State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China.
Department of Physics, South University of Science and Technology of China , Shenzhen 518055, China.
ACS Nano. 2016 Dec 27;10(12):11469-11474. doi: 10.1021/acsnano.6b07206. Epub 2016 Dec 1.
Photoelectrical properties of semiconductor nanostructures are expected to be improved significantly by strain engineering. Besides the local strain, the strain gradient is promising to tune the luminescence properties by modifying the crystal symmetry. Here, we report the investigation of strain-gradient induced symmetry-breaking effect on excitonic states in pure bending ZnO microwires by high spatial-resolved cathodoluminescence at low temperature of 80 K. In addition to the local-strain induced light emission peak shift, the bound exciton emission photon energy shows an extraordinary jump of ∼16.6 meV at a high strain-gradient of 1.22% μm, which is ascribed to the strain gradient induced symmetry-breaking. Such a symmetry-breaking lifts the energy degeneracy of the electronic band structures, which significantly modifies the electron-hole interactions and the fine structures of the bound exciton states. These results provide a further understanding of the strain gradient effect on the excitonic states and possess a potential for the applications in optoelectronic devices.
通过应变工程，半导体纳米结构的光电性能有望得到显著改善。除了局部应变之外，应变梯度有望通过改变晶体对称性来调整发光性能。在这里，我们通过在 80 K 的低温下进行高空间分辨的低温阴极发光研究，报告了纯弯曲 ZnO 微丝中应变梯度对激子态的对称性破缺效应的研究。除了由局部应变引起的光发射峰位移外，在应变梯度为 1.22%μm 的情况下，束缚激子发射光子能量显示出异常的 16.6 meV 跃变，这归因于应变梯度诱导的对称性破缺。这种对称性破缺消除了电子能带结构的能量简并，从而显著改变了电子-空穴相互作用和束缚激子态的精细结构。这些结果提供了对应变梯度对激子态影响的进一步理解，并在光电设备的应用中具有潜力。
