Investigating the dynamics of excitons in monolayer WSe2 before and after organic super acid treatment†,Nanoscale

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Investigating the dynamics of excitons in monolayer WSe2 before and after organic super acid treatment†
Nanoscale ( IF 5.8 ) Pub Date : 2018-04-16 00:00:00 , DOI: 10.1039/c8nr00774h
Xin Chen _{1,

2,

3,

4,

5} , Zhuo Wang _{5,

6,

7,

8,

9} , Lei Wang _{1,

2,

3,

4,

5} , Hai-Yu Wang _{1,

2,

3,

4,

5} , Yuan-Yuan Yue _{1,

2,

3,

4,

5} , Hai Wang _{1,

2,

3,

4,

5} , Xue-Peng Wang _{1,

2,

3,

4,

5} , Andrew T. S. Wee _{10,

11,

12,

13} , Cheng-Wei Qiu _{11,

13,

14,

15} , Hong-Bo Sun _{1,

2,

3,

4,

5}

Affiliation

State Key Laboratory of Integrated Optoelectronics
College of Electronic Science and Engineering
Jilin University
Changchun 130012
China
International Collaborative Lab of 2D Materials for Optoelectronics Science and Technology
College of Optoelectronic Engineering
Shenzhen University
Shenzhen 518060
Department of Physics
National University of Singapore
Singapore 117542
Singapore
Department of Electrical & Computer Engineering
Singapore 117583

Due to the large photoluminescence quantum yield, high mobility and good stability, organic super acid treated two-dimensional WSe₂ has drawn much attention. However, reports about the influence of organic super acid treatment on the dynamic processes of excitons of monolayer WSe₂ are still rare. In this work, through the broadband transient absorption spectra obtained using a femtosecond pump–probe system, we determine the dynamics of A′ and C excitons in monolayer and bulk WSe₂ at room temperature. Besides this, we also observe the relaxation process of the holes between the two spin split states in the valence band maximum in organic super acid treated monolayer WSe₂. We find that the organic super acid treatment on monolayer WSe₂ does not change the peak positions of the exciton states, while those bleaching peaks’ intensities increase significantly due to the enhancement of oscillator strength for exciton states, corresponding to stronger steady-state photoluminescence. This could be attributed to the strain release induced by the defect repairing effect during the organic super acid treatment process.

中文翻译：

研究有机超强酸处理前后单层WSe ₂中激子的动力学†

由于大的光致发光量子产率，高迁移率和良好的稳定性，有机过酸处理的二维WSe ₂引起了广泛的关注。然而，关于有机超强酸处理对单层WSe ₂激子动力学过程影响的报道仍然很少。在这项工作中，通过使用飞秒泵浦-探针系统获得的宽带瞬态吸收光谱，我们确定了室温下单层和整体WSe ₂中A'和C激子的动力学。除此之外，我们还观察到有机超酸处理的单层WSe ₂的价带最大时两个自旋分裂态之间的空穴的弛豫过程。我们发现单层WSe上的有机超强酸处理₂并没有改变激子态的峰值位置，而漂白峰的强度由于激子态的振子强度的增强而显着增加，这对应于更强的稳态光致发光。这可以归因于在有机超酸处理过程中由缺陷修复作用引起的应变释放。

更新日期：2018-04-16

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