Regensburg 2007 – wissenschaftliches Programm

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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices

SYOE 8: Poster Session SYOE

SYOE 8.2: Poster

Dienstag, 27. März 2007, 18:00–20:00, Poster B

Chemical Bonding and Charge Distribution at Metallic and Molecular Nanocontacts — •Cosima Schuster and Udo Schwingenschlögl — Institut für Physik, Universität Augsburg, 86135 Augsburg

Electrical properties of metallic nanocontacts or molecular devices are addressed by the transport through a central atom or a molecule sandwiched between metallic electrodes. The resulting transport characteristics reflects both the metal-molecule contact and the molecule itself. The features of a nanocontact device strongly depend on the local electronic structure at the different molecular sites. Details of the chemical bonding, such as hybridization or charge transfer hence play a key role for understanding the device, and structural relaxation due to the metal-molecule contact has to be taken into consideration. We investigate the local electronic structure for various aluminium nanocontact geometries and the gold-dithiolbenzene transport interface. Our investigations result in two characteristic features: the suppression of hybridization and the violation of charge neutrality at the neck of the contact. Since both features trace back to the spacial restriction of the crystal structure due to the contact, they are typical of metallic nanocontacts in general. The influence of the particular shape of the nanocontact and the experimental setup is discussed. Especially, for the gold-dithiolbenzene transport interface we find that the local DOS at carbon sites without sulfur bonding almost vanishes at the Fermi energy, which explains the experimental observation of an insulating state.