Gas Modulation Induced Ultra‐Low Friction and Ultra‐Strong Wear Resistance in Atomically Thin MoSe ₂ Single Crystals

Abstract Atomically thin films exhibiting ultra‐low friction and ultra‐strong wear resistance are crucial for overcoming lubrication challenges in micro‐nano electromechanical systems (M/NEMS). However, achieving these properties under conventional pressure conditions remains a major challenge. In this study, a novel strategy is presented to further reduce friction and enhance wear resistance by tuning the atmosphere composition. High‐quality monolayer (ML, ≈0.9 nm) and bilayer (BL) MoSe ₂ single crystals are successfully synthesized via the chemical vapor deposition (CVD) method. Compared to BL MoSe ₂ , ML MoSe ₂ exhibits ultra‐low coefficient of friction (COF = 0.0091) and super wear resistance (40 000 cycles@2.17 GPa) under atmospheric conditions. Additionally, the surface friction can be modulated by varying the oxygen‐to‐nitrogen ratio, and the best friction reduction and anti‐wear properties are achieved in pure nitrogen. Notably, the COF of ML MoSe ₂ can be further reduced by 50% (COF = 0.004), and the wear resistance increases nearly four times (208,640 cycles@2.26 GPa) in pure N ₂ . Experimental and molecular dynamics analyses reveal that stronger adhesion of N ₂ molecules to the surface, coupled with weaker intermolecular interactions, promotes ultra‐low friction and super wear‐resistance in ML MoSe ₂ . The molecular mechanism proposed by this work provides a new degree of freedom for friction modulation and also introduces a promising strategy in constructing ultra‐low friction and super wear‐resistant systems with atomic‐scale thickness.