A rhombohedral ferroelectric phase in epitaxially strained Hf0.5Zr0.5O2 thin films. Issue 12 (December 2018)

• Record Type: Journal Article
• Authors: Wei, Yingfen; Nukala, Pavan; Salverda, Mart; Matzen, Sylvia; Zhao, Hong; Momand, Jamo; Everhardt, Arnoud; Agnus, Guillaume; Blake, Graeme; Lecoeur, Philippe; Kooi, Bart; Íñiguez, Jorge; Dkhil, Brahim; Noheda, Beatriz
• Is Part Of: Nature materials. Volume 17:Issue 12(2018)
• Page Start: 1095
• Page End: 1100
• Publication Date: 2018-12
• Subjects: Materials science -- Periodicals; Materials -- Technological innovations -- Periodicals; Materials -- Periodicals; 620.1105
• DOI: 10.1038/s41563-018-0196-0
• Languages: English
• ISSNs: 1476-1122

Abstract

Abstract Hafnia-based thin films are a favoured candidate for the integration of robust ferroelectricity at the nanoscale into next-generation memory and logic devices. This is because their ferroelectric polarization becomes more robust as the size is reduced, exposing a type of ferroelectricity whose mechanism still remains to be understood. Thin films with increased crystal quality are therefore needed. We report the epitaxial growth of Hf0.5 Zr0.5 O2 thin films on (001)-oriented La0.7 Sr0.3 MnO3 /SrTiO3 substrates. The films, which are under epitaxial compressive strain and predominantly (111)-oriented, display large ferroelectric polarization values up to 34 μC cm−2 and do not need wake-up cycling. Structural characterization reveals a rhombohedral phase, different from the commonly reported polar orthorhombic phase. This finding, in conjunction with density functional theory calculations, allows us to propose a compelling model for the formation of the ferroelectric phase. In addition, these results point towards thin films of simple oxides as a vastly unexplored class of nanoscale ferroelectrics. Ferroelectric hafnia occurs only in a thin-film orthorhombic phase that needs wake-up cycling to induce ferroelectricity. Here, by growing thin-film Hf0.5 Zr0.5 O2 under strain, a polar rhombohedral phase is achieved that does not require cycling.