We show that atomically flat single SrO-terminated ${\text{SrTiO}}_3\left(001\right)$ substrates can be obtained through simple high-temperature treatment. Amplitude-modulation atomic force microscopy with phase-lag analysis and x-ray photoelectron spectroscopy, have been used to demonstrate that the ratio between the two chemical terminations can be tailored by choosing the annealing time. Moreover, the progressive SrO surface enrichment (up to 100%) is accompanied by a self-assembly process which results in the spatial separation at the nanoscale of both chemical terminations. We further demonstrate that this opens a interesting avenue for selective chemical reaction and growth of oxide nanostructures.

SrTiO₃ templates have been used to integrate epitaxial bilayers of ferroelectric Hf_0.5Zr_0.5O₂ and La_2/3Sr_1/3MnO₃ bottom electrodes on Si(001). The Hf_0.5Zr_0.5O₂ films show enhanced properties in comparison to equivalent films on SrTiO₃(001) single crystalline substrates. The films, thinner than 10 nm, have a very high remnant polarization of 34 μC/cm². Hf_0.5Zr_0.5O₂ capacitors at an operating voltage of 4 V present a long retention time well beyond 10 years and high endurance against fatigue up to 10⁹ cycles. The robust ferroelectric properties displayed by the epitaxial Hf_0.5Zr_0.5O₂ films on Si(001) using SrTiO₃ templates pave the way for the monolithic integration on silicon of emerging memory devices based on epitaxial HfO₂.

Epitaxial thin films of HfO₂ doped with La have been grown on SrTiO₃(001) and Si(001), and the impact of the La concentration on the stabilization of the ferroelectric phase has been determined. Films with 2–5 at. % La doping present the least amount of paraelectric monoclinic and cubic phases and exhibit the highest polarization, having a remanent polarization above 20 μC/cm². The dopant concentration results in an important effect on the coercive field, which is reduced with increasing La content. Combined high polarization, high retention, and high endurance of at least 10¹⁰ cycles is obtained in 5 at. % La-doped films.

Ferroelectric BaTiO₃ is rarely used in monolithic Si devices due to the low quality of BaTiO₃ films on Si, as polycrystallinity, degradation of bottom Pt electrodes, low polarization, and high roughness. Here, we overcome these limitations by using a buffer structure that combines yttria-stabilized zirconia, CeO₂, and conducting LaNiO₃. BaTiO₃ films on the multilayered buffer, with total thickness of the buffer below 100 nm, are epitaxial, display remnant polarization of 6–10 μC/cm², and have roughness of a few Å. These unprecedented properties pave the way to integrate ferroelectric BaTiO₃ into Si platforms.