Direct epitaxial growth of polar Hf0.5Zr0.5O2 films on corundum

This article belongs to the Special Issue Pulsed Laser Deposited Nanostructures.Single-phase epitaxial Hf0.5Zr0.5O2 films with non-centrosymmetric orthorhombic structure have been grown directly on electrode-free corundum (α-Al2O3) substrates by pulsed laser deposition. A combination of high-resolution X-ray diffraction and X-ray absorption spectroscopy confirms the epitaxial growth of high-quality films belonging to the Pca21 space group, with [111] out-of-plane orientation. The surface of a 7-nm-thick sample exhibits an atomic step-terrace structure with a corrugation of the order of one atomic layer, as proved by atomic force microscopy. Scanning transmission electron microscopy reveals that it consists of grains with around 10 nm lateral size. The polar nature of this film has been corroborated by pyroelectric measurements. These results shed light on the mechanisms of the epitaxial stabilization of the ferroelectric phase of hafnia.We acknowledge the research projects MAT2017-88788-R, PID2019-107338RB-C64, and PID2020-112914RB-I00, funded by MCIN/AEI/10.13039/501100011033. This work has received funding from regional Gobierno de Aragón through projects E28_20R and E12_20R, including FEDER funding, and from the EU’s Horizon 2020 programme under the grant agreement No. 823717-ESTEEM3 and the Marie Skłodowska-Curie grant agreement No. 861153-MANIC.Peer reviewe