【公開日：2024.07.25】【最終更新日：2024.07.25】
課題データ / Project Data
課題番号 / Project Issue Number
23UT0187
利用課題名 / Title
Memristor Devices and Their Neuromorphic Network using Silicon-based Perovskite Oxides
利用した実施機関 / Support Institute
東京大学 / Tokyo Univ.
機関外・機関内の利用 / External or Internal Use
内部利用（ARIM事業参画者以外）/Internal Use (by non ARIM members)
技術領域 / Technology Area
【横断技術領域 / Cross-Technology Area】（主 / Main）計測・分析/Advanced Characterization（副 / Sub）-
【重要技術領域 / Important Technology Area】（主 / Main）高度なデバイス機能の発現を可能とするマテリアル/Materials allowing high-level device functions to be performed（副 / Sub）-
キーワード / Keywords
エレクトロデバイス/ Electronic device,X線回折/ X-ray diffraction
利用者と利用形態 / User and Support Type
利用者名（課題申請者）/ User Name (Project Applicant)
李 海寧
所属名 / Affiliation
東京大学 大学院工学系研究科
共同利用者氏名 / Names of Collaborators in Other Institutes Than Hub and Spoke Institutes
末吉 七海,片岡 莉咲
ARIM実施機関支援担当者 / Names of Collaborators in The Hub and Spoke Institutes
府川 和弘,飯盛 桂子
利用形態 / Support Type
（主 / Main）機器利用/Equipment Utilization（副 / Sub）,技術補助/Technical Assistance
利用した主な設備 / Equipment Used in This Project
UT-203：粉末X線回折装置
UT-202：高輝度In-plane型X線回折装置
UT-305：環境制御マニュアルプローバステーション
報告書データ / Report
概要（目的・用途・実施内容）/ Abstract (Aim, Use Applications and Contents)
Given that HfO2 and ZrO2 are twin oxides owing to their similar crystal structures and physical properties, one would anticipate that ZrO2 could potentially serve as buffer layer as well. However, limited research has been conducted on this aspect. Regarding the rapid deposition, cost reduction, and easily adjustable composition for mass production, spin-coating is a valuable technique. Inspired by the motivations above, we utilized ZrO2 thin films as buffer layers on Si wafers to achieve the epitaxial and single-crystalline growth of Pb(Zr0.52Ti0.48)O3 (PZT) thin films, a widely commercialized ferroelectric material, through a one-step spin-coating process. We also systematically investigated its ferroelectric polarization for future applications as mass-manufactured memristors.
実験 / Experimental
(1) The crystallinity and epitaxial growth of the thin films were evaluated by measuring 2theta-omega, phi scans, and reciprocal lattice mapping using an XRD equipment (SmartLab 3kW).
(2) The thickness of the thin films was measured by an XRD equipment (SmartLab 3kW).
(3) The ferroelectric properties of the thin films was evaluated by a probe system connected to the FCE1EEA-200 instrument.
結果と考察 / Results and Discussion
Figure 1 and 2 presents the XRD 2θ/ω patterns revealing the tetragonal crystal structures of PZT thin films deposited by sputtering and spin-coating methods, respectively. The single crystallinity can result from the absence of extra crystalline impurity phases. All PZT films are highly oriented along the (001) direction, e.g., c-axis direction, along which tetragonal PZT can exhibit the ferroelectric polarization. Figure 3 shows the out-of-plane φ scan of the PZT film and the Si substrate at (022) plane, both of which exhibit four-fold symmetry, which could be attributed to the four domains of PZT (100) and Si (100) epitaxial alignment. The single-crystalline PZT films deposited by sputtered and spin coated are epitaxially grown with a cube-on-cube relationship. There results confirm that PZT films entirely show good single-crystalline properties along c-axis (001) alignment, instead of a-axis (100) alignment. Figure 4 shows the reciprocal space mapping of the (–204) reflection of the PZT and Pt film, as well as the (–206) reflection of Si substrate, which was corresponding well with the previous study. As expected, these results support the epitaxial growth of the spin coated film, as well as the Pt films. The figure also reveals the in-plane epitaxial relationship PZT(100)//Pt(100)//Si(100).
We also applied identical experimental fabrications for the HZO buffer layer, Pt, and bottom electrode SRO film. The PZT films were spin coated and annealed under different temperatures. As shown in Figure 5, spin coated PZT films annealed at 500°C and 700°C exhibit ferroelectric polarization, which become more pronounced with increasing voltages. The ferroelectric polarization loops show the saturated polarization Ps ≈ 40 μC/cm2 for both PZT films annealed at 500°C and 700°C, but remanent polarization Pr ≈ 30 μC/cm2 as well as coercive field in PZT film annealed at 500°C is larger than that of film annealed at 700°C. This indicates that a lower annealing temperature contributes to better ferroelectric polarization.
図・表・数式 / Figures, Tables and Equations
Figure 1. XRD 2θ/ω pattern of sputtered PZT film.
Figure 2. XRD 2θ/ω patterns of spin coated PZT films under different annealing temperatures.
Figure 3. XRD φ scans of (022) plane of sputtered and spin coated PZT(100) and Si (100).
Figure 4. XRD reciprocal space mapping (RSM) of the (–204) reflection of spin coated PZT film and (–206) reflection of Si substrate.
Figure 5. (a, b) Maximum voltage- and (c, d) frequency-dependent ferroelectric loops of PZT film annealed at (a, c) 500°C and (b, d) 700°C.
その他・特記事項（参考文献・謝辞等） / Remarks(References and Acknowledgements)
粉末X線回折装置の測定法を指導していただいた管理人である府川様および飯盛様に感謝しております。
成果発表・成果利用 / Publication and Patents
論文・プロシーディング（DOIのあるもの） / DOI (Publication and Proceedings)
-
Haining Li, Epitaxial Single‐Crystalline PZT Thin Films on ZrO2‐Buffered Si Wafers Fabricated Using Spin‐Coating for Mass‐Produced Memristor Devices, Advanced Electronic Materials, , (2024).
DOI: 10.1002/aelm.202400280
口頭発表、ポスター発表および、その他の論文 / Oral Presentations etc.
- 李海寧，木島健，片岡莉咲，山原弘靖，田畑仁，関宗俊，”Epitaxial Growth of PZT Thin Films on HfO2-Buffered Si Substrates via Spin-coating Technique”，第84回応用物理学会秋季学術講演会，令和5年9月20日
特許 / Patents
特許出願件数 / Number of Patent Applications：0件
特許登録件数 / Number of Registered Patents：0件