Elucidation of Phase Stability and Novel Fluorite Type Ferroelectric Phase Thin Films by Controlling Stress Induced Phase Transition

2017 Fiscal Year Final Research Report

• Project/Area Number: 16K14378
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Inorganic materials/Physical properties
• Research Institution: Tohoku University
• Principal Investigator: Takanori Kiguchi 東北大学, 金属材料研究所, 准教授 (70311660)
• Co-Investigator(Kenkyū-buntansha): 白石 貴久 東北大学, 金属材料研究所, 助教 (50758399)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: 蛍石型強誘電体 / ハフニア / ジルコニア / 直方晶相 / 極性構造 / 相安定性 / 応力誘起変態 / ドメイン構造

Outline of Final Research Achievements

Recently, HfO2-based novel phase without spatial symmetry, which is interesting ferroelectric material as Pb-free and non-perovskite-type structure. Hf0.5Zr0.5O2 (HZO) thin films are one of the representative materials with the orthorhombic phase Pca21 in the wide compositional range. We have attempted and realized the epitaxial growth of HZO thin films with the orthorhombic phase Pca21 using solid-state epitaxy with ion-beam sputtering followed by rapid thermal annealing. We have also described the nanoscale morphology and the domain structure of orthorhombic (Pca21) and coexisting monoclinic (P21/c) phases in HZO thin films using the aberration-corrected scanning transmission electron microscopy. These results indicate that two effects, the solute and the elastic constraint effects, are necessary for the stabilization of the orthorhombic phase.

Free Research Field

無機材料物性、結晶工学、電子顕微鏡学