Efficient interfacial light-electric interconversion in van der Waals heterostructures is critical for their optoelectronic applications. Using time-resolved terahertz spectroscopy and transient absorption spectroscopy, the charge transfer and the dynamical interlayer excitons were investigated in the heterostructures comprising monolayer WSe2 and monolayer graphene with varying stacking order on a sapphire substrate. Herein, a more comprehensive understanding of ultrafast charge transfer and exciton dynamics in two-dimensional heterostructures is shown. Owing to the effective electric field induced by the sapphire substrate, the WSe2/graphene heterostructure exhibits positive terahertz photoconductivity after photoexcitation, while negative terahertz photoconductivity is observed in the graphene/WSe2 heterostructure. The transient absorption spectra indicate that the exciton lifetimes also exhibit a considerable difference, where WSe2/graphene exhibits the longest exciton lifetime, followed by monolayer WSe2, while graphene/WSe2 exhibits the shortest lifetime. These observations provide a new idea for using van der Waals heterostructures in electronic and photonic devices.

中文翻译：

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基质对单层WSe2 /石墨烯异质结构中超快界面电荷转移和动态层间激子的影响。

范德华异质结构中有效的界面光电互变对于其光电应用至关重要。使用时间分辨太赫兹光谱和瞬态吸收光谱，研究了在蓝宝石衬底上具有不同堆叠顺序的单层WSe2和单层石墨烯的异质结构中的电荷转移和动态层间激子。本文显示了对二维异质结构中超快电荷转移和激子动力学的更全面的了解。由于蓝宝石衬底感应的有效电场，WSe2 /石墨烯异质结构在光激发后呈现正太赫兹光电导性，而在石墨烯/ WSe2异质结构中观察到负太赫兹光电导性。瞬态吸收光谱表明，激子寿命也表现出相当大的差异，其中WSe2 /石墨烯表现出最长的激子寿命，其次是单层WSe2，而石墨烯/ WSe2表现出最短的寿命。这些发现为在电子和光子器件中使用范德华异质结构提供了新的思路。