Elucidation of structural properties of ferroelectric domains revealed by in-situ biasing together with microsecond HVEM observation

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H02746
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Nanomaterials engineering
• Research Institution: Osaka University
• Principal Investigator: Sato Kazuhisa 大阪大学, 超高圧電子顕微鏡センター, 准教授 (70314424)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 電場印加 / マイクロ秒観察 / 時間分解 / 超高圧電子顕微鏡 / リラクサー強誘電体

Outline of Final Research Achievements

Ferroelectric materials such as PMN-PT are known as relaxor ferroelectrics characterized by inhomogeneous nanostructures known as polar nano-regions. To elucidate ferroelectric domain switching mechanism, we employed in situ biasing in a high-voltage electron microscope (HVEM) equipped with a direct electron detection (DED) CMOS camera. We developed a novel electrical biasing specimen holder for in situ HVEM observation. The DED camera enables fast image acquisition with a frame rate of 400 fps. Microstructures of the PMN-0.3PT specimens were composed of ferroelectric domains, 100～200 nm in sizes, oriented [110] and [1-10] directions. By applying electric field (1 kV/mm) in the [110] directions, domain switching initiated at a corner of a domain, and propagated rapidly. Domain switching kinetics was analyzed based on the Kolmogolov-Avrami-Ishibashi model and found that the switching proceeds via two-dimensional nucleation and growth (n = 2.4-3.2).

Free Research Field

電子顕微鏡学

Academic Significance and Societal Importance of the Research Achievements

本研究の大きな特徴は、超高圧電子顕微鏡を活用したバルク強誘電体試料の電場印加その場観察にある。実デバイスを模擬したバルク状厚膜試料を用いて、組成相境界近傍における強誘電体ドメイン構造とその電場応答を従来にない1/400秒スケールで可視化した点に学術的意義がある。リラクサー現象の構造物性を明らかにする上で、バルク単結晶に近い厚膜試料を対象とした電場印加高速その場観察法の実現は、統計的信頼性の観点から非常に有用と考えられ、広範な用途を有するリラクサー強誘電体材料開発のための研究手法として今後の発展が期待される。