Interplay of Mechanical and Electrical Degrees of Freedom in Molecular Junctions
F. Pump, C. Toher, and G. Cuniberti
Max Bergmann Symposium 2008
2008.11.04-06; Max Bergmann Center, Dresden, Germany
One of the major obstacles to the use of theoretical and computational methods to understand molecular electronics experiments is the fact that the contact geometry between the molecule and the electrodes is usually not very well known. However, the electronic transport properties of molecular wire junctions are very sensitive to the contact configuration, which makes the synchronization of theory and experiment difficult. One type of molecular electronics experiment which allows more control over the contact geometry is that in which an STM (scanning tunnelling microscope) tip forms one of the electrodes. The imaging capability of the STM enables the investigation of both the electronic and geometric structure of the junction [1-3]. In this poster, we present the results of recent calculations related to a set of STM experiments studying PTCDA on metallic surfaces, using the non-equilibrium Green function formalism in combination with DFT [4-7]. A further aspect of this work which we will present here deals with long-term measurements of the conductance through molecular wire junctions which show a characteristic switching behavior caused by geometrical fluctuations. Both of these approaches allow for the systematic investigation of the effect of the contact geometry on the transport properties of molecular junctions, which should in turn improve the agreement between theory and experiment.
 F. Pump, R. Temirov, O. Neucheva, S. Soubatch, S. Tautz, M. Rohlfing, and G. Cuniberti, Appl. Phys. A 93, 335 (2008).
 M. Rohlfing, R. Temirov, and F. S. Tautz, Phys. Rev. B 76, 115421 (2007).
 R. Temirov, A. Lassise, F. B. Anders, and F. S. Tautz, Nanotechnology 19, 065401 (2008).
 J. M. Soler, E. Artacho, J. D. Gale, A. Garca, J. Junquera, P. Ordejn, and D. Sanchez-Portal, J. Phys. Cond. Matter 14, 2745 (2002).
 A. R. Rocha, V. M. Garcia-Suarez, S. Bailey, C. Lambert, J. Ferrer, and S. Sanvito, Phys. Rev. B 73, 085414 (2006).
 D. Porezag, Th. Frauenheim, Th. Köhler, G. Seifert, and R. Kaschner, Phys. Rev. B 51, 12947 (1995).
 A. Pecchia and A. Di Carlo, Rep. Prog. Phys. 67, 1497 (2004).