Ab-Initio Modeling of Point Defects, Impurities and Diffusion in Silicon

We have revisited the first-principles calculation of the diffusion coefficient for nitrogen monomers and dimers, both within the dissociative and the direct pair-diffusion picture, using density-functional theory and harmonic transition-state theory. From our current understanding, it seems that the results for the dissociative mechanism are in better agreement with experiment than those for the direct pair-diffusion mechanism. Based on a monomer diffusion coefficient of D(T) = 7.3e-3 exp[-0.53 eV/(kT)] cm^2/s, we calculate for the dissociation diffusion parameter of the dimer P = 1.6e9 exp[-2.4 eV/(kT)] cm^(1/2)s

Characterization and Modeling of Atomically Sharp Perfect Si:Ge/SiO_2 Interfaces

Using ab-initio calculations and atomic-resolution Z-contrastimag-ing and electron energy-loss spectroscopy, we show thatoxidation of a germanium-implanted Si surface can produce anatomically-sharp interface with a band structure that seems tobe more favor-able for use in electronic devices than theusually diffuse interface in Si/SiO_2. Furthermore, wepropose an ab-initio based Monte-Carlo model to simulateoxidation of SiGe alloys to better under-stand the formation ofthe sharp interface