Structure and dynamics of Ge in the Si-Si O2 system: Implications for oxide-embedded Ge nanoparticle formation

Using gradient corrected periodic density functional theory calculations, we have investigated the structure, energetics, bonding, and diffusion of Ge in bulk α -quartz and amorphous a-Si O2 matrices as well as at the Si (001) a-Si O2 interface. Our calculations show that Ge atoms undergo migration in a-Si O2 with a moderate barrier (<2.5 eV) and prefer to remain in the Si part near the Si (001) a-Si O2 interface via site exchange reaction with Si lattice atoms, while the kicked-out Si atoms are preferentially incorporated into the a-Si O2 matrix. We also discuss implications of the Ge-Si exchange process for Ge nanoparticle formation in an oxide matrix.