Exploring the tip-sample interaction regimes in the presence of hysteretic forces in the tapping mode atomic force microscopy

Abstract

In this article, the tip-sample interaction regimes in the presence of hysteretic forces are investigated using atomic force microscopy in the tapping mode. For this purpose, two samples that cause the formation of hysteretic forces, namely, silicon (stiff sample) with an adsorbed water film and polyethylene (compliant sample), are used. Also, for deriving the equation of motion of the microcantilever, the continuous beam model is used, and for determining the contact forces, depending on the sample under investigation, the Derjaguin–Muller–Toporov and Johnson–Kendall–Roberts contact mechanics models are used. The results indicate that the hysteretic interaction forces generate high-periodic and irregular responses at certain tip-sample separation distances. In fact, at these distances, a family of steady-state attractors is found that can be observed in one branch on the minimum tip-sample separation curves and in two separate branches on the average force curves. The reason for this occurrence might be the alternate formation of a liquid column between the probe tip and the sample (in the presence of ambient moisture), and for the compliant sample, the reason might be the alternate formation of an adhesion neck. In this article, the role of hysteretic forces in producing the hysteresis of the amplitude-separation curves is also explored.

Heterogeneous Dissipation and Size Dependencies of Dissipative Processes in Nanoscale Interactions

“…Nanoscale heterogeneity may influence phase transformations, provide materials with nucleation sites for the evolution of processes, , and even drive the self-repairing mechanisms involved in biomolecular processes such as ductility enhancement, damage evolution, and toughening . The interest in these studies is becoming more general and broader, and it is leading to a true understanding of macroscopic and biological phenomena from nanoscale and molecular points of view. − Due to its versatility, − atomic force microscopy (AFM) has recently been employed in several studies to determine the heterogeneity of samples in terms of variations in the dissipative channels ,,,, sometimes utilizing higher modes of vibration in liquid. , The reconstruction and understanding of the dissipative terms however is particularly challenging partly due to the presence of hysteretic interactions that might relate to capillary effects or chemical affinity, ,− artifacts related to the feedback and/or control system, the overall presence of processes that are intrinsically challenging, stochastic, or might include several possible mechanisms, ,, and the fact that the nature of friction in the nanoscale is still relatively unknown and controversial . Thus, it could be argued that these difficulties legitimate the continuous efforts in both theoretical ,, and experimental studies of nanoscale dissipation. ,, …”

Single cycle and transient force measurements in dynamic atomic force microscopy

“…Other than viscous forces, hysteretic forces are typically discussed in the literature. 101,117 Hysteretic forces introduce ambiguity in terms of (2) since in these cases a single force cannot be dened at a given distance. More thoroughly, in the presence of hysteresis the tip-sample system is, by denition, metastable and dissipation will occur even in the absence of viscosity.…”

Energy dissipation in the presence of sub-harmonic excitation in dynamic atomic force microscopy

“…Finally, while an FFT will produce a single DC value z 0 ( fig. 1(b)) and the corresponding frequency contributions (see (15)), it could be argued that the mean deflection z 0 could significantly vary during a single fundamental SH period. Such phenomena might be used together with recent advances in dynamic AFM [29] theory to directly calculate the force and frequency shift produced by d off /d on mechanisms involved with SH excitation.…”

“…Note that while (1) is only valid when driving at the natural frequency of oscillation ω = ω 0 , a simple modification leads to the general solution for any drive frequency ω [13]; ω and ω 0 are the drive and natural angular frequencies, respectively. Equation (1) has been widely used to identify [1] and quantify [3,11,14,15] energy dissipation processes, and, in particular, dissipation processes where capillary interactions are involved [3,14,15]. Still, in one of the first studies of capillary interactions in 56002-p1…”

“…Sub-harmonic (SH) excitation might occur, for example, in the presence of hysteretic forces where the onset of the force occurs on tip approach at a tip-sample distance d on and the breakoff occurs on tip retraction at a distance d off and where d off > d on [16,17]. A common example where this occurs is when the capillary force is present [14][15][16][17][18]. An example of the type of tip-sample force F ts dependencies on tip-sample distance d which might arise in the presence of capillary interactions is given in fig.…”