Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 68: Focussed session: Functional molecules at surfaces III

O 68.2: Topical Talk

Thursday, March 29, 2012, 11:00–11:30, A 053

Directional motion of a four-wheeled molecule on a metal surface — •Manfred Parschau — Empa - Swiss Federal Laboratories for Materials Science and Technology , Nanoscale Materials Science Laboratory, Ueberlandstrasse 129, CH-8600 Dübendorf, Switzerland

Propelling single molecules in a controlled manner along an unmodified surface remains extremely challenging because it requires molecules that can use light, chemical or electrical energy to modulate their interaction with the surface in a way that generates motion. Although controlled movement of molecules along a surface has been reported, the molecules in these examples act as passive elements that either diffuse along a preferential direction with equal probability for forward and backward movement or are dragged by a tip of a scanning tunneling microscope. Here I present a molecule with four functional units that undergo continuous and defined conformational changes upon sequential electronic and vibrational excitation. Scanning tunneling microscopy confirms that activation of the conformational changes of the rotators through inelastic electron tunneling propels the molecule unidirectionally across a Cu(111) surface. The system can be adapted to follow either linear or random surface trajectories or to remain stationary, by tuning the chirality of the individual motor units.