First-principles investigation on the electronic efficiency and binding energy of the contacts
formed by graphene and poly-aromatic hydrocarbon anchoring groups
Yang Li1, Xingcheng Tu1, Hao Wang1, Stefano Sanvito2, Shimin Hou1,*
1 Centre for Nanoscale Science and Technology, Key Laboratory for the Physics and Chemistry
of Nanodevices, Department of Electronics, Peking University, Beijing 100871, China
2 School of Physics and CRANN, Trinity College, Dublin 2, Ireland
1. Atomic and electronic structures of the infinite one-dimensional polyacene
Figure S1 Atomic structure (a), band structure (b) and DOS (c) of the infinite one-dimensional polyacene
2. Atomic and electronic structures of N-doped graphene
Figure S2 Unit cell (a) and DOS (b) of N-doped graphene with the dopant concentration chosen at 1/28
3. Atomic structure and the electronic transport properties of the C6 alkyne chain connected
directly to two semi-infinite N-doped graphene electrodes
(a)
(b)
Figure S3 Atomic structure (a) and the equilibrium transmission spectrum (b) of the C6 alkyne chain
connected directly to two semi-infinite N-doped graphene electrodes with the dopant concentration
chosen at 1/28
4. The local density of states (LDOS) of the carbon atom at the zigzag edge of the semi-infinite
N-doped graphene electrodes contacted with one C6 alkyne chain through two anthracene groups
(a)
(b)
Figure S4 (a) the atomic structure of a junction comprising one C6 alkyne chain connected to two
N-doped graphene electrodes through two anthracene anchoring groups, the blue dots represent
nitrogen dopants; (b) the LDOS of the carbon atom (labelled with a red X) at the zigzag edge of
the semi-infinite N-doped graphene electrode
5. The spin-polarized electronic transport properties of the junction comprising one C6 alkyne
chain connected to two N-doped graphene electrodes through two anthracene anchoring groups
When ferromagnetic coupling between the two zigzag edges is assumed, the overall shape
of the total transmission spectrum of the junction is almost identical to that of the junction
calculated without spin-polarization but shifts about 60 meV to lower energies. Spin polarization
at the zigzag edges changes a little the alignment of energy levels of the pentacene-C6-pentacene
molecule relative to the Fermi level of the N-doped graphene electrodes, which is illustrate by
the LDOS of the entire molecule in the junction. Around the Fermi level, spin polarization lifts
the degeneracy of the edge state at the zigzag edge: the LDOS peak of the majority electrons
shifts downward to -0.34 eV whereas the LDOS peak of the minority electrons shifts upward to
the Fermi level. As a result, the transmission peak dominated by the edge state is also shifted to
the Fermi level.
(a)
(b)
(c)
Figure S5 (a) the total transmission spectrum of the junction calculated with spin-polarization in
which ferromagnetic coupling between the two zigzag edges is assumed, the transmission
spectrum calculated without spin-polarization is also given for comparison; (b) the spin-resolved
LDOS of one carbon atom at the zigzag edge; (c) the LDOS of the entire molecule including the
C6 alkyne chain and two anthracene molecules calculated with and without spin-polarization.