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1.
《Current Applied Physics》2001,1(1):39-44
The electrical properties of single-wall C, BN, and BC3 nanotubes in ideally rolled-up forms show a wide spectrum from truly metals to large band gap semiconductors. In the presence of radial deformations that collapse tubes, the electrical properties are severely modified such that metals turn into semiconductors and vice versa. Based on first-principles pseudopotential calculations, we find that metallic C nanotubes have a finite band gap if radial deformations break all mirror symmetries of the tubes, and that original finite gaps (∼0.5 eV) of semiconducting C and BC3 tubes are closed by collapsing deformations. In BN tubes, band gaps can be tuned in the range 2–5 eV. On the other hand, the band gaps of armchair BN and zigzag BC3 nanotubes are found to be insensitive to radial deformations. These new findings can be applied to design new types of nanotube-based functional devices using radial deformations. 相似文献
2.
S. V. Lisenkov G. A. Vinogradov T. Yu. Astakhova N. G. Lebedev 《Physics of the Solid State》2006,48(1):192-198
Planar and nanotubular structures that are based on boron and nitrogen and consist of tetragons, hexagons, and octagons are
considered. By analogy with carbon nanoobjects of the same topology, these structures are referred to as Haeckelites. The
geometric, electronic, and energy properties are thoroughly investigated for two variants of the regular mutual arrangement
of the polygons. It is established that planar and nanotubular BN structures of the Haeckelite type are dielectrics with a
band gap E
g ∼ 3.2–4.2 eV, which is less than the band gap E
g for BN nanotubes consisting only of hexagons. The cohesive energy of the BN nanotubes under investigation exceeds the cohesive
energy of BN hexagonal nanotubes by 0.3 eV/atom. 相似文献
3.
Encapsulation of fullerene into nanotubes based on a C2N sheet, known as nitrogenated holey graphene, was investigated using density functional theory. The structural and electronic properties of these carbon hybrid materials, consisting of nitrogenated holey nanotubes and a small C20 fullerene, were studied. The formation energies showed that encapsulation of the fullerene into the nitrogenated holey nanotube is an exothermic process. To characterise the electronic properties, the electronic band structure and density of states of armchair and zigzag nitrogenated holey nanotubes were calculated. Filling these nanotubes with the C20 fullerene resulted in a p-type semiconducting character. The energy band gap of the nitrogenated holey nanotubes decreased with fullerene encapsulation. The results are indicative of the possibility of band gap engineering by encapsulation of small fullerenes into nitrogenated holey nanotubes. 相似文献
4.
N. Zibouche A. Kuc T. Heine 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(1):49
MoS2 and WS2 layered transition-metal dichalcogenides are indirect
band gap semiconductors in their bulk forms. Thinned to a monolayer, they undergo a
transition and become direct band gap materials. Layered structures of that kind can be
folded to form nanotubes. We present here the electronic structure comparison between
bulk, monolayered and tubular forms of transition metal disulfides using first-principle
calculations. Our results show that armchair nanotubes remain indirect gap semiconductors,
similar to the bulk system, while the zigzag nanotubes, like monolayers, are direct gap
materials, what suggests interesting potential applications in optoelectronics. 相似文献
5.
The structure stability, magnetic, electronic, optical, and photocatalytic properties of nonmetal (B, C, N, P, and S), and halogen (F, Cl, Br, and I)-doped anatase TiO2 nanotubes (TNTs) have been investigated using spin polarized density functional theory. The N- and F-doped TNTs are the most stable among other doped TNTs. It is found that the magnetic moment of doped TNT is the difference between the number of the valence electrons of the dopant and host anion. All dopants decrease the band gap of TNT. The decrease in the band gap of nonmetal (C, N, P, and S)-doped TNTs, in particular N and P, is larger than that of halogen-doped TNTs due to the created states of the nonmetal dopant in the band gap. There is a good agreement between the calculation results and the experimental observations. Even though C-, N-, and P-doped TNTs have the lowest band gap, they cannot be used as a photocatalysis for water splitting. The B-, S-, and I-doped TiO2 nanotubes are of great potential as candidates for water splitting in the visible light range. 相似文献
6.
The structure of a new non-carbon (beryllium oxide BeO) nanotube consisting of a rolled-up graphene sheet is proposed, and its physical properties are described. Ab initio calculations of the binding energy, the electronic band structure, the density of states, the dependence of the strain energy of the nanotube on the nanotube diameter D, and the Young’s modulus Y for BeO nanotubes of different diameters are performed in the framework of the density functional theory (DFT). From a comparison of the binding energies calculated for BeO nanotubes and crystalline BeO with a wurtzite structure, it is inferred that BeO nanotubes can be synthesized by a plasma-chemical reaction or through chemical vapor deposition. It is established that BeO nanotubes are polar dielectrics with a band gap of ~5.0 eV and a stiffness comparable to that of the carbon nanotubes (the Young’s modulus of the BeO nanotubes Y BeO is approximately equal to 0.7Y C, where Y C is the Young’s modulus of the carbon nanotubes). It is shown that, for a nanotube diameter D > 1 nm, the (n, n) armchair nanotubes are energetically more favorable than the (n, 0) zigzag nanotubes. 相似文献
7.
It is demonstrated that the CK α x-ray fluorescence spectra of carbon nanotubes synthesized by electric-arc evaporation of graphite and the spectra of carbon nanotubes produced using catalytic decomposition of hydrocarbons differ in the intensity of the short-wavelength lines. In order to interpret the obtained data, the electronic structures of perfect and defect-containing nanotubes are calculated in the framework of the tight-binding method with optimized parameters. The density of localized states that correspond to the observed increase in the intensity of the fluorescence spectrum of catalytic nanotubes can be obtained in the case when 15–20% of the total number of carbon atoms are absent in the carbon network. It is shown that defects of this type can bring about a decrease in the band gap of the nanotubes. 相似文献
8.
The stability and electronic structure of hypothetical InN nanotubes were
studied by first-principles density functional theory. It was found that the
strain energies of InN nanotubes are smaller than those of carbon nanotubes
of the same radius. Single-wall zigzag InN nanotubes were found to be
semiconductors with a direct band gap while the armchair counterparts
have an indirect band gap. The band gaps of nanotubes decrease with
increasing diameter,
similar to the case of carbon nanotubes. 相似文献
9.
A new class of non-carbon nanotubes based on Group III and Group V elements (aluminum and phosphorus, respectively) is considered. The equilibrium geometry, energy characteristics, and electronic structure of the AlP nanotubes were calculated using the density functional theory. These calculations demonstrated that the AlP nanotubes are energetically stable structures. It was found that a low strain energy (approximately 0.01–0.07 eV) is required for rolling a two-dimensional hexagonal AlP structure into a tube. The AlP nanotubes are found to be wide-band-gap semiconductors with a band gap of 2.05–3.73 eV with direct (for the zigzag type) or indirect (for the armchair type) transitions between the top of the valence band and the bottom of the conduction band. The band gap of these nanotubes increases with the tube diameter, approaching the band gap of a two-dimensional hexagonal AlP layer. 相似文献
10.
P.N. D’yachkov 《Journal of Physics and Chemistry of Solids》2009,70(1):180-185
The effect of intrinsic defects and isoelectronic substitutional impurities on the electronic structure of boron-nitride (BN) nanotubes is investigated using a linearized augmented cylindrical wave method and the local density functional and muffin-tin approximations for the electron potential. In this method, the electronic spectrum of a system is governed by a free movement of electrons in the interatomic space between cylindrical barriers and by a scattering of electrons from the atomic centers. Nanotubes with extended defects of substitution NB of a boron atom by a nitrogen atom and, vice versa, nitrogen by boron BN with one defect per one, two, and three unit cells are considered. It is shown that the presence of such defects significantly affects the band structure of the BN nanotubes. A defect band π(B, N) is formed in the optical gap, which reduces the width of the gap. The presence of impurities also affects the valence band: the widths of s, sp, and pπ bands change and the gap between s and sp bands is partially filled. A partial substitution of the N by P atoms leads to a decrease in the energy gap, to a separation of the Ds(P) band from the high-energy region of the s(B, N) band, as well as to the formation of the impurity Dπ(P) and Dπ*(P) bands, which form the valence-band top and conduction-band bottom in the doped system. The influence of partial substitution of N atoms by the As atom on the electronic structure of BN nanotubes is qualitatively similar to the case of phosphorus, but the optical gap becomes smaller. The optical gap of the BN tubule is virtually closed due to the effect of one Sb atom impurity per translational unit cell, in contrast to the weak indium-induced perturbation of the band structure of the BN nanotube. Introduction of the one In, Ga or Al atom per three unit cells of the (5, 5) BN nanotube results in 0.6 eV increase of the optical gap. The above effects can be detected by optical and photoelectron spectroscopy methods, as well as by measuring electrical properties of the pure and doped BN nanotubes. They can be used to design electronic devices based on BN nanotubes. 相似文献
11.
Structural and electronic properties of composite BxCyNz nanotubes and heterojunctions 总被引:1,自引:0,他引:1
X. Blase J.-C. Charlier A. De Vita R. Car 《Applied Physics A: Materials Science & Processing》1999,68(3):293-300
x CyNz nanotubes and related heterojunctions have been studied using both ab initio and semi-empirical approaches. Pure BN nanotubes
present a very stable quasiparticle band gap around 5.5–6.0 eV independent of the tube radius and helicity. The bottom of
the conduction bands is controlled by a nearly-free-electronn state localized inside the nanotube, suggesting interesting
properties under doping. In the case of nanotubes with BC2N stoichiometry, we show that in the thermodynamic limit the system is driven towards segregation of pure C and BN sections.
This demixing significantly affects the electronic properties of such materials. The same process of segregation into BC3 islands is evidenced in the case of B-doped carbon nanotubes. These spontaneous segregation processes lead to the formation
of quantum dots or nanotube heterojunctions. In particular, C/BN superlattices or isolated junctions have been investigated
as specific examples of the wide variety of electronic devices that can be realized using such nanotubes.
Received: 27 November 1998 / Accepted: 14 December 1998 相似文献
12.
First-principles study of nanotubes within the tetragonal,hexagonal and dodecagonal cycle structures
A systematic study has been done on the structural and electronic properties of carbon, boron nitride and aluminum nitride nanotubes with structure consisting of periodically distributed tetragonal (T ≡A2X2), hexagonal (H ≡A3X3) and dodecagonal (D ≡A6X6) (AX=C2, BN, AlN) cycles. The method has been performed using first-principles calculations based on density functional theory (DFT). The optimized lattice parameters, density of state (DOS) curves and band structure of THD-NTs are obtained for (3, 0) and (0, 2) types. Our calculation results indicate that carbon nanotubes of these types (THD-CNTs) behave as a metallic, but the boron nitride nanotubes (THD-BNNTs) (with a band gap of around 4 eV) as well as aluminum nitride nanotubes (THD-AlNNTs) (with a band gap of around 2.6 eV) behave as an semiconductor. The inequality in number of atoms in different directions is affected on structures and diameters of nanotubes and their walls curvature. 相似文献
13.
We present in this review a joint experimental and theoretical overview of the synthesis techniques and properties of boron-nitride (BN) and boron-carbonitride (BCN) nanotubes. While their tubular structure is similar to that of their carbon analogues, we show that their electronic properties are significantly different. BN tubes are wide band gap insulators while BCN systems can be semiconductors with a band gap in the visible range. 相似文献
14.
15.
Caifeng Ge Xiaowei Li Jinming Dong 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):105-110
The vibrational properties and the band gaps of new B2C nanotubes have been studied by the first principles calculations. It is found that (1) there is a typical Raman-active radial-breathing vibrational mode (RBM), which is similar to that of carbon nanotubes. The RBM frequency decreases in a linear proportion to the inverse diameter, whose variation slope depends on the types of B2C nanotubes. (2) Under an applied tensile strain, the band gap of B2C tubes is found to change greatly. For example, their band gaps can decrease to zero with increasing tensile strain for the (n, 0) B2C tubes with odd n, showing clearly a metal–insulator transition, which cannot happen for the (n, 0) B2C tubes with even n and the (0, n) B2C tubes. 相似文献
16.
Hybrid transition-metal dichalcogenides(TMDs) with different chalcogens on each side(X-TM-Y) have attracted attention because of their unique properties. Nanotubes based on hybrid TMD materials have advantages in flexibility over conventional TMD nanotubes. Here we predict the wide band gap tunability of hybrid TMD double-wall nanotubes(DWNTs) from metal to semiconductor. Using density-function theory(DFT) with HSE06 hybrid functional, we find that the electronic property of X-Mo-Y DWNTs(X = O and S, inside a tube; Y = S and Se, outside a tube) depends both on electronegativity difference and diameter difference. If there is no difference in electron negativity between inner atoms(X) of outer tube and outer atoms(Y) of inner tube, the band gap of DWNTs is the same as that of the inner one. If there is a significant electronegativity difference, the electronic property of the DWNTs ranges from metallic to semiconducting, depending on the diameter differences. Our results provide alternative ways for the band gap engineering of TMD nanotubes. 相似文献
17.
We studied the structural and electronic properties of carbon
nanotubes under hydrostatic pressures based on molecular dynamics
simulations and first principles band structure calculations. It is
found that carbon nanotubes experience a hard-to-soft transition as
external pressure increases. The bulk modulus of soft phase is two
orders of magnitude smaller than that of hard phase. The band
structure calculations show that band gap of (10, 0) nanotube
increases with the increase of pressure at low pressures. Above a
critical pressure (5.70GPa), band gap of (10, 0) nanotube drops
rapidly and becomes zero at 6.62GPa. Moreover, the calculated charge
density shows that a large pressure can induce an
{sp}2-to-{sp}3 bonding transition, which is confirmed by
recent experiments on deformed carbon nanotubes. 相似文献
18.
Z. HeH.Y. He 《Applied Surface Science》2011,258(2):972-976
Nano N-doped TiO2 nanotubes were fabricated by hydrothermally treating N-doped TiO2 nanorods in a 8 M NaOH solution at 110 °C for 20 h. The N-doped TiO2 nanorods were synthesized by a solvothermal process with precursor solution containing titanium sulfate, urea, and dichloroethane. The N-doped TiO2 nanorods and nanotubes were characterized with X-ray diffraction, transmission electron microscopy, and UV-vis spectrophotometry. The nitrogen contents of the N-doped TiO2 nanorods and nanotubes were reached to high values of 36.9 at.% and 25.7 at.%, respectively. The nitrogen doping narrowed the band gap of the N-doped TiO2 nanorods and nanotubes and introduced indirect band gap to the powders, which respectively extended the absorption edge to visible light and infrared region. The nanotubes showed larger specific surface area and greater degradation efficiency to methyl orange than the nanorods. 相似文献
19.
Zekan Qian Shimin Hou Jiaxing Zhang Rui Li Ziyong Shen Xingyu Zhao Zengquan Xue 《Physica E: Low-dimensional Systems and Nanostructures》2005,30(1-2):81-85
Based on density functional theory calculations, we predict the stability and electronic structures of single-walled indium nitride (InN) nanotubes. Compared with other group III-nitride nanotubes with a similar diameter, strain energies of InN nanotubes relative to their graphitic sheet are the lowest, suggesting the possibility of the formation of InN nanotubes. Considering the stability of a graphitic InN sheet, InN nanotubes are in metastable states with the stability between GaN nanotubes and AlN nanotubes. Contrary to the case of carbon nanotubes and BN nanotubes, the bond-length of both horizontal and vertical In–N bonds in InN nanotubes decreases as the tube diameter increases. InN nanotubes are all semiconductors with an almost constant band gap of about 1 eV. The existence of a direct gap in zigzag InN nanotubes and the small band gap indicate that they may have potential applications in light emitting devices and solar cells. 相似文献
20.
Binary Si: H alloy films having a wide optical band gap have been prepared by r.f. glow discharge of disilane. The optical band gap and the infrared absorption spectrum have been measured for those binary alloy films. The infrared absorption strength for 850 cm-1 peak and the vibrational freqcencies for all absorption peaks are increased with an increase in the optical band gap. This sugests the (SiH2)n group formation in a wide optical gap film. 相似文献