Abstract_Ernst Meyer

Ernst Meyer

University of Basel, Dep. of Physics

Graphene Nanoribbons and Polymeric Chains Sliding on Au(111)

Manipulative force microscopy uses the probing tip to pick up a single molecule or nanoribbons and to perform a number of experiments with the attached molecule. Either lateral or vertical manipulations can be performed, where a number of parameters, such as velocity, temperature or orientation angle, are available. An example is given by the pulling of polymeric chains on Au(111) [1], where the detachment of the chain leads to oscillations of the normal and lateral forces. The comparison with the model yields the adhesive energy per subunit of the molecular chain. Lateral manipulation gives insight into the movement of one dimensional chains on surfaces. An example with potential for application is the pulling of graphene nanoribbons across an Au surface [2]. In this case, superlubricity conditions were found. The movement in the [-101] direction shows a rather high degree of incommensurability. The graphene ribbon shows quite high stiffness, which even allows us to reverse the sliding direction with small hysteresis. A second class of experiments is to pick up a single molecule and to investigate the influence of internal degrees of freedom during lateral and vertical manipulations [3]. In the case of a porphyrin derivative it is the motion of a di-cyanophenyl side group, which determines the mechanical response. This method is also useful to observe inhomogeneities on the surface, e.g. the elbow sites of the herringbone reconstruction.
[1] S. Kawai, M. Koch, E. Gnecco, A. Sadeghi, R. Pawlak, Th. Glatzel, J. Schwarz, S. Goedecker, S. Hecht, A. Baratoff, L. Grill, and E. Meyer, Proc.
Natl. Acad. Sci. USA, 111, (11), 3968?3972 (2014).
[2] S. Kawai, A. Benassi, E. Gnecco, H. Söde, R. Pawlak, X. Feng, K. Müllen, D. Passerone, C. A. Pignedoli, P. Ruffieux, R. Fasel, E. Meyer
Science, 351, (6276), 957 (2016).
[3] R. Pawlak, W. Ouyang, A. E. Filippov, L. Kalikhman-Razvozov, S. Kawai, T. Glatzel, E. Gnecco, A. Baratoff , Q.-S. Zheng, O. Hod, M. Urbakh,
E. Meyer, ACS Nano, 10, 713-722 (2016).