Radial nanofretting behaviors of ultrathin carbon nitride film on silicon substrate

► Radial nanofretting damage on a-CNx film experiences buckling, cracking and detachment of film. ► These damages can be detected by the variation in the apparent contact stiffness. ► The initial increase in the contact stiffness indicates the buckling of film. ► The following sharp decrease reveals the initiation and propagation of circular cracks in film. ► The final stable contact stiffness implies the detachment of film.