Length-dependent conductance of molecular wires and contact resistance in metal-molecule-metal junctions.
Molecular wires are covalently bonded to gold electrodes--to form metal-molecule-metal junctions--by functionalizing each end with a -SH group. The conductance of a wide variety of molecular junctions is studied theoretically by using first-principles density functional theory (DFT) combined with the nonequilibrium Green's function (NEGF) formalism. Based on the chain-length-dependent conductance of the series of molecular wires, the attenuation factor beta is obtained and compared with the experimental data. The beta value is quantitatively correlated to the molecular HOMO-LUMO gap. Coupling between the metallic electrode and the molecular bridge plays an important role in electron transport. A contact resistance of 6.0+/-2.0 Kohms is obtained by extrapolating the molecular-bridge length to zero. This value is of the same magnitude as the quantum resistance.
Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210008, PR China.
Hongmei
H
Liu
Nan
N
Wang
Jianwei
J
Zhao
Yan
Y
Guo
Xing
X
Yin
Freddy Y C
FY
Boey
Hua
H
Zhang
D004553:Electric Conductivity; D004566:Electrodes; D008670:Metals; D036103:Nanotechnology; D053770:Nanowires / Q000737:chemistry*; D009930:Organic Chemicals
D008670:Metals; D009930:Organic Chemicals