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.
Liu
Hongmei
H
Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210008, PR China.
Wang
Nan
N
Zhao
Jianwei
J
Guo
Yan
Y
Yin
Xing
X
Boey
Freddy Y C
FY
Zhang
Hua
H
D004553:Electric Conductivity; D004566:Electrodes; D008670:Metals; D036103:Nanotechnology; D053770:Nanowires / Q000737:chemistry*; D009930:Organic Chemicals
D008670:Metals; D009930:Organic Chemicals