Mechanism of field-enhanced friction at MoS₂ atomic steps: Surface potential corrugation, charge-carrier accumulation, and energy barriers

Atomic step is a common defect structure in crystals that contributes major friction origin to lubricant coatings. However, frictional evolution of atomic steps under an electric field remains to be rarely revealed. In this study,
nanofriction properties of MoS2 atomic steps in MoS2/graphene van der Waals heterostructure are studied. The friction forces of the MoS2 steps exhibit an unsymmetric increasing trend under positive and negative electric
fields. A series of specific peaks of surface potential at the MoS2 steps are observed under electric fields, which is consistent with an increase of charge carrier concentration and related to extra sliding energy barriers. This study provides an insight into the nanoscale friction behavior of atomic edge steps and helps to guide the design of contact-electrification systems.