单层和块状二硫化钨中激子的时空动力学

Spatiotemporal dynamics of excitons in monolayer and bulk WS2.

作者信息

He Jiaqi, He Dawei, Wang Yongsheng, Cui Qiannan, Ceballos Frank, Zhao Hui

机构信息

Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China.

出版信息

Nanoscale. 2015 Jun 7;7(21):9526-31. doi: 10.1039/c5nr00188a.

DOI:10.1039/c5nr00188a

PMID:25947347

Abstract

Spatiotemporal dynamics of excitons in monolayer and bulk WS2 at room temperature is studied by transient absorption microscopy in the reflection geometry. Excitons are formed from photocarriers injected by a tightly focused 390 nm pump pulse, and monitored by detecting different reflection of a time-delayed and spatially scanned 620 nm probe pulse. We obtain exciton lifetimes of 22 ± 1 and 110 ± 10 ps in monolayer and bulk WS2, respectively. Both lifetimes are independent of the exciton density, showing the absence of multi-exciton recombination processes. Exciton diffusion coefficients of 60 ± 20 and 3.5 ± 0.5 cm(2) s(-1) are obtained in monolayer and bulk samples, respectively. These results provide a foundation for understanding excitons in this new material and its optoelectronic applications.

摘要

通过反射几何结构中的瞬态吸收显微镜研究了室温下单层和体相WS2中激子的时空动力学。激子由紧聚焦的390 nm泵浦脉冲注入的光载流子形成，并通过检测延迟和空间扫描的620 nm探测脉冲的不同反射来监测。我们分别在单层和体相WS2中获得了22±1和110±10 ps的激子寿命。这两个寿命均与激子密度无关，表明不存在多激子复合过程。在单层和体相样品中分别获得了60±20和3.5±0.5 cm² s⁻¹的激子扩散系数。这些结果为理解这种新材料中的激子及其光电应用奠定了基础。