Monday 15 September 2014
to 11:00 at
Astrid S. de Wijn (Molecular Physics Department)
A unique path to control and ultimately manipulate forces between material surfaces is through an applied electric field. Several experimental and theoretical studies of electro chemical interfaces demonstrated that the
orientation of polar molecules adsorbed at electrode surfaces is potential dependent. We propose a theoretical model for friction under electrochemical conditions focusing on the interaction of a force microscope tip with adsorbed
polar molecules of which the orientation depends on the applied electric field. The dependence of friction force on the electric field is shown to be determined by the interplay of two channels of energy dissipation: (i) the rotation of dipoles and (ii) slips of the tip over potential barriers.
Strategies for achieving a strong dependence of nanoscopic friction on the external field is identified based on the competition between long range electrostatic interactions and short range chemical interactions between tip and adsorbed polar molecules. The effects of molecule geometry and oscillating fields are investigated as well.
 Nanoscopic friction under electrochemical control
A. S. de Wijn, A. Fasolino, A. Filippov, M. Urbakh Phys. Rev. Lett. 112, 055502 (2014).