•H. v. Löhneysen^1,2, F. Hennrich³, M.M. Kappes³, R. Krupke³, M. Mayor³, J. Reichert³ und H.B. Weber^3
3Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76344 Karlsruhe
¹Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe
²Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76344 Karlsruhe

Electronic transport measurements through single p-conjugated molecules can be realized using mechanically controlled break junctions to couple thiol end groups of the molecules to two gold electrodes. We have investigated transport through p-conjugated molecules which differ by their spatial symmetry and p-conjugated connectivity. The current voltage characteristics (IVs) of the metal-molecule-metal system reflect the spatial symmetry and topology of the molecules with respect to the direction of current flow indicating that transport occurs indeed through single molecules [1]. Fluctuations in the IVs are a manifestation of the variation of level spacings of the system, which depend crucially on the bonding between thiol end groups and Au electrodes.

For the future electronics, carbon nanotubes are the prime candidates. Recent progress in the controlled deposition of nanotubes between electrodes and separation of metallic and semiconducting nanotubes [2] is reported.

[1] J. Reichert et al., Phys. Rev. Lett. 88, 176804 (2002)

[2] R. Krupke et al., Science 301, 344 (2003)