Effect of Hydrostatic Pressure on Self-interstitial Diffusion in Si, Ge, Si Crystals: Quantum-chemical Simulations

摘要

A theoretical modeling of the diffusion of self-interstitials in silicon and germanium crystals both at normal and high hydrostatic pressure has been carried out using molecular mechanics, semiempirical (PM3, PM5) and ab-initio (SIESTA) methods. According to the simulation for the Si and Ge neutral interstitials (I~0) both in silicon and germanium crystals more stable configuration is <110> split interstitial. T is the stable configuration for the double positive interstitial I~(++), but the interstitial is displaced from the high-symmetry site. Stability of <110> split-interstitial is not changed under hydrostatic pressure. The activation barriers for the diffusion of interstitials were determined and equal to △E_a(Si)(<110> -> T_1)=0.69 eV; △E_a (Ge)(<110> -> T_1)=1.1 eV. For mixed interstitials the calculated activation barriers equal △E_(mix)~(Si)=1.06 eV, △E_(mix)~(Ge) = 0.86 eV. Hydrostatic pressure decreases the activation barriers △E_a(Si), △E_a (Ge).