Large organic molecules have recently attracted interest from a fundamental point of view and for prospective applications in nanoelectronics [1,2]. In particular, several studies have indicated that upon molecular adsorption surfaces often do not behave as static checkerboards, but may rearrange to accommodate the different molecular species. We investigate the adsorption of C90H98 (Lander molecule) on the Cu(110) surface in the temperature range 100 - 300 K by STM. The Lander molecule has a central polyaromatic molecular "wire" terminated by a fluoranthene group (conducting backbone), and four "spacer legs" (3,5-di-tert-butylphenyl substituents - Tbp); the function of these legs is to isolate the conducting backbone from the substrate.
The molecule is imaged by STM as four bright lobes. From an interplay with Elastic Scattering Quantum Chemistry theoretical calculations, we deduce that the lobes correspond to tunneling through the legs of the molecule.
Very surprisingly, when the isolated Lander molecules adsorbed on step edges is manipulated away from the step a tooth-like structure appears, as shown in Fig. 1. The structure's width is two atomic rows, corresponding to the distance between the spacer legs within the molecule . Repeating the same manipulation experiments on molecules adsorbed at low temperatures (150 K), no restructuring of the Cu step edges is found. The process is thus thermally activated.
This is the first prototype of more complex molecular machines able to self-fabricate nanostructures with the prospect of developing planar and atomically precise interconnections of molecular nanodevices.
T.A. Jung, R.R. Schlitter, J.K. Gimzewski, H. tang and C. Joachim, Sience271, 181 (1996)
C. Joachim, J.K. Gimzewski and A. Aviram, "Electronics using hybrid-molecular and mono-molecular devices", Nature408, 541 (2000).
F. Rosei, M. Schunack, P. Jiang, A. Gourdon, E. Laegsgaard, I. Stensgaard, C. Joachim and F. Besenbacher, "Organic Molecules acting as Templates on Metal Surfaces", Science296, 328 (2002).