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O: Fachverband Oberflächenphysik
O 3: Scanning Probe Techniques: Method Development I
O 3.7: Vortrag
Montag, 20. März 2017, 12:00–12:15, TRE Phy
Observation of non-linear dynamics in ultra high vacuum Atomic Force Microscopy — •Daniel Forchheimer1,2, Christian Wagner3, Daniel Platz1, and David Haviland1 — 1Kungliga Tekniska Högskolan, Stockholm, Sweden — 2Intermodulation Products AB, Sweden — 3Peter Grünberg Institute, Jülich, Germany
The tip-surface force in atomic force microscopy goes from being attractive to repulsive as the tip-surface separation change by only a few nano meters. Despite this highly nonlinear force the motion of cantilevers and tuning forks in ultra high vacuum AFMs lack many of the typical signatures of a nonlinear system, such as the the generation of higher harmonics. This is due to the extremely high quality factors of the force probes in vacuum which effectively dampen any off-resonance motion, masking the nonlinear interaction.
We have previously developed Intermodulation AFM for ambient condition, in which the AFM cantilever is excited with two frequencies near a single resonance. We applied such an excitation to a tuning fork AFM in vacuum and could observe the generation of several mixing tones, or intermodulation products, near resonance. These are clear signatures of a nonlinear interaction and by measuring the amplitude and phase at multiple such frequencies we could characterize conservative and dissipative properties of the interaction.