Sebait Riya, Biswas Chandan, Song Bumsub, Seo Changwon, Lee Young Hee
ACS Nano. 2021 Feb 23;15(2):2849-2857. doi: 10.1021/acsnano.0c08828. Epub 2021 Jan 20.
Unusually high exciton binding energies (BEs), as much as ∼1 eV in monolayer transition-metal dichalcogenides, provide opportunities for exploring exotic and stable excitonic many-body effects. These include many-body neutral excitons, trions, biexcitons, and defect-induced excitons at room temperature, rarely realized in bulk materials. Nevertheless, the defect-induced trions correlated with charge screening have never been observed, and the corresponding BEs remain unknown. Here we report defect-induced A-trions and B-trions in monolayer tungsten disulfide (WS) carrier screening engineering with photogenerated carrier modulation, external doping, and substrate scattering. Defect-induced trions strongly couple with inherent SiO hole traps under high photocarrier densities and become more prominent in rhenium-doped WS. The absence of defect-induced trion peaks was confirmed using a trap-free hexagonal boron nitride substrate, regardless of power density. Moreover, many-body excitonic charge states and their BEs were compared carrier screening engineering at room temperature. The highest BE was observed in the defect-induced A-trion state (∼214 meV), comparably higher than the trion (209 meV) and neutral exciton (174 meV), and further tuned by external photoinduced carrier density control. This investigation allows us to demonstrate defect-induced trion BE localization spatial BE mapping in the monolayer WS midflake regions distinctive from the flake edges.
单层过渡金属二硫属化物中异常高的激子结合能（BEs），高达约1 eV，为探索奇异且稳定的激子多体效应提供了机会。这些效应包括多体中性激子、三重态激子、双激子以及室温下的缺陷诱导激子，而这些在体材料中很少能实现。然而，与电荷屏蔽相关的缺陷诱导三重态激子从未被观测到，其相应的结合能也仍然未知。在此，我们报告了在单层二硫化钨（WS）中通过光生载流子调制、外部掺杂和衬底散射进行载流子屏蔽工程所诱导的A三重态激子和B三重态激子。在高光载流子密度下，缺陷诱导的三重态激子与固有的SiO空穴陷阱强烈耦合，并且在掺铼的WS中更为显著。使用无陷阱的六方氮化硼衬底，无论功率密度如何，都证实了不存在缺陷诱导的三重态激子峰。此外，在室温下通过载流子屏蔽工程比较了多体激子电荷态及其结合能。在缺陷诱导的A三重态激子态中观察到了最高的结合能（约214 meV），相比三重态激子（209 meV）和中性激子（174 meV）要高得多，并且通过外部光诱导载流子密度控制可进一步调节。这项研究使我们能够在单层WS中与薄片边缘不同的中间薄片区域通过空间结合能映射来展示缺陷诱导的三重态激子结合能的定位。
