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