Effective AFM cantilever tip size: methods for in-situ determination

Abstract

In atomic force microscopy (AFM) investigations, knowledge of the cantilever tip radius R is essential for the quantitative interpretation of experimental observables. Here we propose two techniques to rapidly quantify in-situ the effective tip radius of AFM probes. The first method is based on the strong dependency of the minimum value of the free amplitude required to observe a sharp transition from attractive to repulsive force regimes on the AFM probe radius. Specifically, the sharper the tip, the smaller the value of free amplitude required to observe such a transition. The key trait of the second method is to treat the tip–sample system as a capacitor. Provided with an analytical model that takes into account the geometry of the tip–sample’s capacitance, one can quantify the effective size of the tip apex fitting the experimental capacitance versus distance curve. Flowchart-like algorithms, easily implementable on any hardware, are provided for both methods, giving a guideline to AFM practitioners. The methods’ robustness is assessed over a wide range of probes of different tip radii R (i.e. 4 < R < 50 nm) and geometries. Results obtained from both methods are compared with the nominal values given by manufacturers and verified by acquiring scanning electron microscopy images. Our observations show that while both methods are reliable and robust over the range of tip sizes tested, the critical amplitude method is more accurate for relatively sharp tips (4 nm < R < 10 nm).

Controlled tip wear on high roughness surfaces yields gradual broadening and rounding of cantilever tips

“…These tools are based on in situ EM13, surface topography spectral analysis17, cantilever dynamics2425 or the capacitor function of the tip-sample system25. With this study we have added a method to the currently available toolbox, in particular we added a method for fast in situ tip size determination based on statistical analysis of peaks in AFM images.…”

Characterization of Frictional Properties of Single-Layer Molybdenum-Disulfide Film Based on a Coupling of Tip Radius and Tip–Sample Distance by Molecular-Dynamics Simulations

“…This ability allows for atom-specific-force mapping with piconewton and picometer resolution [ 1 , 2 ]. Because experimental LFM measurements are affected by interatomic interactions between the probe tip and the sample surface [ 3 ], the tip features, including its stiffness [ 4 ], asymmetry [ 5 , 6 ], apex structure [ 7 , 8 ], and chemical identity [ 9 , 10 ], are important in lateral-force imaging of surfaces and the characterization of frictional behaviors at the atomic scale. In general, scanning-probe microscopy/LFM measurements are thought to be more accurate with a sharper tip [ 11 , 12 ].…”

Built-up AFM tips by metal nanoclusters engineering

“…Finally, it is worth to mention methods that could be used to characterize the size of the grown cluster nanotips. References [38][39][40] describe methodologies to determine the tip size. So far, these methods have been applied to AFM in atmospheric condition working in the amplitude modulation mode.…”