Berlin 2012 – wissenschaftliches Programm
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MI: Fachverband Mikrosonden
MI 3: Scanning probe microscopy
MI 3.4: Vortrag
Montag, 26. März 2012, 13:30–13:45, EMH 225
Extracting intrinsic cantilever properties from thermal noise — •Jannis Lübbe1, Matthias Temmen1, Philipp Rahe2, Angelika Kühnle2, and Michael Reichling1 — 1Fachbereich Physik, Universität Osnabrück, Barbarastraße 7, 49076 Osnabrück, Germany — 2Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, Jakob-Welder-Weg 11, 55099 Mainz, Germany
We describe a method to determine the eigenfrequency f0, the intrinsic quality factor Q0 and the stiffness k from the cantilever deflection noise spectral density dthz(f) of a thermally excited cantilever in an ultra-high vacuum environment. The precision of the f0 value as derived from the peak position is of the order of 0.1 % and solely limited by thermal drift. The Q0 value can be determined from a fit with a precision of 10 %. Most delicate is the determination of k derived from the fit of the dthz(f) curve. This measurement requires a calibration of the deflection measurement and utmost care has to be taken to avoid any excitation of the cantilever other than by thermal noise. An alternative approach is to determine dynamic stiffness from a measurement of the spectral density dthΔ f(f) of the frequency demodulated thermal noise signal. This approach can easily be extended to a measurement of higher order eigenmodes as the spectral analysis of dthΔ f(f) can mostly be restricted to frequencies below 100 Hz and does not require high spectral resolution. Results obtained from the two methods are in good agreement with each other.