The loading speed facilitating stress relaxation behaviors of surface-modified silicon: a molecular dynamics study

Time-dependent plastic deformation commonly exists in silicon-based microelectronic contact. The stress relaxation behaviors of SiO₂/Si bilayer composite are studied using molecular dynamics simulation by varying loading speed. The results imply that the indentation force decreases sharply at the initial and linearly towards the end of holding, and the amount of stress relaxation increases with the increasing loading speed. The plastic deformation of confined amorphous SiO₂ film is carefully analyzed based on the amorphous plasticity theories; variations of coordinated silicon atoms and Si-O bond number indicate that the films are further densified at different degrees depending upon loading speed during holding. The densification is strengthened at a higher speed because much more activated shear transformation zones (STZs) and accumulated free volume generate within films indented at higher speed. The phase transformation of monocrystalline silicon is observed in indented silicon during holding; the Si-II and bct-5 silicon atoms increase with time and loading speed.