Impurity segregation and ordering inSi/SiO2/HfO2structures

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 ${\text{Si-SiO}}_{2}$ interface when present in the ${\text{SiO}}_{2}$ side, might segregate if present in the Si side, but do not cross into ${\text{SiO}}_{2}$. Substitutional Hf impurities in ${\text{SiO}}_{2}$, 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 ${\text{SiO}}_{2}$. Finally, we show that dopants in Si segregate at the interface by adopting several distinct configurations and also do not cross into ${\text{SiO}}_{2}$.