Impurity segregation and ordering in Si/ SiO2 / HfO2 structures

We use first-principles calculations and experimental data to demonstrate that impurity segregation at heterointerfaces is governed by several factors. In particular, Hf impurities avoid the Si-SiO2 interface when present in the SiO2 side, might segregate if present in the Si side, but do not cross into SiO2. Substitutional Hf impurities in SiO2, as revealed by a through-focal series of Z -contrast images, act as markers for Si sites, suggesting ordering in the first two Si planes of the amorphous SiO2. Finally, we show that dopants in Si segregate at the interface by adopting several distinct configurations and also do not cross into SiO2.