Monolayer NbSe 2 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) NbSe (∼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) NbSe, ML NbSe 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 NbSe and the substrate is larger than that of the topmost layer to the underlying layers of NbSe with two or more layers, which can be used to explain that the ML NbSe favors ultralow friction and super wear resistance.