| AVS 54th International Symposium | |
| Surface Science | Monday Sessions |
| Session SS2-MoA |
| Session: | Electronic and Vibrational Structure |
| Presenter: | L. Bartels, University of California, Riverside |
| Authors: | K.L. Wong, University of California, Riverside G. Pawin, University of California, Riverside D.H. Kim, University of California, Riverside L. Bartels, University of California, Riverside |
| Correspondent: | Click to Email |
Thiol groups, despite being proposed as rigid linker for many molecular electronics applications, anchor aromatic molecules to metal surfaces in a fashion that permits rapid rearrangement of the molecule on the substrate even at temperatures as low as 60K. The aromatic ring of individual benzenethiol molecules experiences a rotation barrier around the substrate linker of ca. 120 meV; even diffusion of the sulfur anchor on the substrate has a barrier of only ca. 150 meV.1 Placement of two thiol groups in a molecule (9,10-dithionanthracene, DTA) does not increase the diffusion barrier. Rather it renders the moleculeâ?Ts diffusion behaviour on Cu(111) anisotropic, i.e. following a single line on the otherwise threefold symmetric substrate.2 Density functional theory calculations show, that this behaviour originates from sequential occupation of optimal adsites by each of the two substrate linkers, strikingly resembling bipedal locomotion ("walking"). The resultant linear (uniaxial) motion on the surface can be used for transport of "cargo" molecules across a surface3 as well as for the exploration of fundamental concepts of chemistry.
1 K.L. Wong et al., Appl. Phys. Lett. 88, 183106 (2006)
2 K.-Y. Kwon et al., Phys. Rev. Lett. 95, 166101 (2005)
3 K.L. Wong et al., Science 315, 1391 (2007)