Fast Real-Space Imaging of the Exciton Complexes in WSe2 and WS2 Monolayers Using Multiphoton Microscopy

Kuang I. Lin, Shiue Yuan Shiau, Shu Bai Liu, Jia Sian Yan, Jia De Yan, Doreen Cheng, Han Ching Chang, Chien Liang Tu, Yung Chen Cheng, Chang Hsiao Chen

研究成果: Article同行評審

摘要

Two-dimensional transition metal dichalcogenides possess unprecedentedly strong optical nonlinear properties associated with exciton complexes, which are highly promising for developing novel optoelectronics and nanophotonics. In this work, we investigate various exciton complexes that exist in WSe2 and WS2 triangular monolayers, through second-harmonic generation (SHG) and two-photon excited photoluminescence (2P-PL) images that are generated rapidly by multiphoton laser scanning microscopy. These large-scale images taken at different photon energies reveal the spatial distribution of the exciton complexes. The SHG images capture the exciton and trion resonances but not the biexciton resonance, despite a prominent biexciton signature in 2P-PL. The peculiar absence of biexciton signature is explained using time-dependent perturbation theory. SHG can also resonate with the band nesting states to produce images with high contrast, which is out of reach in conventional PL. By analyzing the crystal structure and growth dynamics of WS2 monolayers using a high-angle annular dark-field scanning transmission electron microscope, we further establish the link between the oxidized triangular holes induced by S atom vacancies and the formation of biexcitons at the triangle edges. This newfangled approach using multiphoton microscopy shows that the spatial characteristics and excitation energy dependence of the exciton complexes are crucial for a deep understanding of the interactions between excitons and charged carriers and the two-dimensional materials in general.

原文English
頁(從 - 到)7979-7987
頁數9
期刊Journal of Physical Chemistry C
124
發行號14
DOIs
出版狀態Published - 2020 四月 9

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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