Simultaneous generation of direct- and indirect-gap photoluminescence in multilayer MoS2 bubbles
Simultaneous generation of direct- and indirect-gap photoluminescence in multilayer MoS2 bubbles
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多层 MoS2 气泡中同时产生直接和间接间隙光致发光
DOI：
10.1103/physrevmaterials.4.074006
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发表时间：
2020-07-20
影响因子：
3.4
通讯作者：
Zhou, Xingjiang
中科院分区：
文献类型：
--
作者：
Luo, Hailan;Li, Xuanyi;Zhou, Xingjiang
过渡金属二硫属化物（TMD）材料由于其非凡的光学和电学性能而受到极大的关注，其中MoS2是最具代表性的例子之一。随着厚度从单层到多层的增加，由于直接到间接的带隙转变，MoS2的光致发光（PL）逐渐淬灭。如何提高多层MoS2的PL响应并降低其层间依赖性仍然是一个挑战。在这项工作中，我们报告同时产生三个PL峰在1.3，1.4和1.8 eV左右的多层二硫化钼气泡。温度相关的PL测量表明，在1.3和1.4 eV的两个峰来自声子辅助的间接带隙跃迁，而在1.8 eV的峰来自直接带隙跃迁。低频拉曼光谱证实了多层膜MoS2气泡层间耦合的减弱，这可能是导致PL峰出现的原因。采用第一性原理计算方法，研究了多层膜MoS2在应变作用下的能带结构演化，进一步证实了MoS2泡的三个PL峰的来源。此外，PL驻波中观察到MoS2气泡，创建牛顿环样图案。这项工作表明，气泡结构可能为工程层状材料的电子结构和光学性质提供新的机会。
Transition metal dichalcogenide (TMD) materials have received enormous attention due to their extraordinary optical and electrical properties, with MoS2 being one of the most representative examples. As the thickness increases from monolayer to multilayer, the photoluminescence (PL) of MoS2 is gradually quenched due to the direct-to-indirect band gap transition. How to enhance PL response and decrease the layer dependence in multilayer MoS2 remains a challenge. In this work, we report simultaneous generation of three PL peaks at around 1.3, 1.4, and 1.8 eV on multilayer MoS2 bubbles. The temperature dependent PL measurements indicate that the two peaks at 1.3 and 1.4 eV come from phonon-assisted indirect-gap transitions while the peak at 1.8 eV comes from the direct-gap transition. The weakening of interlayer coupling on multilayer MoS2 bubbles, which may account for the emergence of PL peaks, is confirmed by the low-frequency Raman spectroscopy. Using first-principles calculations, the band structure evolution of multilayer MoS2 under strain is studied, from which the origin of the three PL peaks of MoS2 bubbles is further confirmed. Moreover, PL standing waves are observed in MoS2 bubbles that create Newton-Ring-like patterns. This work demonstrates that the bubble structure may provide new opportunities for engineering the electronic structure and optical properties of layered materials.