The effect of set point ratio and surface Young’s modulus on maximum tapping forces in fluid tapping mode atomic force microscopy

Abstract

There is great interest in using proximal probe techniques to simultaneously image and measure physical properties of surfaces with nanoscale spatial resolution. In this regard, there have been recent innovations in generating time-resolved force interaction between the tip and surface during regular operation of tapping mode atomic force microscopy (TMAFM). These tip/sample forces can be used to measure physical material properties of surface in an analogous fashion to the well-established static force curve experiment. Since its inception, it has been recognized that operation of TMAFM in fluids differs significantly from that in air, with one of the major differences manifested in the quality factor (Q) of the cantilever. In air, Q is normally on the order of 200–400, whereas in fluids, it is of the order of approximately 1–5. In this study, we explore the impact of imaging parameters, i.e., set point ratio and free cantilever oscillation amplitude, on time varying tip-sample force interactions in fluid TMAFM via simulation and experiment. The numerical AFM model contains a feedback loop, allowing for the simulation of the entire scanning process. In this way, we explore the impact of varying the Young’s modulus of the surface on the maximum tapping force.