title: Spatiotemporal dynamics of excitons in monolayer and bulk WS2.
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.
authors.affiliation: Key Laboratory of Luminescence and Optical Information, Ministry of Education, Institute of Optoelectronic Technology, Beijing Jiaotong University, Beijing 100044, China. dwhe@bjtu.edu.cn yshwang@bjtu.edu.cn.
authors.forename: Jiaqi
authors.initials: J
authors.lastname: He
authors.forename: Dawei
authors.initials: D
authors.lastname: He
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Wang
authors.forename: Qiannan
authors.initials: Q
authors.lastname: Cui
authors.forename: Frank
authors.initials: F
authors.lastname: Ceballos
authors.forename: Hui
authors.initials: H
authors.lastname: Zhao