Microstructure and strain rate dependences of plastic deformation in diamond-like carbon films during nanoindentation

•Nanoindentation reveals microstructure and strain rate dependent deformation in DLC films.•The mechanical properties mainly depend on the sp3-C content varying with power.•DLC films show positive sensitivity of hardness to strain rate.•Shear driven reversible hybridization transition makes deformation significant. Despite growing interest in scientific researches and engineering applications of diamond-like carbon (DLC) films, the fundamental deformation mechanisms that govern mechanical properties still remain unclear. In this work, the microstructure and strain rate dependences of plastic deformation in magnetron sputtered DLC films were investigated by employing nanoindentation tests and molecular dynamics simulations. Firstly, the mechanical responses of the films to the varied microstructures with sputtering power were discussed. Then, the underlying deformation mechanisms of the films were identified in terms of the strain rate sensitivity with m in a wide range of 0.038∼0.122. The experimental and calculated results finally revealed that the mechanical behaviors of the films are dependent upon both the initial internal hybridized structures and the external loading conditions. The deformation driven asymmetrically reversible hybridization transition with strain rate sensitivity could be considered as one of the specific atomic-scale mechanisms of the significant plastic deformation in DLC films.