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O: Fachverband Oberflächenphysik

O 99: Scanning Probe Methods III

O 99.9: Vortrag

Freitag, 4. April 2014, 12:30–12:45, GER 38

Current driven forces in molecular junctions — Zsolt Majzik, Prokop Hapala, Ondrej Krejci, Martin Setvin, and •Pavel Jelinek — Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic

We performed simultaneous nc-AFM/STM measurements over acetophenon molecule deposited on Si(100) p-doped surface in an upright position. Simultaneously tunnelling current and frequency shift as function of tip-sample distance and bias voltage allows us to identify presence of new current driven force acting in molecular junction. In far distance regime, we observe well-known parabolic dependence of frequency shift on applied voltage due to long-range electrostatic force. In close distance regime, the new attractive force emerges at positive bias voltage. What more the force changes sign with further tip approach. We will discuss the origin of the force and the sign change with distance.