Article

Graphene nanoflakes - structural and electronic properties

Physical Review B (Impact Factor: 2.66). 02/2013; 81:085430. DOI: 10.1103/PhysRevB.81.085430
Source: arXiv

ABSTRACT The structures, cohesive energies and HOMO-LUMO gaps of graphene nanoflakes
and corresponding polycyclic aromatic hydrocarbons for a large variety of size
and topology are investigated at the density functional based tight-binding
level. Polyacene-like and honeycomb-like graphene nanoflakes were chosen as the
topological limit structures. The influence of unsaturated edge atoms and
dangling bonds on the stability is discussed. Our survey shows a linear trend
for the cohesive energy as function of Ns/N (N - total number of atoms and Ns
is number of edge atoms). For the HOMO-LUMO gap the trends are more complex and
include also the topology of the edges.

1 Bookmark
 · 
254 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Density-functional tight-binding and classical molecular dynamics simulations are used to investigate the structural deformations and melting of planar carbon nano-clusters $C_{N}$ with N=2-55. The minimum energy configurations for different clusters are used as starting configuration for the study of the temperature effects on the bond breaking/rotation in carbon lines (N$<$6), carbon rings (5$<$N$<$19) and graphene nano-flakes. The larger the rings (graphene nano-flake) the higher the transition temperature (melting point) with ring-to-line (perfect-to-defective) transition structures. The melting point was obtained by using the bond energy, the Lindemann criteria, and the specific heat. We found that hydrogen-passivated graphene nano-flakes (C$_{N}$H$_M$) have a larger melting temperature with a much smaller dependence on its size. The edges in the graphene nano-flakes exhibit several different meta-stable configurations (isomers) during heating before melting occurs.
    Physical Review B 04/2013; 87(13). · 2.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We investigate quantum transport properties of triangular graphene flakes with zigzag edges by using first principles calculations. Triangular graphene flakes have large magnetic moments which vary with the number of hydrogen atoms terminating its edge atoms and scale with its size. Electronic transmission and current-voltage characteristics of these flakes, when contacted with metallic electrodes, reveal spin valve and remarkable rectification features. The transition from ferromagnetic to antiferromagnetic state under bias voltage can, however, terminate the spin polarizing effects for specific flakes. Geometry and size dependent transport properties of graphene flakes may be crucial for spintronic nanodevice applications. Comment: 5 pages, 4 Figures
    Journal of Applied Physics 10/2010; · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Boron and nitrogen substitutional impurities in graphene are analyzed using a self-consistent tight-binding approach. An analytical result for the impurity Green's function is derived taking broken electron-hole symmetry into account and validated by comparison to numerical diagonalization. The impurity potential depends sensitively on the impurity occupancy, leading to a self-consistency requirement. We solve this problem using the impurity Green's function and determine the self-consistent local density of states at the impurity site and, thereby, identify acceptor and donor energy resonances.
    Physical review. B, Condensed matter 04/2013; 87(15). · 3.77 Impact Factor

Full-text (2 Sources)

View
100 Downloads
Available from
May 27, 2014