期刊
ADVANCED MATERIALS INTERFACES
卷 6, 期 23, 页码 -出版社
WILEY
DOI: 10.1002/admi.201901307
关键词
2D materials; excitons transport; photocarriers; transient absorption
资金
- National Key R&D Program of China [2016YFA0202302]
- National Natural Science Foundation of China [61527817, 61875236]
- Overseas Expertise Introduction Center for Discipline Innovation
- 111 Center of China
- National Science Foundation of USA [DMR-1505852]
An experimental study on the effect of hexagonal boron nitride (h-BN) underlay and cap layers on excitonic dynamics in monolayer WS2 is reported. A monolayer WS2 flake is fabricated by mechanical exfoliation. By using a dry transfer technique, three regions of the sample are obtained: WS2 directly on SiO2, WS2 on h-BN, and WS2 sandwiched by two h-BN flakes. Photoluminescence measurements show higher yield and narrower linewidth of the h-BN/WS2/h-BN region. Transient absorption measurements reveal that the top h-BN layer enhances the exciton formation, prolongs the exciton lifetime, and slightly affects the exciton-exciton annihilation. By performing spatially resolved transient absorption measurements, exciton diffusion coefficients of about 100, 40, and 26 cm(2) s(-)(1) for the regions of WS2, h-BN/WS2, and h-BN/WS2/h-BN, respectively, are obtained. The suppression of exciton diffusion by h-BN is attributed to the additional phonon scattering mechanisms introduced by h-BN, which decreases the exciton mean free path and thus the diffusion coefficient. The findings provide useful information for designing and understanding the effect of h-BN layers interfacing with 2D semiconductors.
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