Quasi-continuum Simulations Of Nanoindentation Of Cu Single Crystal And Shear Deformation Of Twins

Metallic films at nano-scale are widely used in microelectronic mechanical systems(MEMS).Due to its good electrical conductivity,good heat dissipation,strong anti-electromigration ability and high melting point,copper nano-films are becoming interconnection materials in MEMS components.Moreover,by introducing copper twins into the films,the combination properties will be obtained.However,nano-films exhibit special mechanical properties that are quite different from macroscopic cases due to the small size effect Therefore,it is very important to study the mechanical properties of the copper nano thin film in order to improve the performance of MEMS components.In this paper,the quasi-continuum method is used to simulate the initial plastic deformation process of single-crystal copper under nano-indentation.The films with different thickness are selected in the simulations,the load displacement curves,strain energy-displacement curves,and microscopic deformation mechanism are analyzed Secondly,the quasi-continuum method is also used to simulate the shear deformation process of copper twins,and loading force-strain curve and microstructure atom stacking are also analyzed The research has drawn the following results.In the process of nano-indentation,except for the elastic stages,there are severally sudden drop of load which is caused by the dislocation emission nucleation.Without considering the influence of the boundary conditions on the simulations,the size effect of the material is obvious when the size of the material is larger than the size of the indenter,but the thickness of the film has little effect on the nano-hardness of the material.In the process of shear deformation of twins,in addition to the monotonously increasing stage of the elastic properties of the crystal,there is a decreasing period of inelastic properties that resulting from the changes in the interface.When the atomic stacking orientation of crystal and the direction of shear are acute,atomic migration is more likely to occur.