Electro-optical properties of single-walled carbon nanotubes (original) (raw)

Optoelectronic Properties of Single-Wall Carbon Nanotubes

Advanced Materials, 2012

diffraction is a powerful technique for the determination of atomic structure of individual nano-objects, as was demonstrated in Iijima's original work on multiwall [ 187 ] and singlewall [ 1 ] carbon nanotubes. However, it is not suited for studying a large number of carbon nanotubes. Therefore, optical spectroscopy has emerged in the last decade as the most convenient means for determining the chirality indices (n , m) of SWCNTs in macroscopic ensembles of SWCNTs. There is now a wellestablished correlation between optical transition energies, diameters, and (n , m) indices, as shown in Figure 2 a. [ 188 ] RRS spectroscopy has served as the most commonly used tool for (n , m) determination for both metallic and semiconducting SWCNTs for many years. [ 189 ] For semiconducting, or ν = ± 1, SWCNTs, PLE spectroscopy [ 24-35 ] can provide accurate information on the E 11 and E 22 energies from the emission and excitation photon energies, respectively, as shown in Figure 2 b. One can also combine PLE and RRS spectroscopies to determine E 33 and E 44 in semiconducting nanotubes. [ 190 ] Furthermore, as detailed in Section 3, coherent phonon spectroscopy has several advantages for simultaneously determining (n , m) indices and phonon frequencies for both semiconducting and metallic SWCNTs (see Figure 2 c). Finally, Section 4 presents how aligned SWCNT fi lms can be used to develop optoelectronic devices, ranging from state-of-the-art terahertz polarizers to large-area, broadband photodetectors. 2. Enrichment and Spectroscopy of Armchair Carbon Nanotubes Because of their excellent electrical properties, metallic SWCNTs are considered to be promising candidates for a variety of future electronic applications such as nanocircuit interconnects and power transmission cables. In particular, (n , n)-chirality, or 'armchair,' metallic nanotubes are theoretically predicted to be truly gapless and intrinsically insensitive to disorder, [ 191-192 ] consistent with experimentally observed ballistic conduction behavior at the single-tube level. Unfortunately, progress towards creating such ballistic-conducting armchair devices in bulk quantities has been slowed by the inherent problem of nanotube synthesis, whereby both semiconducting and metallic nanotubes are produced. Sébastien Nanot received his Ph.D. from Université de Toulouse (France) in 2009 under supervision by Profs. Bertrand Raquet and Jean-Marc Broto. His thesis focused on individual carbon nanotube properties under a very high magnetic fi eld. He moved to Rice University where he is appointed as a postdoctoral researcher in Prof. Junichiro Kono's group. His current research focuses on optoelectronic properties of carbon nanotubes ensembles.

Optical absorption and electron energy loss spectra of single-walled carbon nanotubes

Computational Materials Science, 2010

We have carried out a first principles calculation on the electronic structure, dielectric function and energy loss spectra of single-walled carbon nanotubes (SWCNTs). Calculations of optical spectra have been performed under electric fields polarized both parallel and perpendicular with respect to the nanotube axis. Our results show that the dielectric function is strongly anisotropic and much larger for the applied electric field parallel than perpendicular to the tube axis. We have calculated first, second, and third optical transitions in several SWCNTs with different chiralities, diameters and lengths. It is revealed that the absorption spectra of 4 Å single-walled carbon nanotubes depend strongly on their chiralities, while the absorption spectra of nanotubes with large diameter hardly show any chirality dependence. The results show that unlike the optical absorption, the energy loss function of SWCNTs does not significantly depend on chirality and show weak anisotropy. It is also found that the energy loss function peaks for electric fields polarized both parallel and perpendicular to the tube axis happen almost at the same energies, but with rather difference amplitudes.

Plasmon excitations of single-wall carbon nanotubes

Physical Review B, 2008

Plasmon excitations in isolated single-wall carbon nanotubes are singled out in the optical spectra, and analyzed within density-functional tight-binding method and random-phase approximation. Full symmetry considerations, implemented in both approaches, stressed out that only helical quantum numbers are conserved in processes involving momentum transfer, i.e., only these quantum numbers can be unambiguously attributed to the plasmons. Energy of plasmon is about 5 eV and slightly decreases with diameter with no observable influence of chirality. Energy of + plasmon is between 20 and 21 eV, and is insensitive to nanotube geometry. Dispersion of the plasmon is mainly linear. Slope of dispersion curve increases with tube's translational period.

Optical properties of armchair (7, 7) single walled carbon nanotubes

AIP Advances, 2015

Full potential linearized augmented plane waves method with the generalized gradient approximation for the exchange-correlation potential was applied to calculate the optical properties of (7, 7) single walled carbon nanotubes. The both x and z directions of the incident photons were applied to estimate optical gaps, dielectric function, electron energy loss spectroscopies, optical conductivity, optical extinction, optical refractive index and optical absorption coefficient. The results predict that dielectric function, ε (ω), is anisotropic since it has higher peaks along z-direction than x-direction. The static optical refractive constant were calculated about 1.4 (z-direction) and 1.1 (x-direction). Moreover, the electron energy loss spectroscopy showed a sharp π electron plasmon peaks at about 6 eV and 5 eV for z and x-directions respectively. The calculated reflection spectra show that directions perpendicular to the tube axis have further optical reflection. Moreover, z-direction indicates higher peaks at absorption spectra in low range energies. Totally, increasing the diameter of armchair carbon nanotubes cause the optical band gap, static optical refractive constant and optical reflectivity to decrease. On the other hand, increasing the diameter cause the optical absorption and the optical conductivity to increase. Moreover, the sharp peaks being illustrated at optical spectrum are related to the 1D structure of CNTs which confirm the accuracy of the calculations.

Excitonic Effects and Optical Spectra of Single-Walled Carbon Nanotubes

Physical Review Letters, 2004

Many-electron effects often dramatically modify the properties of reduced dimensional systems. We report calculations, based on an ab initio many-electron Green's function approach, of electronhole interaction effects on the optical spectra of small-diameter single-walled carbon nanotubes. Excitonic effects qualitatively alter the optical spectra of both semiconducting and metallic tubes. Excitons are bound by ∼ 1 eV in the semiconducting (8,0) tube and by ∼ 100 meV in the metallic (3,3) tube. These large many-electron effects explain the discrepancies between previous theories and experiments.

Chirality effects in carbon nanotubes

Physical Review B, 2002

We consider chirality related effects in optical, photogalvanic and electrontransport properties of carbon nanotubes. We show that these properties of chiral nanotubes are determined by terms in the electron effective Hamiltonian describing the coupling between the electron wavevector along the tube principal axis and the orbital momentum around the tube circumference. We develop a theory of photogalvanic effects and a theory of dc electric current, which is linear in the magnetic field and quadratic in the bias voltage. Moreover, we present analytic estimations for the natural circular dichroism and magneto-spatial effect in the light absorption.

Ab initio calculations of optical spectra of a chiral (4,1) carbon nanotube

Physica Status Solidi B-basic Solid State Physics, 2010

We report ab initio calculations of electronic and the linear optical properties of a (4,1) chiral carbon nanotube, using the full-potential linear augmented plane-wave (FP-LAPW) method. The dielectric tensor is derived within the randomphase approximation (RPA). All optical spectra, such as: dielectric function, absorption coefficient, optical conductivity, extinction coefficient, loss function, sum rule, reflectivity, and the refractive index have been calculated for both electric field polarizations, parallel and perpendicular to the tube axis. It is revealed that the optical spectra are anisotropic along these two polarizations. For the parallel polarization, adding the intraband transition contributions, will change the optical spectra of a (4,1) nanotube significantly. The calculated optical gap, E g , electronic dielectric constant, e(1), and the refractive index, n, in the parallel polarization are obtained as 2.6 eV, 1.98, and 1.4, respectively. The results show that for small diameter of SWCNTs the chirality has a strong effect on their optical spectra. Adding the intraband transition contributions showed that the dielectric function has singularity at zero frequency, due to the metallic behavior of a (4,1) chiral nanotube.

Chirality effects on an electron transport in single-walled carbon nanotube

Scientific Reports, 2020

In our work, we investigate characteristics of conductivity for single-walled carbon nanotubes caused by spin–orbit interaction. In the case study of chirality indexes, we especially research on the three types of single-walled carbon nanotubes which are the zigzag, the chiral, and the armchair. The mathematical analysis employed for our works is the Green-Kubo Method. For the theoretical results of our work, we discover that the chirality of single-walled carbon nanotubes impacts the interaction leading to the spin polarization of conductivity. We acknowledge such asymmetry characteristics by calculating the longitudinal current–current correlation function difference between a positive and negative wave vector in which there is the typical chiral-dependent. We also find out that the temperature and the frequency of electrons affect the function producing the different characteristics of the conductivity. From particular simulations, we obtain that the correlation decrease when the...