title: Strain-Gradient Modulated Exciton Emission in Bent ZnO Wires Probed by Cathodoluminescence.
abstract: 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-1, 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.
authors.forename: Xue-Wen
authors.initials: XW
authors.lastname: Fu
authors.forename: Cai-Zhen
authors.initials: CZ
authors.lastname: Li
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Fang
authors.affiliation: State Key Laboratory of Tribology, Tsinghua University , Beijing 100084, China.
authors.forename: Da-Meng
authors.initials: DM
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Physics, South University of Science and Technology of China , Shenzhen 518055, China.
authors.forename: Da-Peng
authors.initials: DP
authors.lastname: Yu
authors.affiliation: Collaborative Innovation Center of Quantum Matter , Beijing 100190, China.
authors.forename: Zhi-Min
authors.identifier: 0000-0001-6361-9626
authors.initials: ZM
authors.lastname: Liao
keywords: luminescence; semiconductor nanowires; strain; symmetry breaking