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Ferroelectric ZrO₂ Monolayers as Buffer Layers between SrTiO₃ and Si
- Dogan, Mehmet, Ismail-Beigi, Sohrab
- Journal of physical chemistry 2019 v.123 no.24 pp. 15053-15061
- energy, oxygen, physical chemistry, silicon, strontium, zirconium oxide
- A monolayer of ZrO₂ 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. 2018, 18, 241–246]. In our previous computational study, we reported on the multiple (meta)stable configurations of ZrO₂ 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, J. Phys. Chem. C 2019 DOI: 10.1021/acs.jpcc.9b01073]. In the current study, we conduct a density functional theory-based investigation of (i) the effect of the 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, for example, SrTiO₃. We find that (i) total energy versus polarization behavior of the monolayers, as well as interface chemistry, is highly dependent on the oxygen content; and (ii) SrTiO₃/ZrO₂/Si stacks exhibit multiple (meta)stable configurations and polarization profiles, that is, zirconia monolayers can induce ferroelectricity in oxides such as SrTiO₃ when used as a buffer layer. This may enable robust nonvolatile device architecture, where the thickness of the gate oxide (here, strontium titanate) can be chosen according to the desired properties.