Department of Chemistry, University of North Carolina at Chapel Hill , Chapel Hill, North Carolina 27599, United States.
Nano Lett. 2014 Nov 12;14(11):6287-92. doi: 10.1021/nl5026166. Epub 2014 Oct 3.
Strain-induced changes to the electronic structure of nanoscale materials provide a promising avenue for expanding the optoelectronic functionality of semiconductor nanostructures in device applications. Here we use pump-probe microscopy with femtosecond temporal resolution and submicron spatial resolution to characterize charge-carrier recombination and transport dynamics in silicon nanowires (NWs) locally strained by bending deformation. The electron-hole recombination rate increases with strain for values above a threshold of ∼1% and, in highly strained (∼5%) regions of the NW, increases 6-fold. The changes in recombination rate are independent of NW diameter and reversible upon reduction of the applied strain, indicating the effect originates from alterations to the NW bulk electronic structure rather than introduction of defects. The results highlight the strong relationship between strain, electronic structure, and charge-carrier dynamics in low-dimensional semiconductor systems, and we anticipate the results will assist the development of strain-enabled optoelectronic devices with indirect-bandgap materials such as silicon.
应变诱导的纳米材料电子结构变化为在器件应用中扩展半导体纳米结构的光电功能提供了有前途的途径。在这里，我们使用具有飞秒时间分辨率和亚微米空间分辨率的泵浦-探测显微镜来表征通过弯曲变形局部应变的硅纳米线（NW）中的载流子复合和输运动力学。对于大于约 1%的阈值的应变值，电子-空穴复合速率随应变增加，并且在 NW 的高度应变（约 5%）区域中增加 6 倍。复合速率的变化与 NW 直径无关，并且在施加应变降低时是可逆的，这表明该效应源自 NW 体电子结构的改变，而不是缺陷的引入。结果突出了低维半导体系统中应变、电子结构和载流子动力学之间的强关系，我们预计这些结果将有助于开发具有间接带隙材料（如硅）的应变致光电设备。
