Regensburg 2013 – scientific programme

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MI: Fachverband Mikrosonden

MI 9: Poster: Microanalysis and Microscopy

MI 9.6: Poster

Wednesday, March 13, 2013, 15:00–17:00, Poster B2

Characterization of Mechanical Properties of qPlus Sensors — •Jan Berger, Martin Švec, Martin Müller, Martin Ledinský, Antonín Fejfar, Pavel Jelínek, and Zsolt Majzik — 1Institute of Physics of the Czech Academy of Science, Prague, 162 00, Czech republic

Tuning fork based sensors (qPlus) became frequently used in non-contact atomic force microscopy (nc-AFM) last years. However, precise characterization of mechanical properties of each sensor is crucial for proper estimation of measured quantities such as forces or the dissipation energy. If a prong of the tuning fork is shortened to achieve higher electrical sensitivities (i.e. to produce more charge per oscillation) the mechanical parameters must be calibrated again.

In this poster we present a comparison of three different methods that can be used for estimating the stiffness of qPlus sensors. The first method is based on continuum theory of elasticity. The second (Cleveland's method) uses change in the eigenfrequency, which is induced by loading of small masses. Finally, the stiffness is obtained by analyses of the thermal noise spectrum. We show that all three methods give similar results. Surprisingly, neither the gold wire nor the gluing rise to significant changes of the stiffness.

We describe a fast and cost-effective way to perform the Cleveland's method, based on gluing small pieces of a tungsten wire. The mass is obtained from the volume of the wire, which is measured by optical microscope. For detection of oscillation eigenfrequencies under ambient conditions, we designed and built a device for testing qPlus sensors.