Multidirection Piezoelectricity in Mono- and Multilayered Hexagonal α-In2Se3
Multidirection Piezoelectricity in Mono- and Multilayered Hexagonal α-In2Se3
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DOI：
10.1021/acsnano.8b02152
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发表时间：
2018-05-01
期刊：
影响因子：
17.1
通讯作者：
Li, Lain-Jong
中科院分区：
文献类型：
--
作者：
Xue, Fei;Zhang, Junwei;Li, Lain-Jong
压电材料已被广泛应用于传感器、执行器、电子学和能量转换等领域。二维超薄半导体，如单层h-BN和MoS_2，由于其原子级的几何结构，目前正在成为压电家族中新的和有吸引力的成员。然而，它们的压电极化通常局限在奇数超薄层的面内方向，这在很大程度上限制了它们在集成纳米机电系统中的应用。最近，理论计算预测了单层α-In2Se_3中存在面外和面内压电性。在此，我们实验地报道了体相α-In2Se_3的面外和面内压电性共存的现象，这归因于它们起源于六方堆积的非中心对称性。具体来说，α-In2Se_3的d(33)压电系数从0.34 pm/V(单层)增加到5.6 pm/V(体相)，没有奇偶效应。此外，我们还展示了一种基于α-In2Se_3的柔性压电纳米发电机作为能量收集细胞和电子皮肤。α-In2Se3薄片的面外和面内压电性为定向和非定向压电器件提供了机会，使其能够应用于自供电系统和自适应和应变可调电子/光电子学。
Piezoelectric materials have been widely used for sensors, actuators, electronics, and energy conversion. Two-dimensional (2D) ultrathin semiconductors, such as monolayer h-BN and MoS2 with their atom-level geometry, are currently emerging as new and attractive members of the piezoelectric family. However, their piezoelectric polarization is commonly limited to the in-plane direction of odd-number ultrathin layers, largely restricting their application in integrated nanoelectromechanical systems. Recently, theoretical calculations have predicted the existence of out-of-plane and in-plane piezoelectricity in monolayer alpha-In2Se3. Here, we experimentally report the coexistence of out-of-plane and in-plane piezoelectricity in monolayer to bulk alpha-In2Se3, attributed to their noncentrosymmetry originating from the hexagonal stacking. Specifically, the corresponding d(33) piezoelectric coefficient of alpha-In2Se3 increases from 0.34 pm/V (monolayer) to 5.6 pm/V (bulk) without any odd even effect. In addition, we also demonstrate a type of alpha-In2Se3-based flexible piezoelectric nanogenerator as an energy-harvesting cell and electronic skin. The out-of-plane and in-plane piezoelectricity in alpha-In2Se3 flakes offers an opportunity to enable both directional and nondirectional piezoelectric devices to be applicable for self-powered systems and adaptive and strain tunable electronics/optoelectronics.