DIAEE-Electrical Engineering Division, 'Sapienza' University of Rome, Via Eudossiana 18, 00184, Rome, Italy.
Nanotechnology. 2013 Jul 5;24(26):265707. doi: 10.1088/0957-4484/24/26/265707. Epub 2013 Jun 4.
Quasi-1D piezoelectric nanostructures may offer unprecedented sensitivity for transducing minuscule input mechanical forces into high output voltages due to both scaling laws and increased piezoelectric coefficients. However, until now both theoretical and experimental studies have suggested that, for a given mechanical force, lateral bending of piezoelectric nanowires results in lower output electric potentials than vertical compression. Here we demonstrate that this result only applies to nanostructures with a constant cross-section. Moreover, though it is commonly believed that the output electric potential of a strained piezo-semiconductive device can only be reduced by the presence of free charges, we show that the output piezopotential of laterally bent tapered nanostructures, with typical doping levels and very small input forces, can be even increased up to two times by free charges.Our analyses confirm that, though not optimal for piezoelectric energy harvesting, lateral bending of tapered nanostructures with typical doping levels can be ideal for transducing tiny input mechanical forces into high and accessible piezopotentials. Our results provide guidelines for designing high-performance piezo-nano-devices for energy harvesting, mechanical sensing, piezotronics, piezo-phototronics, and piezo-controlled chemical reactions, among others.
准一维压电纳米结构由于尺寸缩减规律和压电系数增加，有望将微小的输入机械力转换为高输出电压，从而提供前所未有的灵敏度。然而，到目前为止，理论和实验研究都表明，对于给定的机械力，压电纳米线的横向弯曲会导致输出电势比垂直压缩低。在这里，我们证明了这一结果仅适用于具有恒定横截面的纳米结构。此外，尽管人们普遍认为应变的压电器件的输出电势只能通过自由电荷的存在来降低，但我们表明，对于具有典型掺杂水平和非常小输入力的横向弯曲锥形纳米结构，输出压电势甚至可以通过自由电荷增加高达两倍。我们的分析证实，尽管对于压电能量收集来说不是最佳的，但具有典型掺杂水平的锥形纳米结构的横向弯曲对于将微小的输入机械力转换为高且可访问的压电势非常理想。我们的研究结果为设计用于能量收集、机械传感、压电器件、光电压电器件和压控化学反应等的高性能压电机纳米器件提供了指导。
