Molecular dynamics simulation of sphere indentation in a thin copper film

The paper presents simulation results of indentation of a rigid sphere in a thin copper film. In the simulation, we studied two structural states of the film (a defect-free single crystal and a polycrystal with a grain size of several nanometers) and two types of the substrate (a perfectly rigid substrate and single-crystal Al substrate). It is found that the single-crystal film, unlike the polycrystalline one, reveals the scale effect in the dependence of hardness on the indenter radius and penetration depth. The surface roughness of the Cu film retards the increase in load by about the roughness depth. The loading curve is found to depend on the indenter position about the Cu film - Al substrate interface.