Supporting information for: Electron Transport Properties of Atomic Carbon Nanowires between Graphene Electrodes Lei Shen,,, Minggang Zeng,,, Shuo-Wang Yang,, Chun Zhang, Xuefeng Wang, and Yuanping Feng, Department of Physics, 2 Science drive 3, National University of Singapore, Singapore 117542, Singapore, Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Singapore, NanoCore, 5A Engineering Drive 4, National University of Singapore, Singapore 117576, Singapore, and Department of Physics, Soochow University, Suzhou 215006, China E-mail: yangsw@ihpc.a-star.edu.sg; phyfyp@nus.edu.sg To whom correspondence should be addressed National University of Singapore (NUS Institute of High Performance Computing (IHPC National University of Singapore (NUS Soochow University These authors contributed equally to this work S1
(a SP Carbon chain lead (b Carbon chain lead Carbon ribbon lead (c SP 2 Carbon ribbon lead Carbon tube lead (d SP 3 Carbon tube lead Metal bulk lead SP 3 Metal bulk lead Figure S 1: (Color online Schematic diagrams of different configurations of carbon wires and electrodes. A linear atomic carbon wire has (a sp connection with carbon wire leads; (b sp 2 connection with carbon ribbon leads (optimized; (c sp 3 connection with capped carbon tube leads; (d sp 3 connection with metal leads. S2
(a (b (c zigzag Figure S 2: (Color online Three optimized structural configurations of carbon wire-graphene junctions. (a five-membered carbon ring (b six-membered carbon ring (c three-membered carbon ring. The six-membered ring connection structure is the most energetical favor than the other two. Three different connection-points are labeled as (1,6, (2,5 and (3,4. (orange: H; grey: C S3
1.4 1.2 (a Zigzag connecting edge 1.4 1.2 (b reconstructed zigzag (57 1.0 1.0 T (G 0 0.8 0.6 T (G 0 0.8 0.6 0.4 0.4 0.2 0.2-2 -1 0 1 2 E- -2-1 0 1 2 E- Figure S 3: (Color online (a The transmission spectrum of C 7 with the zigzag connecting edge. (b The transmission spectrum of C 7 with the reconstructed (57 zigzag edge. As can be seen, the connecting edge (zigzag or armchair does not obviously affect the transport property near the Fermi level. But the edge reconstruction does a strong suppression of transmission ( 50% due to the disruption of edge states. S4
1.0 0.8 C 7 carbon chain between armchair-edge graphene nanoribbon electrodes T (G 0 0.6 0.4 0.2-4 -2 0 2 4 E- Figure S 4: (Color online The transmission of a C 7 carbon chain between armchair-edge graphene nanoribbon electrodes (i = 7. There is a poor conductance near the Fermi level due the semiconducting property of armchair-edge GNR electrodes. S5
1.5 4 surface layers 8 surface layers 16 surface layers Transmission (G 0 1.0 0.5-2.0-1.5-1.0-0.5 0.5 1.0 1.5 2.0 E- Figure S 5: (Color online Different width surface layers of seven carbon chains are tested in order to investigate the effect of distance between the two electrodes. This is because enough surface layers are essential in order to properly screen the induced electric field between two close electrodes. As can be seen, the transport property of the carbon chains does not change appreciably when the surface layers are four or more. S6
(a C 7 126.85 O 1.26 1.28 1.30 123.24 1.30 1.28 120 O 1.26 113.13 O O (b C 8 127.33 O 1.23 1.24 1.24 1.24 123.70 O 1.33 1.33 1.33 120.53 O 112.15 O (c C 15 127.12 O 1.31 1.30 1.29 1.28 1.27 1.26 123.61 O 1.25 1.25 1.26 1.27 1.28 1.29 1.30 1.31 120.35 O 112.66 O (d C 16 127.19 O 1.33 1.32 1.32 1.32 1.32 1.32 1.33 123.62 O 1.24 1.25 1.25 1.25 1.25 1.25 1.25 120.46 O 1.24 112.47 O Figure S 6: (Color online (a-(d The optimized scattering region of C 7, C 8, C 15, and C 16 structures. the wires consisting of odd number of carbon atoms favor cumulene ( C=C=C=C ((a and (c, but those consisting of even number of carbon atoms prefer polyyne ( C C C C ((b and (d. S7
(a (b N=7 (odd (c N=8 (even (d oxygen (e hydrogen (f double chains ring Figure S 7: (Color online (a-(f Electron density of carbon wire-graphene junctions. The different bonding configurations of odd-numbered carbon wires (a and even-numbered carbon wires (b can be seen from their electron density distribution. The adsorbed oxygen atom (c, apt to epoxy, which can block the electrical current due to the electron trap property of oxygen atoms. The calculated conductance of double wires is less than twice of a singe wire. This is due to the spatial overlapping of electron cloud between two wires as shown in (e. S8
(a (b (c (N-1/2 Molecular orbitals of a free odd-number carbon chain (d N/2 Molecular orbitals of a free even-number carbon chain e electrode (electron reservior (e XX (N-1/2 Coupled with electrodes and charge-transfer e N/2 electrode not occupied partially occupied half occupied fully occupied electrode (N-1/2+1 alignment of and a partially occupied (f electrode electrode electrode electrode electrode (electron reservior N/2+1 Figure S 8: (Color online (a Molecular orbitals of a free odd-numbered carbon wire (molecule with (N 1/2 fully occupied. (b A free carbon wire is coupled with electrodes and charge-transfer occurs which make empty of the free carbon wire becoming partially occupied. (c Alignment of the Fermi level of electrodes and a partially occupied, resulting in electron transport from left electrode to right electrode. (dmolecular orbitals of a free evennumbered carbon wire with N/2 fully occupied and one half-occupied. (e A free carbon wire is coupled with electrodes and charge-transfer occurs which make the half-occupied becoming partially occupied. (f Alignment of the Fermi level of electrodes and a partially occupied. Therefore, both odd- and even-numbered carbon wire are conductible when they are coupled with electrodes. S9
(a C 7 (b C 8 Density of States Density of States -0.5 0.5-0.5 0.5 E- E- Figure S 9: (Color online (adensity of states of C 7 at the Fermi level; (bdensity of states of C 8 at the Fermi level. Higher density of states at the Fermi level, higher transmission at the Fermi level. S10
(a 1.0 C 8 -H 1.0 (b C 8 -O Transmission (G 0 0.8 0.6 0.4 0.2 Transmission (G 0 0.8 0.6 0.4 0.2-0.2-0.1 0.1 0.2-0.2-0.1 0.1 0.2 E- E- Figure S 10: (Color online (a The enlarged view of the transmission spectrum of hydrogen adsorbed C 8 near the Fermi level. (b The enlarged view of the transmission spectrum of oxygen adsorbed C 8 near the Fermi level. S11