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

• Published in: ACS nano Vol. 8; no. 4; pp. 3412 - 3420
• Main Authors: Fu, Xuewen, Jacopin, Gwenole, Shahmohammadi, Mehran, Liu, Ren, Benameur, Malik, Ganière, Jean-Daniel, Feng, Ji, Guo, Wanlin, Liao, Zhi-Min, Deveaud, Benoit, Yu, Dapeng
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 22.04.2014
• Subjects: Cathodoluminescence; Drift; Dynamics; Excitation; Nanostructure; Semiconductors; Strain; Zinc oxide; strain gradient; pure bending strain; ZnO microwire; exciton dynamics; time-resolved cathodoluminescence
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/nn4062353

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.