Tribological characteristics of atomic-scale niobium diselenide grown via chemical vapor deposition

The nanoscale tribological characteristics of atomic-layered niobium diselenide (NbSe2) were investigated using atomic force microscopy (AFM). Two-dimensional NbSe2 atomic layers were produced on a weakly-adherent silicon wafer using two different methods: (1) mechanical exfoliation and (2) controlled synthesis via chemical vapor deposition. Using an AFM cantilever tip, a normal force was applied on the NbSe2 atomic-scale thin films in order to measure friction force. The as-synthesized NbSe2 thin films exhibited atomic lattice stick-slip friction, with the thinnest sheets showing a sliding length-dependent increase in static friction. This tendency is attributed to the increased susceptibility of the thinner chemically-synthesized NbSe2 sheets toward out-of-plane elastic deformation.