Ferroelectric (Hf, Zr, La)O2 films. (December 2022)

• Record Type: Journal Article
• Authors: Song, T.; Estandía, S.; Fina, I.; Sánchez, F.
• Is Part Of: Applied materials today. Volume 29(2022)
• Publication Date: 2022-12
• Subjects: Ferroelectric hafnium oxide -- Epitaxial HfO2 -- HfO2 phases; Materials science -- Periodicals; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1016/j.apmt.2022.101661
• Languages: English
• ISSNs: 2352-9407

Abstract

Highlights: The map of phases and polarization in the Hf-Zr-La oxide system has been established with epitaxial films. The optimal La concentration decreases with the Zr content, from 2 to 5% in HfO2 films to 0% in ZrO2 films. Films in the Hf-Zr-La oxide system with optimal dopants concentration have remanent polarization close to 30 μC/cm2, the expected for (111)-oriented pure orthorhombic films. Abstract: The impact of La, Zr and Hf content on the crystal phases and ferroelectric and dielectric properties of (Hf, Zr, La)O2 has been determined by investigating epitaxial films. The polarization of La-doped Hf1-x Zrx O2 films strongly depends on La and Zr content, with remanent polarization ranging from 0 to about 30 µC/cm 2 . The optimal La doping in Hf1-x Zrx O2 increases from 0% to 2–5% for decreasing the Zr content from 100% (ZrO2 ) to 0% (HfO2 ). Structural characterization and dielectric permittivity measurements point to the correlation between crystal phases and polarization. In ZrO2 films, an orthorhombic/tetragonal phase mixture likely evolves into a monoclinic/cubic/tetragonal phase mixture as La doping increases. In films with Hf content, when La content increases, the phases present in Hf0.5 Zr0.5 O2 progressively evolve from orthorhombic and monoclinic to cubic, and in HfO2 from monoclinic, to orthorhombic, and finally to cubic. This map of phases and polarization in the Hf-Zr-La oxide, established with epitaxial films, can be a model system for polycrystalline samples. Graphical abstract: Color map of Pr as a function of Zr and La content Image, graphical abstract