FU Xuewen, GUO Wanlin and YU Dapeng, et al. Exciton Drift in Semiconductors under Uniform Strain Gradients: Application to Bent ZnO Microwires. ACS Nano 2014, 8, 3412–3420.

Exciton Drift in Semiconductors under Uniform Strain Gradients: Application to Bent ZnO Microwires

Xuewen Fu †, Gwenole Jacopin ‡, Mehran Shahmohammadi ‡, Ren Liu †, Malik Benameur §, Jean-Daniel Ganière ‡, Ji Feng , Wanlin Guo , Zhi-Min Liao †, Benoit Deveaud ‡*, and Dapeng Yu †*
† State Key Laboratory for Mesoscopic Physics, and Electron Microscopy Laboratory, Department of Physics, Peking University, 209 Chengfu Road, Beijing 100871, China
‡ Laboratoire d’Optoélectronique Quantique, École Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland
§ Attolight AG, EPFL Innovation Square, PSE D, 1015 Lausanne, Switzerland
International Center for Quantum Materials, School of Physics, Peking University, Beijing 100871, China
State Key Laboratory of Mechanics and Control of Mechanical Structures and Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, China

ACS Nano, 2014, 8 (4), pp 3412–3420
DOI: 10.1021/nn4062353
Publication Date (Web): March 21, 2014
Copyright © 2014 American Chemical Society
*Address correspondence to benoit.deveaud-pledran@epfl.ch; yudp@pku.edu.cn.

Abstract
Optimizing the electronic structures and carrier dynamics in semiconductors at atomic scale is an essential issue for innovative device applications. Besides the traditional chemical doping and the use of homo/heterostructures, elastic strain has been proposed as a promising possibility. Here, we report on the direct observation of the dynamics of exciton transport in a ZnO microwire under pure elastic bending deformation, by using cathodoluminescence with high temporal, spatial, and energy resolutions. We demonstrate that excitons can be effectively drifted by the strain gradient in inhomogeneous strain fields. Our observations are well reproduced by a drift-diffusion model taking into account the strain gradient and allow us to deduce an exciton mobility of 1400 ± 100 cm2/(eV s) in the ZnO wire. These results propose a way to tune the exciton dynamics in semiconductors and imply the possible role of strain gradient in optoelectronic and sensing nano/microdevices.

Keywords: ZnO microwire; time-resolved cathodoluminescence; pure bending strain; exciton dynamics; strain gradient

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