Han Shuangping, Liang Xilong, Qin Chengbing, Gao Yan, Song Yunrui, Wang Shen, Su Xingliang, Zhang Guofeng, Chen Ruiyun, Hu Jianyong, Jing Mingyong, Xiao Liantuan, Jia Suotang
State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan, Shanxi 030006, China.
Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006, China.
ACS Nano. 2021 Aug 24;15(8):12966-12974. doi: 10.1021/acsnano.1c01787. Epub 2021 Jul 27.
van der Waals (vdW) heterostructures of transition metal dichalcogenides (TMDCs) provide an excellent paradigm for next-generation electronic and optoelectronic applications. However, the reproducible fabrications of vdW heterostructure devices and the boosting of practical applications are severely hindered by their unstable performance, due to the lack of criteria to assess the interlayer coupling in heterostructures. Here we propose a physical model involving ultrafast electron transfer in the heterostructures and provide two criteria, η (the ratio of the transferred electrons to the total excited electrons) and ζ (the relative photoluminescence variation), to evaluate the interlayer coupling by considering the electron transfer in TMDC heterostructures and numerically simulating the corresponding rate equations. We have proved the effectiveness and robustness of two criteria by measuring the pump-probe photoluminescence intensity of monolayer WS in the WS/WSe heterostructures. During thermal annealing of WS/WSe, ζ varies from negative to positive values and η changes between 0 and 4.5 × 10 as the coupling strength enhanced; both of them can well characterize the tuning of interlayer coupling. We also design a scheme to image the interlayer coupling by performing PL imaging at two time delays. Our scheme offers powerful criteria to assess the interlayer coupling in TMDC heterostructures, offering opportunities for the implementation of vdW heterostructures for broadband and high-performance electronic and optoelectronic applications.
过渡金属二硫属化物（TMDCs）的范德华（vdW）异质结构为下一代电子和光电子应用提供了一个出色的范例。然而，由于缺乏评估异质结构中层间耦合的标准，vdW异质结构器件的可重复制造以及实际应用的推进受到其不稳定性能的严重阻碍。在此，我们提出了一个涉及异质结构中超快电子转移的物理模型，并提供了两个标准，即η（转移电子与总激发电子的比率）和ζ（相对光致发光变化），通过考虑TMDC异质结构中的电子转移并对相应的速率方程进行数值模拟来评估层间耦合。我们通过测量WS/WSe异质结构中单层WS的泵浦 - 探测光致发光强度，证明了这两个标准的有效性和稳健性。在WS/WSe的热退火过程中，随着耦合强度的增强，ζ从负值变为正值，η在0到4.5×10之间变化；它们都能很好地表征层间耦合的调谐。我们还设计了一种通过在两个时间延迟下进行光致发光成像来对层间耦合进行成像的方案。我们的方案为评估TMDC异质结构中的层间耦合提供了有力的标准，为实现用于宽带和高性能电子及光电子应用的vdW异质结构提供了机会。
