Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 74: Nanostructures at surfaces: Other

O 74.11: Vortrag

Donnerstag, 25. März 2010, 17:30–17:45, H34

Theoretical investigation of the switching mechanism in a single-molecule memory unit — •Felix Hanke and Mats Persson — University of Liverpool, Liverpool, United Kingdom

The storage and retrieval of information at the sub-nanometer scale is one of the outstanding challenges in nanoelectronics. It was recently proposed that the molecular switch naphthalocyanine can be controlled using scanning-tunneling microscopy (STM) [1] when it is adsorbed on a thin layer of NaCl. The on/off state of naphthalocyanine is determined by the orientation of two central hydrogen atoms, which changes with the application of a high STM voltage, while a low voltage allows to read out the molecular state. Despite the wealth of available experimental information, the electronic processes responsible for the STM-induced configurational changes in naphthalocyanine are poorly understood theoretically. This project aims to explain the switching property based on density functional theory. From the adsorption geometry on the NaCl surface, the reaction path for the switching pathway is computed. This result leads to a detailed investigation of the molecular orbitals responsible for the tunneling-induced motion of the central hydrogen atoms. In particular, the evolution of the lowest two unoccupied and nearly degenerate molecular orbitals is shown to be an important piece in the puzzle. Finally, a model is developed to take into account the electron-induced motion of naphthalocyanine along its switching pathway. - [1] P. Liljeroth et al., Science 317, 1203 (2007)