Reinterpretation of velocity-dependent atomic friction: Influence of the inherent instrumental noise in friction force microscopes

Abstract

We have applied both the master equation method and harmonic transition state theory to interpret the velocity-dependent friction behavior observed in atomic friction experiments. To understand the discrepancy between attempt frequencies measured in atomic force microscopy experiments and those estimated by theoretical models, both thermal noise and instrumental noise are introduced into the model. It is found that the experimentally observed low attempt frequency and the transition point at low velocity regimes can be interpreted in terms of the instrumental noise inherent in atomic force microscopy. In contrast to previous models, this model also predicts (1) the existence of a two-slope curve of velocity dependence and (2) the decrease of critical velocity with temperature, which provides clues for further experimental verification of the influence of instrumental noise in friction measurements.

Multiscaling behavior of atomic-scale friction

“…Their study was based on analyzing the noises of nanofriction data using the method of power spectral density and simulating the effect of each of these noises on nanofriction. Furthermore, Dong et al [23,24] considered the effect of thermal and instrumental noises on the theoretical modeling of nanofriction using the master equation method.…”

Dynamics of Atomic Stick-Slip Friction Examined with Atomic Force Microscopy and Atomistic Simulations at Overlapping Speeds

“…In this approach, both noise sources are specified in the model, with the magnitude of the athermal noise vibration to be modeled determined by calibrating its amplitude in the experiment with respect to the amplitude of the cantilever's thermal noise (as determined in a power spectrum of cantilever signal). This analysis indicates that two transition points can occur: a plateau-like reduction in slope at low speed determined by low frequency instrument noise, and a plateau at high speed due to higher frequency thermal noise [43] (Fig. S-8 to an effective temperature of 1800 K based on the equipartition theorem [45], thus, the noise observed in the experiment is likely a combination of the thermal noise from the AFM cantilever oscillating at its first lateral resonance and athermal noise associated with the mechanical vibrations of the AFM apparatus.…”

“…In the PTT model, only those thermal vibrations of the tip apex are considered. However, other thermal noise sources, such as thermally induced vibrations of the cantilever, or athermal instrument noise, such as mechanical vibrations of the AFM apparatus and electronic 60 Hz noise, are not included despite the fact that they too can lower the activation barrier to slip by adding energy into the contact [42,43]. Both athermal and thermal noise sources are inherent in every experiment, but not fully captured in simulations.…”

Imaging high-speed friction at the nanometer scale

“…F noise ( t ) is a random noise force with a Gaussian distribution127. The strength of the noise is characterized by the standard deviation σ noise , given in Table 1.…”