Superlubric sliding in a multi-contact fullerene-molybdenum disulfide heterostructure

Abstract

Recent research shows that superlubric 2D materials offer great potential for friction reduction, yet their requirements of flatness and small scale hinder real-world applications. Here, we study a multi-contact van der Waals heterostructure, composed of fullerene (C₆₀) molecules sandwiched between molybdenum disulfide (MoS₂) atomic layers by molecular-dynamics simulations. We show that despite the multi-contact geometry, the confined layer of C₆₀ nanoparticles exhibits superlubric behavior at high fullerene density or high applied normal force, where the fullerenes’ rotational degrees of freedom are suppressed and the MoS₂ layer slides over the fullerenes. At lower fullerene density or load, fullerene rolling leads to increased frictional dissipation. We demonstrate that the atomic stacking at the fullerene-MoS₂ contact evolves from aligned into misaligned with increasing fullerene coverage, reflecting the increasing fullerene-fullerene interactions suppressing their rolling degrees of freedom. Thus, counterintuitively, in the fullerene-MoS₂ heterojunction system, rolling of the fullerenes is not beneficial for friction reduction, as superlubric slip offers an alternative, lower-friction mechanism. These results on the multi-contact sliding of a heterojunction of fullerene nanoparticles and 2D material are useful for guiding nanoscale superlubric properties into macroscopic scale superlubric applications.