Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 43: Poster Session II - MA 141/144 (Surface Spectroscopy on Kondo Systems; Frontiers of Surface Sensitive Electron Microscopy; Methods: Scanning Probe Techniques+Electronic Structure Theory+Other; Time-Resolved Spectroscopy of Surface Dynamics with EUV and XUV Radiation; joined by SYNF posters)
O 43.31: Poster
Tuesday, February 26, 2008, 18:30–19:30, Poster F
Towards a quantitative determination of charge distribution and local potential by Phase-Electrostatic Force Microscopy: theory and applications — •Cristiano Albonetti, Paolo Annibale, and Fabio Biscarini — CNR-Institute for the Study of Nanostructured Materials (ISMN), Bologna, Italy
The cantilever phase signal of the atomic force microscope, in conjunction to lift-mode operation, is used to map the electrostatic interaction between the cantilever’s tip and the sample with a lateral resolution less than 50 nm. The detection of the phase, sensitive to tip-sample force gradient, allows to gain a higher resolution with respect to more conventional electrostatic probes based on force detection. Relevant organic and inorganic samples, with well-defined morphology, were measured by modeling the tip-sample electrostatic interaction in the prolate spherical coordinates reference system. Layered α-sexithiophene ultra-thin films grown on Si/SiOx substrate show a monotonic decrease of the local surface potentials with the increase of the surface coverage, consistently with the predicted confinement at the first few monolayers of the charge accumulation layer (organic sample). Silicon oxide nano-stripes, made by scanning probe lithography, show a variable electrostatic contrast due to a different amount of charges trapped in the oxide, thus yielding significant information about the mechanism of the oxidation process (inorganic sample). The application of this technique to operating thin film organic field effect transistors allows to correlate local surface potential with the morphology of the transistor channel.