Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 67: Gerhard Ertl Young Investigator Award (talks of the selected canditates)
O 67.2: Talk
Thursday, March 25, 2010, 11:00–11:30, H37
Charge Measurement of Atoms and Atomic Resolution of Molecules with Noncontact AFM — •Leo Gross1, Fabian Mohn1, Nikolaj Moll1, Peter Liljeroth1, Jascha Repp2, Franz J. Giessibl2, and Gerhard Meyer1 — 1IBM Research - Zurich, 8803 Rüschlikon, Switzerland — 2Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
Individual gold and silver adatoms and pentacene molecules on ultrathin NaCl films on Cu(111) were investigated using an atomic force microscope (AFM), equipped with a qPlus sensor, operated at 5K.
Charging a gold atom by one electron charge increased the force on the AFM tip by a few piconewtons. Employing Kelvin probe force microscopy (KPFM) we also measured the local contact potential difference (LCPD) which is shifted depending on the sign of the charge. This effect allows the discrimination of positively charged, neutral, and negatively charged atoms.
To image pentacene molecules we modified AFM tips by means of vertical manipulation techniques, i.e. deliberately picking up known atoms and molecules. Using a CO terminated tip we resolved all individual atoms and bonds within a pentacene molecule. By comparison with density functional theory (DFT) calculations we found that atomic resolution is obtained due to the contributions from the Pauli repulsion.