MS&E Colloquium
Date: May 02, 2008 from 2:00 pm to 3:00 pm EDT
Location: 214 S. W. Mudd
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Construction and Physical Properties of a Single Molecular Device*


Hongjun Gao

Beijing National Laboratory of Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, PO Box 603, Beijing 100190, China


Constructing single molecular devices of functionalities has stimulated a great interest in the past decades. One of the challenges in this field is to make the single molecule stably connected to a single metal atom on metal surfaces, and further to make the molecule create electric energy and optical/electro radiation by rotating the molecule. Here we report that by using Au adatoms of the Au(111) surface we have successfully formed a single molecule rotor array, isolated tetra-tert-butyl Zinc Phthalocyanine ((t-Bu)4-ZnPc) molecules sticking to the Au adatoms of the Au(111) and rotating on the surface at 78 K.  This kind of single molecular rotor was also found to be controlled by the different sites of the Au(111) surface using low temperature scanning tunneling microscopy (STM).  On the other hand, changing the molecular structure by using the same molecular family of the Pc, ZnPc and FePc, can also modulate the rotation behavior of the molecules.   The finding of controlling over the molecular thermal rotation has established a solid route to connect a single molecular rotor to a single Au atom of Au(111) surface, and may lead to formation of practically single-molecular electric generator and/or radiator devices.  A further study of single FePc molecule on Au(111) substrate show that both the Kondo temperature and the line shape of dI/dV spectra are greatly influenced by molecular adsorption configuration on the Au(111) substrate.  This implies that it is feasible to control the local spin coupling and the competition between different tunneling channels in molecular Kondo effect by changing the molecular adsorption configuration.  Given that the lateral structure of a molecular interface can be modified by the attachment of ligands, the finding opens up the possibility to tailor magnetic properties of an organic interface to the desired specifications.

1 Z. T. Deng et al., Phys. Rev. Lett. 96, 156102 (2006).

2 W. Ji et al., Phys. Rev. Lett. 97, 246101 (2006).

3 D.X. Shi et al., Phys. Rev. Lett. 96, 226101 (2006).

4 L. Gao et al., Surf. Sci. 601, 3179 (2007).

5 M. Feng et al., J. Am. Chem. Soc 129, 2204 (2007).


* In collaboration with D.X. Shia, S.X. Dua, W. Jia, Z.H. Chenga, W.A. Hoferb,

a Institute of Physics, Chinese Academy of Sciences, China; bLiverpool, Britain. The University of