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MI: Fachverband Mikrosonden
MI 4: Scanning Probe Microscopy
MI 4.2: Vortrag
Dienstag, 1. April 2014, 11:30–11:45, MER 02
Ultrasound plus Heterodyne Detection enables SubSurface sensitivity in an AFM — •Gerard J. Verbiest1 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
Similar to the sonar of a submarine, it is possible to reach subsurface sensitivity with an AFM: it has been demonstrated that 20 nm small nanoparticles can be resolved, even if they are buried 500 nm deep in a sample. To enable this, Heterodyne Force Microscopy uses two ultrasonic signals in the order of a few MHz, which are sent through the cantilever and the sample, respectively. To detect the sample vibration, the ultrasonic frequencies are chosen slightly different to generate a low-frequency heterodyne force via the nonlinear interaction between the cantilever’s tip and the sample. It is this heterodyne signal that contains the subsurface information. However, how this signal is exactly generated is not known.
We developed a general analytical model [1] to quantitatively explain the generation of the heterodyne signal. Standard textbook equations fail in this case, as they are all based on second order approximations. We confirm our results with both an experiment [2] and a full numerical calculation [3] on the example of Heterodyne Force Microscopy.
[1] G.J. Verbiest, and M.J. Rost, Nature Physics submitted
[2] G.J. Verbiest et al., Nanotechnology 24, 365701 (2013)
[3] G.J. Verbiest et al., Ultramicroscopy 135, 113 (2013)