Characterizing the Free and Surface-Coupled Vibrations of Heated-Tip Atomic Force Microscope Cantilevers
Jason P. Killgore, Ryan C. Tung, Donna C. Hurley
Combining heated-tip atomic force microscopy (HT-AFM) with quantitative methods for determining surface mechanical properties creates an avenue for nanoscale thermomechanical property characterization. For nanomechanical methods that employ an atomic force microscope cantilevers vibrational modes, it is essential to understand how the vibrations of the U-shaped HT-AFM cantilever differ from those of a more traditional rectangular lever, for which analysis techniques are better developed. Here we show, with a combination of finite element analysis and experiments, that the HT-AFM cantilever exhibits many more readily excited vibrational modes over typical AFM frequencies compared to a rectangular cantilever. Opportunities for tapping mode and contact resonance HT-AFM are discussed, with particular emphasis on contact resonance operation. The U- shaped HT-AFM cantilevers exhibit both in-phase and out-of-phase vibrations. The in-phase vibrations are qualitatively similar to flexural vibrations in rectangular cantilevers and generally show increased sensitivity to surface stiffness changes compared to the out-of-phase vibrations. Vibration types can be identified from their frequency and by considering vibration amplitude in the horizontal and vertical channels of the AFM at different laser spot positions on the cantilever. For identifying contact-resonance vibration types, we also consider the sensitivity of the resonance frequencies to a change in applied force and hence contact stiffness. Finally, we assess how existing and new analytical models can be used to accurately predict contact stiffness from contact resonance HT-AFM results. A new model with an added point mass outperforms simpler models that have been widely used to analyze contact resonance data from rectangular cantilevers. By providing insight into cantilever vibrations and limitations of current analysis techniques, our results lay the groundwork for future use of HT-AFM c
, Tung, R.
and Hurley, D.
Characterizing the Free and Surface-Coupled Vibrations of Heated-Tip Atomic Force Microscope Cantilevers, Nanotechnology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915425
(Accessed February 26, 2024)