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Ferroelectric Behavior in Exfoliated 2D Aurivillius Oxide Flakes of Sub‐Unit Cell Thickness
Advanced Electronic Materials ( IF 5.3 ) Pub Date : 2020-01-30 , DOI: 10.1002/aelm.201901264 Lynette Keeney 1 , Ronan J. Smith 2 , Meghdad Palizdar 3 , Michael Schmidt 1 , Andrew J. Bell 3 , Jonathan N. Coleman 2 , Roger W. Whatmore 4, 5
Advanced Electronic Materials ( IF 5.3 ) Pub Date : 2020-01-30 , DOI: 10.1002/aelm.201901264 Lynette Keeney 1 , Ronan J. Smith 2 , Meghdad Palizdar 3 , Michael Schmidt 1 , Andrew J. Bell 3 , Jonathan N. Coleman 2 , Roger W. Whatmore 4, 5
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Ferroelectricity in ultrasonically exfoliated flakes of the layered Aurivillius oxide Bi5Ti3Fe0.5Co0.5O15 with a range of thicknesses is studied. These flakes have relatively large areas (linear dimensions many times the film thickness), thus classifying them as 2D materials. It is shown that ferroelectricity can exist in flakes with thicknesses of only 2.4 nm, which equals one‐half of the normal crystal unit cell. Piezoresponse force microscopy (PFM) demonstrates that these very thin flakes exhibit both piezoelectric effects and that the ferroelectric polarization can be reversibly switched. A new model is presented that permits the accurate modeling of the field‐on and field‐off PFM time domain and hysteresis loop responses from a ferroelectric during switching in the presence of charge injection, storage, and decay through a Schottky barrier at the electrode–oxide interface. The extracted values of spontaneous polarization, 0.04(±0.02) C m−2 and electrostrictive coefficient, 2(±0.1) × 10−2 m4 C−2 are in good agreement with other ferroelectric Aurivillius oxides. Coercive field scales with thickness, closely following the semi‐empirical scaling law expected for ferroelectric materials. This constitutes the first evidence for ferroelectricity in a 2D oxide material, and it offers the prospect of new devices that might use the useful properties associated with the switchable ferroelectric spontaneous polarization in a 2D materials format.
中文翻译：
亚单位晶胞厚度的剥落二维二维氧化金片中的铁电行为
层状金刚砂Bi 5 Ti 3 Fe 0.5 Co 0.5 O 15的超声剥落薄片中的铁电厚度范围的研究。这些薄片的面积较大（线性尺寸是薄膜厚度的许多倍），因此将其分类为2D材料。结果表明，铁电可以存在于厚度仅为2.4 nm的薄片中，相当于普通晶体晶胞的一半。压电响应显微镜（PFM）表明，这些非常薄的薄片既显示压电效应，又可逆地切换铁电极化。提出了一个新模型，该模型可以在存在电荷注入，存储和通过电极处的肖特基势垒衰减的情况下，对铁电的场导和场离PFM时域以及磁滞回线响应进行精确建模，氧化物界面。自发极化的提取值0.04（±0.02）C m-2和电致伸缩系数2（±0.1）×10 -2 m 4 C -2与其他铁电Aurivillius氧化物非常吻合。矫顽场随厚度缩放，严格遵循铁电材料的半经验缩放定律。这构成了2D氧化物材料中铁电的第一个证据，它为新设备提供了前景，该设备可能会使用与2D材料格式中的可切换铁电自发极化相关的有用特性。
更新日期：2020-03-09
中文翻译：
亚单位晶胞厚度的剥落二维二维氧化金片中的铁电行为
层状金刚砂Bi 5 Ti 3 Fe 0.5 Co 0.5 O 15的超声剥落薄片中的铁电厚度范围的研究。这些薄片的面积较大（线性尺寸是薄膜厚度的许多倍），因此将其分类为2D材料。结果表明，铁电可以存在于厚度仅为2.4 nm的薄片中，相当于普通晶体晶胞的一半。压电响应显微镜（PFM）表明，这些非常薄的薄片既显示压电效应，又可逆地切换铁电极化。提出了一个新模型，该模型可以在存在电荷注入，存储和通过电极处的肖特基势垒衰减的情况下，对铁电的场导和场离PFM时域以及磁滞回线响应进行精确建模，氧化物界面。自发极化的提取值0.04（±0.02）C m-2和电致伸缩系数2（±0.1）×10 -2 m 4 C -2与其他铁电Aurivillius氧化物非常吻合。矫顽场随厚度缩放，严格遵循铁电材料的半经验缩放定律。这构成了2D氧化物材料中铁电的第一个证据，它为新设备提供了前景，该设备可能会使用与2D材料格式中的可切换铁电自发极化相关的有用特性。
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