Conductivity engineering of graphene by defect formation
S. H. M. Jafri, Karel Carva, Erika Widenkvist, Tobias Blom, Biplab Sanyal, Jonas Fransson, Olle Eriksson, Ulf Jansson, Helena Grennberg, Olof Karis, R. Quinlan,… 展开作者
S. H. M. Jafri, Karel Carva, Erika Widenkvist, Tobias Blom, Biplab Sanyal, Jonas Fransson, Olle Eriksson, Ulf Jansson, Helena Grennberg, Olof Karis, R. Quinlan, B. C. Holloway, Klaus leifer
备注：
8 pages, 8 figures
发表信息：
S H M Jafri et al 2010 J. Phys. D: Appl. Phys. 43 045404 (8pp)
Transport measurements have revealed several exotic electronic properties of graphene. The possibility to influence the electronic structure and hence control the conductivity by adsorption or doping with adatoms is crucial in view of electronics applications. Here, we show that in contrast to expectation, the conductivity of graphene increases with increasing concentration of vacancy defects, by more than one order of magnitude. We obtain a pronounced enhancement of the conductivity after insertion of defects by both quantum mechanical transport calculations as well as experimental studies of carbon nano-sheets. Our finding is attributed to the defect induced mid-gap states, which create a region exhibiting metallic behavior around the vacancy defects. The modification of the conductivity of graphene by the implementation of stable defects is crucial for the creation of electronic junctions in graphene-based electronics devices.
Declining the lattice thermal conductivity in graphene is essential for its thermoelectric applications. In high electron density systems, scatterings of phonons by electrons are no less than the phonon scatterings by other phonons. With the aid of first-principle calculations we examine the lattice thermal conductivity in graphene by inducing electron-phonon scattering externally. With experimentally tunable charge carrier density we find $\sim 50\%$ reduction of the lattice thermal conductivity at 200 K. The present study opens up new avenues for potential thermoelectric applications of grap…
The extremely high thermal conductivity of graphene has received great attention both in experiments and calculations. Obviously, new feature in thermal properties is of primary importance for application of graphene-based materials in thermal management in nanoscale. Here, we studied the thermal conductivity of graphene helicoid, a newly reported graphene-related nanostructure, using molecular dynamics simulation. Interestingly, in contrast to the converged cross-plane thermal conductivity in multi-layer graphene, axial thermal conductivity of graphene helicoid keeps increasing with thickness…
In this paper, the effect of B and N doping on the phonon induced thermal conductivity of graphene has been investigated. This study is important when one has to evaluate the usefulness of electronic properties of B and N doped graphene. We have performed the calculations by employing density functional perturbation theory(DFPT) to calculate the inter-atomic forces=force constants of pristine/doped graphene. Thermal conductivity calculations have been carried out by making use of linearized Boltzmann transport equations (LBTE) under single-mode relaxation time approximation (RTA). The thermal …
Prior ultralow thermal conductivity materials are not suitable for thermoelectric applications due to the limited electronic transport in the materials. Here, we present a new class of ultralow thermal conductivity materials with substantial electronic heat transport. Our samples are graphene/metal heterostructures of transferred graphene and ultrathin metal films (Pd, Au and Ni) deposited by either thermal evaporation or rf magnetron sputtering. For the evaporated samples, we achieve an ultralow thermal conductivity of 0.06 W m-1 K-1, with phonons as the dominant heat carriers. The ultralow t…
A recently derived formula for complex conductivity of the monolayer graphene is analyzed. We show that the real and imaginary parts in this formula obey the Kramers and Kronig dispersion relations which are a good test for validity of the formula for complex conductivity of monolayer graphene. We consider also an additional test for this formula, sensitive to the integral characteristic of the conductance such as the famous f sum rule. We write it in the two dimensional form and show that it fulfils identically if we admit the cyclotron mass as an effective one and take the principal value of…
We investigate the electronic transport properties of copper-graphene composites using a density-functional framework. Conduction in composites by varying the interface distance of a copper/graphene/copper (Cu/G/Cu) interface models was studied. The electronic density of states reveals increasing contributions from both copper and carbon atoms near the Fermi level with decreasing Cu-G interfacial distance. Electronic conductivity of the models computed using the Kubo-Greenwood formula showed the conductivity increases with decreasing Cu-G distance. We also find that the conductivity saturates …
Although defects on graphene can degrade electron transport and its ability for use as a protection layer, they can also be helpful to tailor the local properties or activate new sites for particular adsorbates. Here, carbon vacancy defects are formed in graphene films on Ru(0001) using low energy Ar$^+$ bombardment and the materials are then reacted at room temperature with oxygen (O$_2$). Helium low energy ion scattering shows that no oxygen attaches to the intact graphene layer. When isolated single carbon vacancy defects are present, oxygen adsorbs molecularly at the defect sites and inter…
In this work, we demonstrate that edge-oxidation of graphene can enable larger enhancement in thermal conductivity (k) of graphene-nanoplatelet (GnP)/polyetherimide (PEI) composites relative to oxidation of the basal plane of graphene. Edge oxidation (EGO) offers the advantage of leaving the basal plane of graphene intact, preserving its high in-plane thermal conductivity (kin > 2000 Wm-1K-1), while, simultaneously, the oxygen groups introduced on graphene edge enhance interfacial thermal conductance through hydrogen bonding with oxygen groups of polyetherimide (PEI), enhancing overall polymer…
We consider the Zitterbewegung of Dirac electrons in the monolayer graphene as the nonrelativistic analog of the phenomenon predicted by E. Schrödinger for the relativistic electrons in the free space. So we show that the Dirac electrons of monolayer graphene oscillate, i.e. produce fast fluctuation of an electron position around the mean value with rather high frequency but much less than the relativistic electrons in the free space. We also study relation between the Zitterbewegung of the conductivity electrons wave packet formed by the Fermi-Dirac distribution and the high-frequency complex…
