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O: Fachverband Oberflächenphysik
O 101: Scanning Probe Techniques: AFM
O 101.7: Vortrag
Freitag, 20. März 2015, 12:00–12:15, MA 144
The Meaning of Temperature in Interferometric Detection Schemes — •Alexander Schwarz1, Gotthold Fläschner1, Kai Ruschmeier1, Roland Wiesendanger1, Reza Bakhtiari2, and Michael Thorwart2 — 1University of Hamburg, Institute of Applied Physics, Jungiusstr.11, 20355 Hamburg — 2University of Hamburg, I. Institute of Theoretical Physics, Jungiusstr. 9, 20355 Hamburg
The force sensitivity of cantilevers used in atomic force microscopy (AFM) scales with √T. A convenient way to obtain the temperature T is measuring the power spectral density around the resonance frequency and subsequent application of the equipartition theorem. However, in interferometric detection schemes, where the backside of the cantilever acts as one mirror of a Fabry-Perot cavity, the dynamic of the cantilever motion can be influenced by the light, e.g., due to photothermal effects [1,2]. In this case the so-called mode temperature and not the phonon temperature is measured.
In our presentation we describe a procedure to determine the phonon temperature of the cantilever for a Fabry-Perot type interferometric detection scheme, if radiation pressure dominates over photothermal effects. Moreover, we also explain how laser noise can influence the cantilever motion. Our analysis shows that the recorded power spectral density are best described by Fano line shapes, which can exhibit a dip instead of a peak at resonance. Indeed, we were able to observe such a peculiar antiresonant behavior experimentally.
[1] C. H. Metzger and K. Karrai, Nature 432, 1002 (2004).
[2] H. Hölscher et al., Appl. Phys. Lett. 94, 223514 (2009).