  A monolayer of ZrO$_{2}$ has recently been grown on the Si(001) surface and
shown to have ferroelectric properties, which signifies the realization of the
lowest possible thickness in ferroelectric oxides [M. Dogan et al., Nano Lett.,
18 (1) (2018)]. In our previous computational study, we reported on the
multiple (meta)stable configurations of ZrO$_{2}$ monolayers on Si, and how
switching between a pair of differently polarized configurations may explain
the observed ferroelectric behavior of these films [M. Dogan and S.
Ismail-Beigi, arXiv:1902.01022 (2019)]. In the current study, we conduct a
DFT-based investigation of (i) the effect of oxygen content on the ionic
polarization of the oxide, and (ii) the role of zirconia monolayers as buffer
layers between silicon and a thicker oxide film that is normally paraelectric
on silicon, e.g. SrTiO$_{3}$. We find that (i) total energy-vs-polarization
behavior of the monolayers, as well as interface chemistry, is highly dependent
on the oxygen content; and (ii) SrTiO$_{3}$/ZrO$_{2}$/Si stacks exhibit
multiple (meta)stable configurations and polarization profiles, i.e. zirconia
monolayers can induce ferroelectricity in oxides such as SrTiO$_{3}$ when used
as a buffer layer. This may enable a robust non-volatile device architecture
where the thickness of the gate oxide (here strontium titanate) can be chosen
according to the desired properties.
