Multi-frequency tapping-mode atomic force microscopy beyond three eigenmodes in ambient air.
We present an exploratory study of multimodal tapping-mode atomic force microscopy driving more than three cantilever eigenmodes. We present tetramodal (4-eigenmode) imaging experiments conducted on a thin polytetrafluoroethylene (PTFE) film and computational simulations of pentamodal (5-eigenmode) cantilever dynamics and spectroscopy, focusing on the case of large amplitude ratios between the fundamental eigenmode and the higher eigenmodes. We discuss the dynamic complexities of the tip response in time and frequency space, as well as the average amplitude and phase response. We also illustrate typical images and spectroscopy curves and provide a very brief description of the observed contrast. Overall, our findings are promising in that they help to open the door to increasing sophistication and greater versatility in multi-frequency AFM through the incorporation of a larger number of driven eigenmodes, and in highlighting specific future research opportunities.
Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States; current address: Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052, United States ; Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, United States.
Santiago D
SD
Solares
Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, United States ; Center for Nanoscale Science and Technology, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States.
Sangmin
S
An
Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, United States ; Center for Nanoscale Science and Technology, National Institute of Standards and Technology (NIST), Gaithersburg, Maryland 20899, United States.
Christian J
CJ
Long
amplitude-modulation; bimodal; frequency-modulation; multi-frequency atomic force microscopy; multimodal; open loop; trimodal