Yagodkin Denis, Kumar Abhijeet, Ankerhold Elias, Richter Johanna, Watanabe Kenji, Taniguchi Takashi, Gahl Cornelius, Bolotin Kirill I
Department of Physics, Freie Universität Berlin, Arnimallee 14, Berlin 14195, Germany.
Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
Nano Lett. 2023 Oct 25;23(20):9212-9218. doi: 10.1021/acs.nanolett.3c01708. Epub 2023 Oct 3.
Optically dark excitons determine a wide range of properties of photoexcited semiconductors yet are hard to access via conventional time-resolved spectroscopies. Here, we develop a time-resolved ultrafast photocurrent technique (trPC) to probe the formation dynamics of optically dark excitons. The nonlinear nature of the trPC makes it particularly sensitive to the formation of excitons occurring at the femtosecond time scale after the excitation. As a proof of principle, we extract the interlayer exciton formation time of 0.4 ps at 160 μJ/cm fluence in a MoS/MoSe heterostructure and show that this time decreases with fluence. In addition, our approach provides access to the dynamics of carriers and their interlayer transport. Overall, our work establishes trPC as a technique to study dark excitons in various systems that are hard to probe by other approaches.
光学暗激子决定了光激发半导体的多种性质，但通过传统的时间分辨光谱学很难对其进行研究。在此，我们开发了一种时间分辨超快光电流技术（trPC）来探测光学暗激子的形成动力学。trPC的非线性特性使其对激发后飞秒时间尺度上激子的形成特别敏感。作为原理验证，我们在MoS/MoSe异质结构中，在160 μJ/cm的能量密度下提取了层间激子的形成时间为0.4皮秒，并表明该时间随能量密度的增加而减小。此外，我们的方法还能研究载流子的动力学及其层间输运。总的来说，我们的工作确立了trPC作为一种研究各种难以用其他方法探测的系统中暗激子的技术。
