Suppression of exciton-exciton annihilation in tungsten disulfide monolayers encapsulated by hexagonal boron nitrides
Suppression of exciton-exciton annihilation in tungsten disulfide monolayers encapsulated by hexagonal boron nitrides
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DOI：
10.1103/physrevb.95.241403
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发表时间：
2017-06-07
影响因子：
3.7
通讯作者：
Machida, Tomoki
中科院分区：
文献类型：
--
作者：
Hoshi, Yusuke;Kuroda, Takashi;Machida, Tomoki
我们研究了六方氮化硼 (hBN) 封装的二硫化钨 (WS2) 单层中的激子-激子湮灭 (EEA)。结果表明，时间分辨光致发光（PL）观察到的衰变信号并不强烈依赖于 hBN 封装的 WS2 单层（WS2/hBN）的激子密度。相比之下，没有底部 hBN 层 (WS2/SiO2) 的样品由于快速 PL 衰变成分的出现，随着激子密度的增加，衰变时间急剧减少，这表明非辐射 EEA 介导的复合。此外，WS2/hBN的EEA速率常数测定为(6.3+/-1.7)×10(-3)cm(2)s(-1)，比WS2/SiO2小约2个数量级。因此，观察到的 EEA 速率降低在增强 WS2 单层高激子密度下的发光强度方面发挥了关键作用。
We investigates exciton-exciton annihilation (EEA) in tungsten disulfide (WS2) monolayers encapsulated by hexagonal boron nitride (hBN). It is revealed that decay signals observed by time-resolved photoluminescence (PL) are not strongly dependent on the exciton densities of hBN-encapsulated WS2 monolayers (WS2/hBN). In contrast, the sample without the bottom hBN layer (WS2/SiO2) exhibits a drastic decrease of decay time with increasing exciton density due to the appearance of a rapid PL decay component, signifying nonradiative EEA-mediated recombination. Furthermore, the EEA rate constant of WS2/hBN was determined as (6.3 +/- 1.7) x 10(-3) cm(2) s(-1), being about 2 orders of magnitude smaller than that of WS2/SiO2. Thus, the observed EEA rate reduction played a key role in enhancing luminescence intensity at high exciton densities in the WS2 monolayer.