Symmetry Engineering of Epitaxial Hf0.5Zr0.5O2 Ultrathin Films

Arnab De, Min Hyoung Jung, Young Hoon Kim, Seong Bin Bae, Seung Gyo Jeong, Jin Young Oh, Yeongju Choi, Hojin Lee, Yunseok Kim, Taekjib Choi, Young Min Kim, Sang Mo Yang, Hu Young Jeong, Woo Seok Choi

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Robust ferroelectricity in HfO2-based ultrathin films has the potential to revolutionize nonvolatile memory applications in nanoscale electronic devices because of their compatibility with the existing Si technology. However, to fully exploit the potential of ferroelectric HfO2-based thin films, it is crucial to develop strategies for the controlled stabilization of various HfO2-based polymorphs in nanoscale heterostructures. This study demonstrates how substrate-orientation-induced anisotropic strain can engineer the crystal symmetry, structural domain morphology, and growth orientation of ultrathin Hf0.5Zr0.5O2 (HZO) films. Epitaxial ultrathin HZO films were grown on the heterostructures of (001)- and (110)-oriented La2/3Sr1/3MnO3/SrTiO3 (LSMO/STO) substrate. Various structural analyses revealed that the (110)-oriented substrate promotes a higher degree of structural order (crystallinity) with improved stability of the (111)-oriented orthorhombic phase (Pca21) of HZO. Conversely, the (001)-oriented substrate not only induces a distorted orthorhombic structure but also facilitates the partial stabilization of nonpolar phases. Electrical measurements revealed robust ferroelectric properties in epitaxial thin films without any wake-up effect, where the well-ordered crystal symmetry stabilized by STO(110) facilitated better ferroelectric characteristics. This study suggests that tuning the epitaxial growth of ferroelectric HZO through substrate orientation can improve the stability of the metastable ferroelectric orthorhombic phase and thereby offer a better understanding of device applications.

Original languageEnglish
Pages (from-to)27532-27540
Number of pages9
JournalACS Applied Materials and Interfaces
Volume16
Issue number21
DOIs
StatePublished - May 29 2024
Externally publishedYes

Keywords

  • HfO-based ultrathin films
  • crystallographic orientation
  • epitaxial HfO thin film
  • ferroelectricity
  • symmetry engineering

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