Mechanical properties of the nanoscale molecular cluster of water meniscus by high-precision frequency modulation atomic force spectroscopy
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Experiment results on the water meniscus obtained by the QTF-based FM- and AM-AFM system. (a) Approach (blank interior)/retraction (full interior) curves ofthe measured frequency shift (black square) and damping coefficient (red circle) for FM-AFM. Formation position of NMC-WM (i) from the surface (ii) was determined by the full approach at the starting spot of negative frequency shift and saturation of damping coefficient (inset). (b) Measured amplitude and phase changes for AM-AFM. (c) and (d) Comparison of theoretically evaluated elasticity and damping for FM and AM modes. (e) Response time of FM (frequency shift) and AM (amplitude) modes by pulling the NMC-WM back to 2 nm far from the surface at the spot of formation. (f) Noise level of the FM and AM modes.
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Mechanical properties of the NMC-WM according to the increment of the oscillation amplitude in the QTF-based FM-AFM. (a) Approach (blank interior)/retraction (full interior) curves of the measured frequency shift (black square) and damping coefficient (red circle) for the 0.2 nm oscillation amplitude. (b)-(f) Theoretically derived elasticity, damping, elastic force, viscous force, and energy dissipation due to the water meniscus by using the results of the frequency shifts and damping coefficients. As the oscillation amplitude increases, , and increase while and show invariantly similar results.
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