Department of Mechanical Engineering, Northwestern University, Evanston, Illinois 60208-3111, USA.
Nano Lett. 2011 Feb 9;11(2):786-90. doi: 10.1021/nl104004d. Epub 2011 Jan 11.
Nanowires made of materials with noncentrosymmetric crystal structure are under investigation for their piezoelectric properties and suitability as building blocks for next-generation self-powered nanodevices. In this work, we investigate the size dependence of piezoelectric coefficients in nanowires of two such materials - zinc oxide and gallium nitride. Nanowires, oriented along their polar axis, ranging from 0.6 to 2.4 nm in diameter were modeled quantum mechanically. A giant piezoelectric size effect is identified for both GaN and ZnO nanowires. However, GaN exhibits a larger and more extended size dependence than ZnO. The observed size effect is discussed in the context of charge redistribution near the free surfaces leading to changes in local polarization. The study reveals that local changes in polarization and reduction of unit cell volume with respect to bulk values lead to the observed size effect. These results have strong implication in the field of energy harvesting, as piezoelectric voltage output scales with the piezoelectric coefficient.
具有非中心对称晶体结构的材料制成的纳米线因其压电性能以及作为下一代自供电纳米器件构建块的适用性而受到研究。在这项工作中，我们研究了两种材料 - 氧化锌和氮化镓 - 的纳米线中压电系数的尺寸依赖性。纳米线沿其极轴取向，直径从 0.6 到 2.4nm 不等，通过量子力学进行建模。发现对于 GaN 和 ZnO 纳米线都存在巨大的压电尺寸效应。然而，GaN 比 ZnO 表现出更大和更扩展的尺寸依赖性。在导致局部极化变化的自由表面附近的电荷再分配的背景下讨论了观察到的尺寸效应。研究表明，局部极化变化和相对于体值的单位细胞体积的减少导致了观察到的尺寸效应。这些结果在能量收集领域具有重要意义，因为压电电压输出与压电系数成正比。
