Conductivity Of Armchair Graphene Nanoribbons Research Articles

Gap parameter effect on thermal transport of doped armchair gapped graphene nanoribbon structure

We address the thermal conductivity of armchair graphene nanoribbon within tight binding model Hamiltonian. The possible effects of gap parameter, ribbon width and chemical potential on thermal conductivity are investigated. Green's function approach has been employed in order to calculate thermal conductivity of the system. We have also found the temperature dependence of the thermal conductivity for various ribbon widths and chemical potentials. Our results show a peak appears in temperature dependence of thermal conductivity for each value of chemical potential and ribbon width.

Magnetic Field Effects on Optical Conductivity of Doped Armchair Graphene Nanoribbon

We address the optical conductivity of armchair graphene nanoribbon within tight-binding model Hamiltonian using Green’s function approach. The possible effects of ribbon width, magnetic field, and chemical potential on optical absorption are investigated. We have also found the dependence of the optical conductivity for various ribbon widths and chemical potentials. Our results show a peak appears in the frequency dependence of optical conductivity of graphene nanoribbon. Upon increasing ribbon width, the height of the optical conductivity at frequency of peak increases. Also, applying the magnetic field causes an increase of the optical conductivity. However, upon more increase of the magnetic field leads to a decrease of the optical conductivity. Moreover, we study the effects of chemical potentials on frequency behavior of optical absorption of graphene nanoribbon for both metallic and insulator cases.

Electronic thermal conductivity of armchair graphene nanoribbons and zigzag carbon nanotubes

Through the Green's function formalism and tight-binding Hamiltonian model calculations, the temperature dependent electronic thermal conductivity (TC) for different diameters of zigzag carbon nanotubes and their corresponding unzipped armchair graphene nanoribbons is calculated. All functional temperature dependencies bear crossovers, for which, at higher temperatures, nanotubes have a slightly higher TC than their derived nanoribbons, while below that crossover, both systems exhibit a significant coincidence over a moderate range of lower temperatures. Noticeably, TC decreases with increasing the width or diameter of the corresponding systems. Also, at low temperatures TC is proportional to the density of states around the Fermi level, and thus increasing for metal or semiconductors of narrower gap cases.

Electronic heat capacity and thermal conductivity of armchair graphene nanoribbons

Using the Green’s function formalism and tight-binding Hamiltonian model in the band representation, for various widths of armchair graphene nanoribbons, the band structure, density of states, and temperature dependence of the heat capacity and thermal conductivity are considered for the electronic contribution per single width of the ribbons. Observed for various widths are similar peaks of Schottky anomaly, but with a tiny departure toward higher temperatures and a slight decline (rise) before (after) it for wider ribbons. Furthermore, the thermal conductivity decreases as the width of the ribbon gets larger, owing to the overlap between the nonhybridized \(p_{z}\) orbitals which provide literal paths across the ribbon to distract a part of the electron’s drift from the axial direction.

Concentration Effects of Carbon Oxides on Sensing by Graphene Nanoribbons: Ab Initio Modeling

We study detection of CO and CO2 gas molecules by change in quantum conductance of armchair graphene nanoribbons (AGNR) with a width of ∼1 nm. Quantum conductance modulations are calculated by using the second-order Møller–Plesset (MP2) method and density functional theory (DFT) for geometry optimization and a hybrid approach for electronic structure calculations. We determine stable and metastable physisorption orientations of gas molecules with varying concentrations. Our MP2-calculated binding energies relate 8.33% and 16.33% surface coverages of CO and CO2, respectively, to 1.72 × 104 and 497 ppm. With such concentrations, adsorption of molecules results in conductance characteristics shifts on the order of few meV. As the concentrations detected in experiments are much less, other mechanisms including substrate and/or carrier gas doping as well as adsorption on defects or electrodes may contribute toward gas sensing using graphene plates. We also discuss temperature effects and propose possible methods for improving gas detection by GNRs.

Effect of vacancy defects on the thermal conductivity of graphene nanoribbons: a molecular dynamics study

The reverse non-equilibrium molecular dynamics (RNEMD) has been performed to compute the thermal conductivity of armchair graphene nanoribbons (AGNRS) affected by vacancy defects. One- and two-atom vacancy defects are observed on the thermal conductivity of AGNRS. We find that one-atom vacancy defects can decrease the thermal conductivity significantly. Two-atom vacancy defects are located along the axial direction of AGNRS, and the thermal conductivity drops with the number of atoms between two-atom vacancies defects increasing. When two-atom vacancy defects are located along the longitudinal direction of AGNRS, the reduction of the thermal conductivity of AGNRS shows a pan shape.