Analysis elastic??plastic behaviour and anisotropy properties of copper film from nanoindentation using numerical computation method

The determination of mechanical properties of nanoscale structures is becoming increasingly important as micro-system and ultra-large-scale integrated circuit technologies continue to mature. Traditional experimental methods cannot avoid the influence on the hardness measurement from the presence of the substrate. Numerical computation method of finite-element modelling with molecular dynamics simulation is used to determine the mechanical properties of copper thin film from indentation, quantifying the difference between load against displacement-into-surface curves obtained from different length scale. The results show that the materials deformation exhibits strong size dependence when the relevant physical length scales fall into the range of microns or below. The P-H graph justifies that the permanent plastic deformation quickly decreased while the elastic deformation gradually increased in the range of nanometre level which means increasing of material microhardness. The different deformation behaviour of crystal layers inside the films may be the potential key factor of its breaking off from the substrate. There is little anisotropy phenomenon in the elastic deformation stage whereas there is obvious anisotropy phenomenon in the plastic deformation process. The anisotropy of thin film has strict preferred orientation distribution and symmetry. The anisotropy deformation gradually minimised accompanying the increasing of plastic deformation illuminates the copper thin film is a nonlinear anisotropy elastic-plastic material.