title: Strain Gradient Modulated Exciton Evolution and Emission in ZnO Fibers.
abstract: 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-1, 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.
authors.affiliation: 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.
authors.forename: Bin
authors.initials: B
authors.lastname: Wei
authors.affiliation: Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Ji
authors.affiliation: Materials Engineering, McGill University, Montréal, Québec, H3A 0C5, Canada.
authors.forename: Raynald
authors.initials: R
authors.lastname: Gauvin
authors.affiliation: Department of Materials Science, Zhejiang University, Hangzhou 310027, China.
authors.forename: Ze
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Materials Engineering and Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia, QLD 4072, Australia.
authors.forename: Jin
authors.initials: J
authors.lastname: Zou
authors.affiliation: Beijing Key Laboratory and Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124, China.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Han