Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 15: Scanning Probe Techniques: STM/AFM

O 15.7: Vortrag

Montag, 16. März 2015, 16:30–16:45, MA 043

Force Field Analysis of STM/AFM Tips for Atomic Manipulation — Matthias Emmrich, Maximilian Schneiderbauer, •Ferdinand Huber, Alfred John Weymouth, and Franz Josef Giessibl — Institute for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany

Atomic manipulation of single atoms and molecules by scanning tunneling microscopy (STM) relies on the force field the tip exerts on the adsorbate that is to be moved. We use combined STM and atomic force microscopy (AFM) operating at low temperature to analyze the force field between metallic tips and a CO molecule adsorbed on a Cu(111) surface [1]. We relate the force field of the tip to its suitability for reliable atomic manipulation and we find that the STM channel alone can lead to incorrect identifications of the pushing, pulling and sliding modes that have previously been identified. Circularly symmetric tips, obtained by poking, yield the most reliable manipulation. The symmetry of the force field can be assessed indirectly by evaluation of the manipulation pattern in the STM channel. In the first publication on manipulation forces [2], a lateral force of 160 ± 30 pN has been measured to move CO across Cu(111) at a temperature of 5 K. Here, we find that 96 pN suffices at a temperature of 7.5 K, suggesting that thermal excitation assists atomic manipulation.

[1] M. Emmrich, M. Schneiderbauer, F. Huber, A. J. Weymouth and F. J. Giessibl, submitted (2014)

[2] M. Ternes, C. P. Lutz, C. F. Hirjibehedin, F. J. Giessibl and A. J. Heinrich, Science 319, 1066 (2008)