ライス大学の研究者らが、2次元材料に新たな機能を発見 Rice University scientists find new workable feature of a class of 2D materials
2023-03-06 ライス大学
強誘電性材料は、負と正のイオンで構成され、イオンが電荷に基づいて分離することで自発的な偏極を生じる。この新しい特徴は、2D材料のクラスの基本的な特性の発見と、実用的な応用角度の組み合わせである。
今後、この材料は、タービンや電気エンジンをスイッチオン、あるいはアダプティブ光学望遠鏡のミラーを制御するなどのアクチュエーターとして使用される可能性がある。
＜関連情報＞
- https://news.rice.edu/news/2023/bending-2d-nanomaterial-could-switch-future-technologies
- https://pubs.acs.org/doi/10.1021/acsnano.3c00492
二次元単層アクチュエータの強誘電性とワークサイクルについて Flexo-Ferroelectricity and a Work Cycle of a Two-Dimensional-Monolayer Actuator
Jun-Jie Zhang, Tariq Altalhi, and Boris I. Yakobson
ACS Nano Published:February 28, 2023
DOI:https://doi.org/10.1021/acsnano.3c00492
Abstract
Well recognized mechanical flexibility of two-dimensional (2D) materials is shown to bring about unexpected behaviors to the recently discovered monolayer ferroelectrics, especially those displaying normal, off-plane polarization. A “ferro-flexo” coupling term is introduced into the energy expression, to account for the connection of ferroelectricity and bending (strain gradient) of the layer, to predict and quantify its spontaneous curvature and how it affects the phase transitions. With InP as a chemically specific representative example, the first-principles calculations indeed reveal strong coupling ∼P·ϰ between the ferroelectric polarization (P) and the curvature of the layer (ϰ ≡ 1/r), having profound consequences for both mechanics and ferroelectricity of the material. Due to flexural relaxation, the spontaneous polarization and the transition barrier rise significantly, leading to large changes in the Curie temperature, coercive field, and domain wall width and energy, based on Monte Carlo simulations. On the other hand, the polarization switching, characteristic to ferroelectrics, does induce an overall layer bending, enabling a conversion of electrical signal to movement as an actuator; its possible work-cycles and maximum work-efficiency are briefly discussed.
