title: Force field analysis suggests a lowering of diffusion barriers in atomic manipulation due to presence of STM tip.
abstract: We study the physics of atomic manipulation of CO on a Cu(111) surface by combined scanning tunneling microscopy and atomic force microscopy at liquid helium temperatures. In atomic manipulation, an adsorbed atom or molecule is arranged on the surface using the interaction of the adsorbate with substrate and tip. While previous experiments are consistent with a linear superposition model of tip and substrate forces, we find that the force threshold depends on the force field of the tip. Here, we use carbon monoxide front atom identification (COFI) to characterize the tip's force field. Tips that show COFI profiles with an attractive center can manipulate CO in any direction while tips with a repulsive center can only manipulate in certain directions. The force thresholds are independent of bias voltage in a range from 1 to 10 mV and independent of temperature in a range of 4.5 to 7.5 K.
authors.affiliation: Institute of Experimental and Applied Physics, University of Regensburg, D-93053 Regensburg, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Emmrich
authors.affiliation: Institute of Experimental and Applied Physics, University of Regensburg, D-93053 Regensburg, Germany.
authors.forename: Maximilian
authors.initials: M
authors.lastname: Schneiderbauer
authors.affiliation: Institute of Experimental and Applied Physics, University of Regensburg, D-93053 Regensburg, Germany.
authors.forename: Ferdinand
authors.initials: F
authors.lastname: Huber
authors.affiliation: Institute of Experimental and Applied Physics, University of Regensburg, D-93053 Regensburg, Germany.
authors.forename: Alfred J
authors.initials: AJ
authors.lastname: Weymouth
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Okabayashi
authors.affiliation: Institute of Experimental and Applied Physics, University of Regensburg, D-93053 Regensburg, Germany.
authors.forename: Franz J
authors.initials: FJ
authors.lastname: Giessibl