Abstract
Lateral-force microscopy is a powerful tool to study the frictional properties of two-dimensional materials. However, few works distinctly reveal the correlation between the tip radius with the tip–sample distance and the frictional properties of the two-dimensional (2D) materials. We performed molecular-dynamics simulations to study the atomic-scale friction of a typical two-dimensional single-layer molybdenum disulfide (SLMoS2). The effects of tip radius and tip–sample distance on the frictional properties were analyzed and discussed. The frictional force–sliding-distance curves show typical stick–slip behaviors, and the periodicity can be used to characterize the lattice constants of SLMoS2. Sub-nanoscale stick-slip movements occur in one-lattice sliding periods along with only the armchair (AC) direction and only when the tip radius is smaller than 3 Å with 1.47 Å tip-sample distance. At the same tip–sample distance, a smaller tip can provide a more detailed characterization and higher-precision frictional properties of SLMoS2. A larger tip is capable of providing comparative frictional properties of SLMoS2 at a proper vertical tip–sample distance, compared with the small tip.
Highlights
Among the large family of scanning-probe microscopy techniques, lateral-force microscopy (LFM) is an effective tool to study the atomic-scale frictional behaviors of two-dimensional (2D) materials
Ours is the first study that indicates that the characterization of atomic-scale frictional properties depends on a coupling of tip radius and tip–sample distance, and the study presents novel insight into LFM nanomanipulation when studying the atomic-scale frictional behaviors of 2D materials
The interaction between carbon atoms in the diamond probe is described with the adaptive intermolecular reactive empirical bond-order (AIREBO) (Clemson, SC, US) potential which has been used to predict the mechanical properties of carbon structures in previous studies [25]
Summary
Among the large family of scanning-probe microscopy techniques, lateral-force microscopy (LFM) is an effective tool to study the atomic-scale frictional behaviors of two-dimensional (2D) materials. For the various component forces exerted by sample atoms on the tip such as Van der Waals (dispersion), Coulomb (electrostatic), dipole, and atomic forces, and the shapes of the force curves differing markedly [13], it is difficult to measure the tip–sample distance in the LFM experiments using only the LFM force curves. This approach has resulted in a lack of related studies on the effect of tip–sample distance on frictional properties. Ours is the first study that indicates that the characterization of atomic-scale frictional properties depends on a coupling of tip radius and tip–sample distance, and the study presents novel insight into LFM nanomanipulation when studying the atomic-scale frictional behaviors of 2D materials
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