Solid state epitaxy of (Hf,Zr)O2 thin films with orthorhombic phase

Takanori Kiguchi, Shogo Nakamura, Akihiro Akama, Takahisa Shiraishi, Toyohiko J. Konno

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Hf0.5Zr0.5O2 (HZO) thin films with orthorhombic phase Pca21 are novel ferroelectric materials. We have attempted the epitaxial growth of HZO thin films using solid-state epitaxy with ion-beam sputtering followed by rapid thermal annealing. X-ray diffraction (XRD) profiles of HZO thin films on SiO2 glass substrates showed {111}-oriented monoclinic and orthorhombic phases. On the other hand, XRD profiles of HZO on yttria stabilized zirconia (YSZ) (100) substrates indicated the shoulder peak on the strong tail of 200 peak of YSZ substrates in the lower 2θ side. Structural analyses of the HZO thin films have conducted to identify constituent phases, the local orientation, and the nanostructure of HZO thin films using aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and the related STEM-EDS analysis. In this paper, we have described the orthorhombic (Pca21) and monoclinic (P21/c) phases coexisted based on multislice image simulation and diffractogram analysis of the local regions in HZO thin films. The principal phase in the HZO/YSZ epitaxial thin films is the orthorhombic phase. Each phase was epitaxially grown on the YSZ substrate with a domain structure of the order of 10nm in size. The orthorhombic phase has formed in the HZO/SiO2 glass thin films, which indicates that the stability of the orthorhombic phase is ascribed to not only pseudomorphic or lattice mismatch effects of the substrate but also doping effects and thermal mismatch between the film and the substrate. The mosaicity of thin film is high because of lattice deformation with coexisting monoclinic phase and a damaged region between thin film and substrate caused by sputtered particles with high energy. Orthorhombic single-phase thin films with higher quality can be obtained by preparing ultrathin HZO epitaxial thin films under lower Ar-ion beam energy in the sputtering process and the higher crystallization temperature in the post-annealing process.

Original languageEnglish
Pages (from-to)689-693
Number of pages5
JournalJournal of the Ceramic Society of Japan
Volume124
Issue number6
DOIs
Publication statusPublished - 2016 Jun

Keywords

  • HAADF-STEM
  • HfO
  • Monoclinic phase
  • Mosaic structure
  • Orthorhombic phase
  • Solid-state epitaxy
  • Thin film
  • ZrO

ASJC Scopus subject areas

  • Ceramics and Composites
  • Chemistry(all)
  • Condensed Matter Physics
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Solid state epitaxy of (Hf,Zr)O<sub>2</sub> thin films with orthorhombic phase'. Together they form a unique fingerprint.

  • Cite this