Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 17: Nanotribulogy

O 17.1: Talk

Monday, March 26, 2012, 16:00–16:15, A 053

Imaging and energy dissipation mechanisms on metallic and insulating surfaces studied with AFM in pendulum geometry — •Markus Langer, Marcin Kisiel, Urs Gysin, and Ernst Meyer — Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056, Switzerland

In pendulum geometry the Cantilever is oscillating perpendicular to the sample surface. This opens the possibility to use ultra sensitive cantilever with spring constants of mN/m with a force sensitivity of 10aN/√Hz. For surface characterisation of mixed materials its useful to image the surface topography first. Calculations show that in pendulum geometry the contrast mechanism is influenced by two types of forces - the axial force and the lateral force gradient. This is confirmed experimentally. To study the electronic contribution in detail, it is necessary to compensate the electrostatic force present due to contact potential difference between the cantilever tip and the sample surface. We used frequency modulated - Kelvin Probe Force Microscopy (fm-KPFM) to compensate the contact potential.
We can distinguish between metallic and insulating surfaces an determine the electronic contribution to the energy dissipation. This effect is enhanced, if we gently functionalize the probe, by covering the tip apex with an insulator or metal.
The measurements are performed on Cu(100) substrate with 0.6ML coverage of NaCl. All experiments are done under UHV and cryogenic conditions (77K).