Controlling Exciton and Valley Dynamics in Two-Dimensional Heterostructures with Atomically Precise Interlayer Proximity
Controlling Exciton and Valley Dynamics in Two-Dimensional Heterostructures with Atomically Precise Interlayer Proximity
复制标题
利用原子级精确的层间邻近度控制二维异质结构中的激子和谷动力学
DOI：
10.1021/acsnano.0c00218
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发表时间：
2020
期刊：
影响因子：
17.1
通讯作者：
Zhu Haiming
中科院分区：
文献类型：
--
作者：
Zhou Hongzhi;Zhao Yida;Tao Weijian;Li Yujie;Zhou Qiaohui;Zhu Haiming
具有强激子效应和自旋/谷特性的二维（2D）材料和异质结构已经成为光电和自旋/谷电子应用的令人兴奋的平台。在那里，精确控制激子转换过程（包括层内到层间激子转换和复合）和谷极化过程通过结构调谐是至关重要的，但仍然在很大程度上未被探索。在这里，使用六方氮化硼（BN）作为中间层，我们显示了原子精度的二维异质结构中的激子和谷动力学的微调。随着BN厚度的增加，界面电子和空穴的传输速率均呈指数下降，这可以用量子隧穿模型来描述。BN的插入使得空间间距的增加削弱了电子-空穴的库仑相互作用，并显著提高了货车德瓦耳斯（vdW）异质结构的层间激子布居数和谷极化寿命。例如，在室温下，BN单层嵌入的WSe2/WS2异质结构的空穴谷极化寿命为1.60 ps，比未嵌入BN的WSe2/WS2异质双层结构和WSe2单层结构分别提高了3倍和3个数量级.考虑到一个大家庭的层状材料，这项研究提出了一种通用的方法来定制和优化激子和谷的性质，在VDW异质结原子精度。
Two-dimensional (2D) materials and heterostructures with strong excitonic effect and spin/valley properties have emerged as an exciting platform for optoelectronic and spin/valleytronic applications. There, precise control of the exciton transformation process (including intralayer to interlayer exciton transition and recombination) and valley polarization processviastructural tuning is crucial but remains largely unexplored. Here, using hexagonal boron nitride (BN) as an intermediate layer, we show the fine-tuning of exciton and valley dynamics in 2D heterostructures with atomic precision. Both interfacial electron and hole transfer rates decrease exponentially with increasing BN thickness, which can be well-described with quantum tunneling model. The increased spatial separation with BN intercalation weakens the electron–hole Coulomb interaction and significantly prolongs the interlayer exciton population and valley polarization lifetimes in van der Waals (vdW) heterostructures. For example, WSe2/WS2heterostructures with monolayer BN intercalation exhibit a hole valley polarization lifetime of ∼60 ps at room temperature, which is approximately threefold and 3 orders of magnitude longer than that in WSe2/WS2heterobilayer without BN and WSe2monolayer, respectively. Considering a large family of layered materials, this study suggests a general approach to tailor and optimize exciton and valley properties in vdW heterostructures with atomic precision.