Berlin 2012 – wissenschaftliches Programm

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MI: Fachverband Mikrosonden

MI 8: Poster – Microanalysis and microscopy

MI 8.12: Poster

Mittwoch, 28. März 2012, 15:00–17:30, Poster E

How to operate a non-contact atomic force microscope (NC-AFM) for ultra-high vacuum applications at the thermal noise limit — •Matthias Temmen¹, Jannis Lübbe¹, Sebastian Rode², Philipp Rahe², Angelika Kühnle², and Michael Reichling¹ — ¹Fachbereich Physik, Universität Osnabrück, Germany — ²Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, Germany

The total noise in the frequency shift signal Δ f of NC-AFM measurements consists of thermal noise, tip-surface interaction noise and instrumental noise from the detection and signal processing systems. We investigate the deflection noise spectral density (d^z) at the input of the frequence demodulator (PLL) as well as the frequency noise spectral density (d^{Δ f}) at the output depending on cantilever properties and settings of the signal processing electronics for the case of negligible tip-surface interaction. For a quantification of noise figures we calibrate the cantilever deflection signal and determine the signal processing electronics transfer function to we derive predictions for the frequency noise spectral density for various filter settings and different levels of detection system noise (d_ds^z). We demonstrate that an optimised system with low noise signal detection operated with appropriate settings allows room temperature operation at the thermal noise limit of the NC-AFM with a significant bandwidth.