课题组硕士生曹凌恺在国际物理光学期刊Optics Express上发表论文

2020-07-01 09:36:04 677

 近日，课题组成员曹凌恺同学在刘老师的指导下，以第一作者在美国光学学会旗下著名光学期刊Optics Express上发表题为“Valley-polarized local excitons in WSe2/WS2 vertical heterostructures(二维材料WSe2/WS2垂直异质结构中局域激子谷极化特性的研究)”的实验论文。

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图一：二维材料WSe2/WS2垂直异质结的制备

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图二：二维材料WSe2/WS2垂直异质结构中局域激子谷极化特性

  二维材料范德华异质结构(vdWHs)因为其独特的光电性能，为现代新型信息器件的开发提供了更多的选择。到目前为止，在vdWH的基础上已发展出几种功能器件，例如：场效应晶体管，高灵敏度化学传感器和高性能光电探测器。值得注意的是，范德华层间相互作用为vdWH提供了比单层2D材料更多的新颖特性。这些新特性之一便是type II型异质结的中性激子光致发光(PL)猝灭现象，导致了局部激子的荧光PL增强的情况。但目前大多数报道的vdWHs是通过机械剥离法制备的，从而限制了它们的大规模生产和实际应用。此外，WSe2/WS2异质结构中局部激子的圆极化特性仍然难以被观察到。针对上述挑战问题，我们实验室采用双向流物理气相沉积技术。在实验中使用反向气流冷却以减少WSe2/WS2异质结构生长过程中的不良成核现象，并成功合成type II型WSe2/WS2垂直异质结构。这种异质结的界面清晰而干净，使垂直异质结构的中性激子淬灭，从而显着突出了局部激子的PL发光。此外，我们成功地证明了WSe2/WS2异质结构中局部激子的圆极化特性的存在，其中σ- 检测的极化度为7.17％，σ+检测的极化度为4.78％。这种局部激子在实现增加自发发射速率的量子发射器中起关键作用，推动了其在量子点LED的发展。我们的观察结果为研究激子物理学和开拓局域激子在新型量子点发光领域的应用提供了实验支撑和理论支持。

论文链接：https://opg.optica.org/oe/fulltext.cfm?uri=oe-28-15-22135&id=433379&ibsearch=false

Comments:

  • Valley-polarized local excitons in WSe2/WS2 vertical heterostructures are a novel type of excitons that are formed by the interaction of electrons and holes in a two-dimensional material. These excitons are unique because they are polarized, meaning that they have a specific direction of oscillation, which is determined by the crystal structure of the material. In WSe2/WS2 vertical heterostructures, the polarization direction is determined by the valley index of the material, which is related to the direction of the energy band minimum in the material.

  • Valley-polarized excitons have been found to exhibit unique optical properties, including valley-selective optical absorption and emission. This makes them attractive for use in optoelectronic devices, such as valley-based transistors and valleytronics, which have the potential to revolutionize the field of electronics.

  • In WSe2/WS2 vertical heterostructures, the valley polarization of the excitons is enhanced due to the stacking of different two-dimensional materials. This allows for efficient valley-based charge and energy transfer, leading to increased device performance.

  • Overall, the study of valley-polarized local excitons in WSe2/WS2 vertical heterostructures is an exciting area of research, with potential applications in the fields of electronics and optoelectronics.