He Xing, Chebl Mazhar, Yang Ding-Shyue
Department of Chemistry, University of Houston, Houston, Texas 77204, United States.
Nano Lett. 2020 Mar 11;20(3):2026-2033. doi: 10.1021/acs.nanolett.9b05344. Epub 2020 Feb 25.
In this Letter, the ultrafast structural, interfacial, and carrier dynamics of monolayer MoS supported on sapphire are cross-examined by the combination of ultrafast electron diffraction (UED) and transient reflectivity techniques. The out-of-plane motions directly probed by reflection UED suggest a limited anisotropy in the atomic motions of monolayer MoS, which is distinct from that of related materials such as graphene and WSe. Besides thermal diffusion, the MoS-sapphire interface exhibits structural dynamics trailing those of the overlaying MoS and are in stark contrast with the sapphire bulk, which is consistent with the limited thermal boundary conductance. These structural dynamics provide justification for the determination of carriers being trapped by defects in ∼600 fs and releasing energy within a few picoseconds. The rich findings attest to the strength of combining techniques with real-time optical and direct structure probes for a detailed understanding of dynamical processes in functional materials.
在本信函中，通过超快电子衍射（UED）和瞬态反射率技术相结合的方法，对蓝宝石支撑的单层MoS₂的超快结构、界面和载流子动力学进行了交叉研究。反射UED直接探测到的面外运动表明，单层MoS₂的原子运动具有有限的各向异性，这与石墨烯和WSe₂等相关材料不同。除了热扩散外，MoS₂ - 蓝宝石界面表现出的结构动力学滞后于覆盖其上的MoS₂，这与蓝宝石块体形成鲜明对比，这与有限的热边界电导一致。这些结构动力学为确定载流子在约600飞秒内被缺陷捕获并在几皮秒内释放能量提供了依据。丰富的研究结果证明了将实时光学和直接结构探测技术相结合，对于详细了解功能材料中的动力学过程的优势。
