Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
Materials Engineering, McGill University, Montréal, Québec, H3A 0C5, Canada.
Sci Rep. 2017 Jan 13;7:40658. doi: 10.1038/srep40658.
One-dimensional semiconductor can undergo large deformation including stretching and bending. This homogeneous strain and strain gradient are an easy and effective way to tune the light emission properties and the performance of piezo-phototronic devices. Here, we report that with large strain gradients from 2.1-3.5% μm, free-exciton emission was intensified, and the free-exciton interaction (FXI) emission became a prominent FXI-band at the tensile side of the ZnO fiber. These led to an asymmetric variation in energy and intensity along the cross-section as well as a redshift of the total near-band-edge (NBE) emission. This evolution of the exciton emission was directly demonstrated using spatially resolved CL spectrometry combined with an in situ tensile-bending approach at liquid nitrogen temperature for individual fibers and nanowires. A distinctive mechanism of the evolution of exciton emission is proposed: the enhancement of the free-exciton-related emission is attributed to the aggregated free excitons and their interaction in the narrow bandgap in the presence of high bandgap gradients and a transverse piezoelectric field. These results might facilitate new approaches for energy conversion and sensing applications via strained nanowires and fibers.
一维半导体可以经历大变形，包括拉伸和弯曲。这种均匀应变和应变梯度是调节发光性质和压光电设备性能的一种简单而有效的方法。在这里，我们报告说，在 2.1-3.5%μm 的大应变梯度下，自由激子发射得到增强，自由激子相互作用（FXI）发射在 ZnO 纤维的拉伸侧成为一个突出的 FXI 带。这导致能量和强度沿着横截面的不对称变化以及总近带边（NBE）发射的红移。通过在液氮温度下使用空间分辨 CL 光谱结合原位拉伸弯曲方法对单个纤维和纳米线，直接证明了激子发射的这种演化。提出了激子发射演化的独特机制：在存在高能带梯度和横向压电场的情况下，窄带隙中聚集的自由激子及其相互作用导致了与自由激子相关的发射增强。这些结果可能通过应变纳米线和纤维促进能量转换和传感应用的新方法。
