Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 36: Surfaces and Films: Forces, Structure and Manipulation
O 36.3: Talk
Tuesday, February 26, 2008, 14:45–15:00, MA 041
The Force to Move an Atom — •Markus Ternes1, Christopher P. Lutz1, Cyrus F. Hirjibehedin1, Franz J. Giessibl2, and Andreas J. Heinrich1 — 1IBM Research Division, Almaden Research Center, San Jose, USA — 2Institute of Experimental and Applied Physics, University of Regensburg, Regensburg, Germany
Atomic manipulation of single atoms and molecules by scanning probe microscopy enables the assembly of structures at the single-atom scale -- the ultimate lower size limit. However, it has been difficult to answer the simple question: How much force does it take to manipulate atoms and molecules on surfaces? To address this question, we used a combined atomic force and scanning tunneling microscope to simultaneously measure the force and the current between an adsorbate and a tip during atomic manipulation.
We found that the force it takes to move an atom depends crucially on the binding between adsorbate and surface. Our results indicate that for moving metal atoms on metal surfaces, the lateral force component plays the dominant role. In contrast, we found that the forces to manipulate molecular adsorbates, such as carbon monoxide (CO), were markedly different.
Measuring the forces during manipulation yielded the full potential energy landscape of the tip-sample interaction. Surprisingly, the potential energy barriers are comparable to diffusion barriers, which are obtained in the absence of a probe tip.