Avalanche Dynamics in Stick-Slip Cutting of Molybdenum Disulfide

TL;DR

This study reveals nanoscale avalanche dynamics during stick-slip wear of MoS2, combining AFM experiments and molecular dynamics simulations to understand the physical mechanisms of friction and wear in layered materials.

Contribution

First observation of avalanche dynamics at the nanoscale in MoS2 wear, supported by experiments and simulations, providing new insights into nanoscale friction and wear mechanisms.

Findings

Avalanche signatures observed in high-force slip phases.

Molecular dynamics simulations reproduce experimental trends.

Only 20% of energy causes irreversible surface damage.

Abstract

We have investigated nanoscale wear on multilayered MoS2, the flagship transition metal dichalcogenide, by elastically driving sharp diamond tips under normal loads sufficient to induce in-plane fracture. The accompanying friction and the resulting wear structures were first characterized by atomic force microscopy (AFM), revealing a stick-slip regime that drives progressive exfoliation of MoS2 chips. At high normal forces, the slip phase displays hallmark signatures of avalanche dynamics, observed for the first time at the nanoscale, evidenced by a Generalized Extreme Value distribution of friction force drops. The AFM characterization is corroborated by molecular dynamics simulations, which reproduce experimental trends and uncover atomistic details of the wear process, including local amorphization, layer curving, and the involvement of distinct dissipative channels. Notably, it appears that only one-fifth of the energy inputted into the system is used to damage the MoS2 surface irreversibly. These results offer new insight into the physical mechanisms governing friction and wear in layered solids and provide a framework for precision cutting and nanomachining in van der Waals materials, relevant to next-generation devices at sub-micrometer scales.