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Excitonic Transport and Intervalley Scattering Dynamics in Large‐Size Exfoliated MoSe2 Monolayer Investigated by Heterodyned Transient Grating Spectroscopy
Laser & Photonics Reviews ( IF 9.8 ) Pub Date : 2020-11-16 , DOI: 10.1002/lpor.202000029 Henning Kuhn 1 , Julian Wagner 1 , Shuangping Han 2 , Robin Bernhardt 1 , Yan Gao 3 , Liantuan Xiao 2 , Jingyi Zhu 1 , Paul H. M. Loosdrecht 1
Laser & Photonics Reviews ( IF 9.8 ) Pub Date : 2020-11-16 , DOI: 10.1002/lpor.202000029 Henning Kuhn 1 , Julian Wagner 1 , Shuangping Han 2 , Robin Bernhardt 1 , Yan Gao 3 , Liantuan Xiao 2 , Jingyi Zhu 1 , Paul H. M. Loosdrecht 1
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Exciton intervalley scattering, annihilation, relaxation dynamics, and diffusive transport in monolayer transition metal dichalcogenides are central to the functionality of devices based on them. Here, these properties in a large‐size exfoliated high‐quality monolayer MoSe2 are addressed directly using heterodyned transient grating spectroscopy at room temperature. While the free exciton population is found to be long‐lived (≈230 ps), an extremely fast intervalley scattering (≤170 fs) is observed, leading to a negligible valley polarization, consistent with steady state photoluminescence measurements and theoretical calculation. The exciton population decay shows an appreciable contribution from the exciton–exciton annihilation, with an annihilation rate of ≈0.01 cm2 s−1. The annihilation process also leads to a significant distortion of the transient grating evolution. Taking this distortion into account, consistent exciton diffusion constants D ≈ 1.4 cm2 s−1 are found by a model simulation in the excitation density range of 1011–1012 cm−2. The presented results highlight the importance of correctly considering the many‐body annihilation processes to obtain a pronounced understanding of the excitonic properties of monolayer transition metal dichalcogenides.
中文翻译：
异质瞬态光栅光谱研究大尺寸剥落的MoSe2单层中的激子输运和区间散射动力学。
单层过渡金属二卤化物中的激子区间散射、,灭，弛豫动力学和扩散传输是基于它们的器件功能的关键。在这里，在室温下使用杂化瞬态光栅光谱法可以直接解决大型剥落的高质量单层MoSe 2中的这些特性。尽管发现自由激子寿命长（≈230ps），但观察到极快的间隔散射（≤170fs），导致谷偏振可忽略不计，这与稳态光致发光测量和理论计算一致。激子种群衰减显示出激子-激子an灭的显着贡献，an灭速率约为0.01 cm 2 s -1。ni灭过程还导致瞬态光栅演变的严重失真。采取这一失真考虑在内，一致的激子扩散常数ð ≈1.4厘米2个 小号-1通过在10激发密度范围内的模型的仿真中发现11 -10 12 厘米-2。提出的结果突出了正确考虑多体an灭过程以获得对单层过渡金属二卤化金属的激子性质的深刻理解的重要性。
更新日期：2020-12-12
中文翻译：
异质瞬态光栅光谱研究大尺寸剥落的MoSe2单层中的激子输运和区间散射动力学。
单层过渡金属二卤化物中的激子区间散射、,灭，弛豫动力学和扩散传输是基于它们的器件功能的关键。在这里，在室温下使用杂化瞬态光栅光谱法可以直接解决大型剥落的高质量单层MoSe 2中的这些特性。尽管发现自由激子寿命长（≈230ps），但观察到极快的间隔散射（≤170fs），导致谷偏振可忽略不计，这与稳态光致发光测量和理论计算一致。激子种群衰减显示出激子-激子an灭的显着贡献，an灭速率约为0.01 cm 2 s -1。ni灭过程还导致瞬态光栅演变的严重失真。采取这一失真考虑在内，一致的激子扩散常数ð ≈1.4厘米2个 小号-1通过在10激发密度范围内的模型的仿真中发现11 -10 12 厘米-2。提出的结果突出了正确考虑多体an灭过程以获得对单层过渡金属二卤化金属的激子性质的深刻理解的重要性。
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