Visualization of Dark Excitons in Semiconductor Monolayers for High-Sensitivity Strain Sensing
Visualization of Dark Excitons in Semiconductor Monolayers for High-Sensitivity Strain Sensing
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DOI：
10.1021/acs.nanolett.2c00436
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发表时间：
2022-04-13
期刊：
影响因子：
10.8
通讯作者：
Grosso, Gabriele
中科院分区：
文献类型：
--
作者：
Chand, Saroj B.;Woods, John M.;Grosso, Gabriele
过渡金属二硫属化物（TMD）是具有半导体相的层状材料，其具有许多有利的光电性质，包括紧密结合的激子和自旋谷锁定。在基于钨的TMD中，自旋和动量禁戒跃迁产生暗激子，暗激子通常是光学不可接近的，但代表系统的最低激子态。暗激子可以深刻地影响亮激子的传输、动力学和相干性，从而阻碍器件性能。因此，至关重要的是创造条件，使这些激子态可以可视化和控制。在这里，我们表明，WS2中的压缩应变使声子散射的光激发电子之间的动量谷，增强形成的黑暗谷间激子。我们发现，动量禁戒激子的发射和光谱特性是可访问的，并强烈依赖于修改能带排列的局部应变环境。这种机制被进一步开发用于二维半导体中的应变传感，揭示了超过104的应变计因子。
Transition-metal dichalcogenides (TMDs) are layered materials that have a semiconducting phase with many advantageous optoelectronic properties, including tightly bound excitons and spinvalley locking. In tungsten-based TMDs, spin- and momentumforbidden transitions give rise to dark excitons that typically are optically inaccessible but represent the lowest excitonic states of the system. Dark excitons can deeply affect the transport, dynamics, and coherence of bright excitons, hampering device performance. Therefore, it is crucial to create conditions in which these excitonic states can be visualized and controlled. Here, we show that compressive strain in WS2 enables phonon scattering of photoexcited electrons between momentum valleys, enhancing the formation of dark intervalley excitons. We show that the emission and spectral properties of momentum-forbidden excitons are accessible and strongly depend on the local strain environment that modifies the band alignment. This mechanism is further exploited for strain sensing in two-dimensional semiconductors, revealing a gauge factor exceeding 104.