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Layer-dependent ferroelectricity in 2H-stacked few-layer α-In2Se3
Materials Horizons ( IF 12.2 ) Pub Date : 2020-12-10 , DOI: 10.1039/d0mh01863e
Baohua Lv 1 , Zhi Yan , Wuhong Xue , Ruilong Yang , Jiayi Li , Wenjuan Ci , Ruixue Pang , Peng Zhou , Gang Liu , Zhongyuan Liu , Wenguang Zhu , Xiaohong Xu
Materials Horizons ( IF 12.2 ) Pub Date : 2020-12-10 , DOI: 10.1039/d0mh01863e
Baohua Lv 1 , Zhi Yan , Wuhong Xue , Ruilong Yang , Jiayi Li , Wenjuan Ci , Ruixue Pang , Peng Zhou , Gang Liu , Zhongyuan Liu , Wenguang Zhu , Xiaohong Xu
Affiliation
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Atomically thin two-dimensional (2D) van der Waals materials have exhibited many exotic layer-dependent physical properties including electronic structure, magnetic order, etc. Here, we report a striking even–odd layer dependent oscillation in the ferroelectric polarization of 2H-stacked few-layer α-In2Se3 nanoflakes. As characterized by piezoresponse force microscopy (PFM), when the in-plane (IP) electric polarization of 2H-stacked α-In2Se3 films is electrically aligned, the out-of-plane (OOP) polarization of the odd-layer (OL) samples is obviously larger than that of the even-layer (EL) ones. Similarly, samples with electrically aligned OOP polarization also show even–odd layer dependent IP polarization. Such an even–odd oscillation, as confirmed by the density functional theory calculations, can be attributed to the strong intercorrelation of the IP and OOP electric polarization of the α-In2Se3 monolayers and the special 2H-stacking structure of a 180 degree IP rotation with respect to the adjacent layers. Moreover, a negative differential resistance, interestingly, is induced by the polarization flip with a small coercive field of ∼1.625 kV cm−1, and its peak-to-valley ratio can be tuned up to ∼7 by the gate. This work demonstrates that the delicate stacking geometry of multilayer α-In2Se3 can bring an interesting even–odd ferroelectric effect, enriching the layer-dependent physical properties of the 2D materials family.
中文翻译：
2H 堆叠少层 α-In2Se3 中的层相关铁电性
原子级薄的二维（2D）范德华材料已经表现出许多奇异层依赖性物理性质，包括电子结构，磁顺序，等等在这里，我们报告一个引人注目的中强电介质极化偶数-奇数层依赖性振荡2H堆叠少层α-In 2 Se 3纳米薄片。正如压电响应力显微镜 (PFM) 所表征的那样，当 2H 堆叠的 α-In 2 Se 3的面内 (IP) 电极化薄膜是电对准的，奇数层 (OL) 样品的面外 (OOP) 偏振明显大于偶数层 (EL) 样品的面外 (OOP) 偏振。类似地，具有电对准 OOP 极化的样品也显示奇偶层相关的 IP 极化。这种奇偶振荡，正如密度泛函理论计算所证实的，可以归因于 α-In 2 Se 3单层的 IP 和 OOP 电极化的强相关性和180 度的特殊 2H 堆叠结构相对于相邻层的 IP 轮换。此外，有趣的是，负微分电阻是由具有 ~1.625 kV cm -1的小矫顽场的极化翻转引起的，并且它的峰谷比可以通过门调整到~7。这项工作表明，多层 α-In 2 Se 3的精细堆叠几何形状可以带来有趣的奇偶铁电效应，丰富了二维材料系列的层相关物理特性。
更新日期：2020-12-10
中文翻译：
2H 堆叠少层 α-In2Se3 中的层相关铁电性
原子级薄的二维（2D）范德华材料已经表现出许多奇异层依赖性物理性质，包括电子结构，磁顺序，等等在这里，我们报告一个引人注目的中强电介质极化偶数-奇数层依赖性振荡2H堆叠少层α-In 2 Se 3纳米薄片。正如压电响应力显微镜 (PFM) 所表征的那样，当 2H 堆叠的 α-In 2 Se 3的面内 (IP) 电极化薄膜是电对准的，奇数层 (OL) 样品的面外 (OOP) 偏振明显大于偶数层 (EL) 样品的面外 (OOP) 偏振。类似地，具有电对准 OOP 极化的样品也显示奇偶层相关的 IP 极化。这种奇偶振荡，正如密度泛函理论计算所证实的，可以归因于 α-In 2 Se 3单层的 IP 和 OOP 电极化的强相关性和180 度的特殊 2H 堆叠结构相对于相邻层的 IP 轮换。此外，有趣的是，负微分电阻是由具有 ~1.625 kV cm -1的小矫顽场的极化翻转引起的，并且它的峰谷比可以通过门调整到~7。这项工作表明，多层 α-In 2 Se 3的精细堆叠几何形状可以带来有趣的奇偶铁电效应，丰富了二维材料系列的层相关物理特性。
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