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# CONDUCTANCE AND TRANSPARENCE OF LONG MOLECULAR WIRES

M. Magoga, C. Joachim
Published 1997 · Physics

Electron tunneling through a molecular wire is studied as a function of the length and chemical structure of the molecule. The current intensity is calculated using the electron-scattering quantum-chemistry technique, the wire being connected at both ends to a planar metal-vacuum-metal nanojunction. The tunnel channels and the stepped $I(V)$ characteristics are discussed in detail for the oligo (thiophene ethynylene) molecular wire. At low bias voltage, the conductance $G$ of a metal-molecular wire-metal junction follows a ${G=G}_{0}{e}^{\ensuremath{-}\ensuremath{\gamma}L}$ law with $L$ the interelectrode separation. The inverse damping length $\ensuremath{\gamma}$ depends on the internal wire electronic structure and the contact conductance ${G}_{0}$ on the electrode-wire end interactions. Both $\ensuremath{\gamma}$ and ${G}_{0}$ can be optimized by changing the chemical structure of the wire, and are given for a large number of oligomers.

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