Synopsis: Tuning conductance

A single-molecule junction on a silver surface exhibits orders-of-magnitude variation in conductance.

Electron transport through molecules has implications for a range of subjects. In particular, conductance through single-molecule junctions is known to have a complex dependence on atomic structure, orientation, and bonding properties. However, investigations with atomic-scale control of the junction geometry are scarce.

In their paper in Physical Review Letters, Yongfeng Wang and collaborators from Germany, Denmark, and Sweden demonstrate that the conductance in a single-molecule junction varies over orders of magnitude.

Wang et al. present scanning tunneling microscopy measurements of the conductance of tin-phthalocyanine ($\text{SnPc}$) adsorbed on a $\text{Ag}\left(111\right)$ surface in contact with a tungsten tip covered with silver. By manipulating the chemical bonding between $\text{SnPc}$ and $\text{Ag}\left(111\right)$ through selective dehydrogenation of $\text{SnPc}$ and an atomic-scale structuring of the electrode, the conductance of single-molecule junctions is varied from $0.013$ to $0.32$ in units of the quantum of conductance. The authors also perform ab initio calculations combined with a nonequilibrium Green’s function technique for a quantitative analysis of the electron transport through $\text{Ag-SnPc-Ag}$ junctions. This opens an avenue to study current flow through single molecules by combining transport measurements with atomic manipulation capabilities of the scanning tunneling microscope. – Sarma Kancharla

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