Valley Polarization in Superacid-Treated Monolayer MoS2,ACS Applied Electronic Materials

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Valley Polarization in Superacid-Treated Monolayer MoS2
ACS Applied Electronic Materials ( IF 4.3 ) Pub Date : 2020-06-09 , DOI: 10.1021/acsaelm.0c00277
Ruijie Li _{1,

2,

3,

4} , Yifei Li ₁ , Huifeng Tian ₁ , PeiChi Liao ₁ , Hanyu Wang ₅ , Shengnan Zhang _{1,

6} , Zhixin Yao _{1,

6} , Haicheng Wang _{2,

3} , Shizhuo Liu ₁ , Guanwei Chen ₁ , Shulei Yu ₁ , Zhenjiang Li ₁ , Junjiang Liu ₇ , Zhi Xu ₇ , Fuhong Mei ₆ , Peizhi Liu ₆ , Junjie Guo ₆ , Kaihui Liu ₈ , Xiao Li ₅ , Lei Liu ₁

Affiliation

The interplay between excitons and point defects in semiconductors plays a critical role in optical and optoelectronic properties, especially within a reduced dimensional system. Recently, it has been shown that the superacid treatment on a monolayer sulfur-based transition metal dichalcogenide (TMDC) provided efficient defect repairing/passivation, leading to an enhanced photoluminescence (PL) quantum yield and exciton radiative lifetime by more than two orders of magnitude. Meanwhile, the TMDC monolayer possesses valley-contrast properties and consequently valleytronics applications in which one key parameter, valley polarization, is in principle inversely proportional to the exciton lifetime, suggesting the degraded valley polarization after the superacid treatment. The behavior of the valley properties in the superacid-treated sulfur-based TMDC monolayer remains largely unexplored. Here, we perform detailed steady-state circularly polarized PL characterizations on superacid-treated MoS₂ monolayers. We show the ultrahigh stability of the acid molecule’s decoration in the high vacuum and low temperature environments. While one counterintuitive finding is the presence of defect-bound emissions at low temperature after the treatment, the temperature-dependent behavior of the valley polarization does not show any significant variation before and after the treatment. An exciton-decaying model involved with deep trapped states is utilized, accompanied by the theoretically re-built valley polarization expression, to comprehend experimental findings. Our results suggest that the superacid-treated sulfur-based TMDCs with superior PL performance and unaffected valley properties are an excellent candidate for applications of highly efficient valleytronic devices.

中文翻译：

酸处理过的单分子膜MoS _2中的波谷极化

半导体中激子和点缺陷之间的相互作用在光学和光电特性中，尤其是在尺寸减小的系统中，起着至关重要的作用。最近，研究表明，对单层硫基过渡金属二硫化碳（TMDC）进行超酸处理可提供有效的缺陷修复/钝化，从而将光致发光（PL）量子产率和激子辐射寿命提高了两个数量级以上。。同时，TMDC单层具有波谷对比度特性，因此在波谷电子学应用中，一个关键参数，波谷极化，原则上与激子寿命成反比，表明在超酸处理后，波谷极化性能降低。在超酸处理的硫基TMDC单层中，谷性质的行为仍未得到充分探索。在这里，我们对超酸处理的MoS进行详细的稳态圆极化PL表征_2个单层。我们展示了在高真空和低温环境下酸分子装饰物的超高稳定性。尽管有一个反常理的发现是在处理后的低温下存在缺陷束缚发射，但谷值极化的温度相关行为在处理前后并没有显示任何明显变化。利用与深陷陷态有关的激子衰减模型，并伴随理论上重建的谷极化表达，来理解实验结果。我们的结果表明，具有优异的PL性能和不受影响的波谷特性的超酸处理硫基TMDC是高效谷波电子器件应用的绝佳候选者。

更新日期：2020-07-28

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