Dresden 2014 – scientific programme

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MI: Fachverband Mikrosonden

MI 8: Poster: Microanalysis and Microscopy

MI 8.5: Poster

Wednesday, April 2, 2014, 17:00–19:30, P4

Sensitivity in SubSurface-AFM: Tip-Sample Interaction in Heterodyne Force Microscopy — •Gerard J. Verbiest¹, Tjerk H. Oosterkamp², and Marcel J. Rost² — ¹JARA- FIT and II. Institute of Physics, RWTH Aachen University, 52074 Aachen, Germany — ²Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands

A couple of reported Heterodyne Force Microscopy (HFM) measurements demonstrate the unique possibility to nondestructively image 20 nm small nanoparticles buried 500 nm below a surface with an AFM. HFM utilizes two ultrasonic signals of slightly different frequencies that are sent through the sample and the cantilever, respectively. The sound wave through the sample contains subsurface information and access to it is possible, as the nonlinear interaction between the cantilever’s tip and the sample generates a low-frequency heterodyne force that can be detected in the cantilever’s motion, if one tunes this force below its fundamental resonance frequency. A quantitative analysis of the measurements and the determination of their contrast mechanism is only possible with a detailed understanding of the nonlinear dynamics.

We present an experimental and a numerical study of the cantilever motion in HFM, where the two ultrasonic frequencies and the heterodyne frequency are far from any resonance of the cantilever [1,2]. The results provide information on the sensitivity to subsurface features and deliver a recipe for the experimental settings of the frequencies.

[1] G.J. Verbiest et al., Ultramicroscopy 135, 113 (2013)

[2] G.J. Verbiest et al., Nanotechnology 24, 365701 (2013)