Monolayer NbSe₂ Favors Ultralow Friction and Super Wear Resistance

The urgent demand for atomically thin, superlubricating, and super wear-resistant materials in micro/nanoelectromechanical systems has stimulated the research of friction-reducing and antiwear materials. However, the fabrication of subnanometer-thick films with superlubricating and super wear-resistant properties under ambient conditions remains a huge challenge. Herein, high-quality monolayer (ML) NbSe₂ (∼0.8 nm) with ultralow friction and super wear resistance in an atmospheric environment was successfully grown by chemical vapor deposition (CVD) for the first time. Moreover, compared with few-layered (FL) NbSe₂, ML NbSe₂ has a lower friction coefficient and better wear resistance. On the basis of density function theory (DFT) calculations, the adhesion and the degree of charge transfer between ML NbSe₂ and the substrate is larger than that of the topmost layer to the underlying layers of NbSe₂ with two or more layers, which can be used to explain that the ML NbSe₂ favors ultralow friction and super wear resistance.