Stabilization of the epitaxial rhombohedral ferroelectric phase in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>ZrO</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> by surface energy

Doped HfO2 and HfO2-ZrO2 compounds are gaining significant interest thanks to their ferroelectric properties in ultrathin films. Here, we show that ZrO2 could be a playground for doping strain engineering increase the thickness epitaxial thin Based on surface energy considerations supported by ab initio calculations, pure film exhibits rhombohedral phase (r-phase, with R3m space group) more stable than Hf0.5Zr0.5O2 (HZO) cases. In particular, up 37 nm experimentally evidence single (111)-oriented r-phase films deposited La2/3Sr1/3MnO3-buffered DyScO3(110) substrate, while tetragonal is observed alongside one SrTiO3(001). The formation of this discussed compared between HfO2, HZO, highlighting role energy.