components reaches the ultimate limit of the nanoscale. Such an overheating effect is unavoidable for nanowire made of the ordinary metals or III-V semiconductors. As a potentially ballistic conductor, 1 carbon nanotubes seem to offer a unique alternative conducting wires and elements. This is a result of their peculiar band dispersion and absence of surface scattering for conduction electrons. On the other hand, there must be a transition from ballistic to diffusive transport and eventually to localization behavior in a one-dimensional system when disorder sets in. The question is about the length of the tube and the amount of disorder that will make such transitions observable. We present results of electron transport for carbon nanotube segments of different lengths in the presence of different amount of atomic position disorder, owing to the finite temperatureinduced lattice vibrations. The atomic displacements are generated using the tight-binding molecular dynamics ͑TBMD͒. The impact of lattice distortions on the charge transport is captured by the configurational averaging statistics. In this scheme, electron-phonon interactions for a large number of vibrational modes in realistic nanotubes need not be directly calculated. 2 In contrast, so far calculations of electronphonon matrix element calculations have been limited to study periodic nanotube or small molecular systems. 3 The model structure is an armchair metallic ͑6,6͒ nanotube which consists of 576 carbon atoms in the scattering region ͑d ϳ 60 Å in length͒. To better deal with the low frequency acoustic and optical phonon modes an even longer tube supercell could be considered, although that makes our computation more expensive. First, we run TBMD ͑Ref. 4͒ at 100, 300, and 700 K, where the temperature has been rescaled to take zero point motion into account. The details of the TBMD method can be found elsewhere. 5,6 The advantage of the TBMD approach is that it incorporates the electronic effects into molecular dynamics ͑MD͒ through an environment-dependent tight-binding Hamiltonian, 7,8 with parameters fitted to a very broad data generated by firstprinciples calculations. We have calculated some phonon frequencies of dia...
“…In other words, the intrinsic electric field provided by electronegativity difference between hydrogen and fluorine at opposite sides of bismuth in Bi 2 HF nanosheet induces the band gap opening. The physical mechanism is similar to the situation of bilayer graphene 40 , 41 and other low dimensional materials 42 , 43 under the external electric field. Figure 2 The electronic structure of Bi 2 HF nanosheet.…”
Spin-valley and electronic band topological properties have been extensively explored in quantum material science, yet their coexistence has rarely been realized in stoichiometric two-dimensional (2D) materials. We theoretically predict the quantum spin Hall effect (QSHE) in the hydrofluorinated bismuth (Bi2HF) nanosheet where the hydrogen (H) and fluorine (F) atoms are functionalized on opposite sides of bismuth (Bi) atomic monolayer. Such Bi2HF nanosheet is found to be a 2D topological insulator with a giant band gap of 0.97 eV which might host room temperature QSHE. The atomistic structure of Bi2HF nanosheet is noncentrosymmetric and the spontaneous polarization arises from the hydrofluorinated morphology. The phonon spectrum and ab initio molecular dynamic (AIMD) calculations reveal that the proposed Bi2HF nanosheet is dynamically and thermally stable. The inversion symmetry breaking together with spin-orbit coupling (SOC) leads to the coupling between spin and valley in Bi2HF nanosheet. The emerging valley-dependent properties and the interplay between intrinsic dipole and SOC are investigated using first-principles calculations combined with an effective Hamiltonian model. The topological invariant of the Bi2HF nanosheet is confirmed by using Wilson loop method and the calculated helical metallic edge states are shown to host QSHE. The Bi2HF nanosheet is therefore a promising platform to realize room temperature QSHE and valley spintronics.
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