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arXiv 1902.00461cond-mat.mes-hall
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vdW异质结构层间激子动量守恒超快电荷转移动力学

Momentum Conserved Ultrafast Charge Transfer Dynamics of Interlayer Excitons in vdW Heterostructures

Pranjal Kumar Gogoi, Yung-Chang Lin, Ryosuke Senga, Hannu-Pekka Komsa, Swee Liang Wong, Dongzhi Chi, Arkady V. Krasheninnikov, Lain-Jong Li, Mark B. H. Breese, … 展开作者

Pranjal Kumar Gogoi, Yung-Chang Lin, Ryosuke Senga, Hannu-Pekka Komsa, Swee Liang Wong, Dongzhi Chi, Arkady V. Krasheninnikov, Lain-Jong Li, Mark B. H. Breese, Steven J. Pennycook, Andrew T. S. Wee, Kazu Suenaga

摘要:

由范德华(vdW)堆叠的过渡金属二硫属化物(TMDC)单层构成的异质结构是一类具有独特性质的迷人的二维(2D)材料。层间激子的存在,其中电子和空穴由于超快电荷转移而在两层中保持空间分离,是这些异质结构的一个有趣的特征。不可避免地,2D异质结构器件的效率关键取决于电荷转移动力学。然而,该电荷转移动力学的组成层的相对旋转角度的作用是迄今为止未知的。在这里,我们调查的MoS $_2$ /WSe $_2$ VDW异质结(HMW)使用单色低损耗电子能量损失(EEL)光谱结合像差校正扫描透射电子显微镜(STEM),并报告说,动量守恒是一个关键因素的电荷转移动力学的TMDC VDW异质结。具有不同旋转角度的异质结构的低损耗EEL谱显示,在对准(或反对准)的情况下,电荷转移速率可以比未对准的情况快大约一个数量级。这些结果提供了一个更深入的了解动量守恒的基本原理在二维vdW异质结电荷转移动力学的作用。

英文摘要:

Heterostructures comprising van der Waals (vdW) stacked transition metal dichalcogenide (TMDC) monolayers are a fascinating class of two-dimensional (2D) materials with unique properties. The presence of interlayer excitons, where the electron and the hole remain spatially separated in the two layers due to ultrafast charge transfer, is an intriguing feature of these heterostructures. Inevitably, the efficiency of 2D heterostructure devices is critically dependent on the charge transfer dynamics. However, the role of the relative rotation angle of the constituent layers on this charge transfer dynamics is hitherto unknown. Here, we investigate MoS$_2$/WSe$_2$ vdW heterostructures (hMWs) using monochromated low-loss electron energy loss (EEL) spectroscopy combined with aberration-corrected scanning transmission electron microscopy (STEM), and report that momentum conservation is a critical factor in the charge transfer dynamics of TMDC vdW heterostructures. The low-loss EEL spectra of the heterostructures with various rotation angles reveal that the charge transfer rate can be about one order-of-magnitude faster in the aligned (or anti-aligned) case than the misaligned cases. These results provide a deeper insight into the role of the fundamental principle of momentum conservation in 2D vdW heterostructure charge transfer dynamics.

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