Layer Rotation-Angle-Dependent Excitonic Absorption in van der Waals Heterostructures Revealed by Electron Energy Loss Spectroscopy

Research output: Contribution to journalArticleScientificpeer-review


Research units

  • National Institute of Advanced Industrial Science and Technology
  • Agency for Science, Technology and Research
  • Helmholtz-Zentrum Dresden-Rossendorf
  • King Abdullah University of Science and Technology
  • National University of Singapore


Heterostructures comprising van der Waals (vdW) stacked transition metal dichalcogenide (TMDC) monolayers are a fascinating class of two-dimensional (2D) materials. The presence of interlayer excitons, where the electron and the hole remain spatially separated in the two layers due to ultrafast charge transfer, is an intriguing feature of these heterostructures. The optoelectronic functionality of 2D heterostructure devices is critically dependent on the relative rotation angle of the layers. However, the role of the relative rotation angle of the constituent layers on intralayer absorption is not clear yet. Here, we investigate MoS2/WSe2 vdW heterostructures using monochromated low-loss electron energy loss (EEL) spectroscopy combined with aberration-corrected scanning transmission electron microscopy and report that momentum conservation is a critical factor in the intralayer absorption of TMDC vdW heterostructures. The evolution of the intralayer excitonic low-loss EEL spectroscopy peak broadenings as a function of the rotation angle reveals that the interlayer charge transfer rate can be about an order of magnitude faster in the aligned (or anti-aligned) case than in the misaligned cases. These results provide a deeper insight into the role of momentum conservation, one of the fundamental principles governing charge transfer dynamics in 2D vdW heterostructures.


Original languageEnglish
Pages (from-to)9541-9550
JournalACS Nano
Issue number8
Early online date25 Jul 2019
Publication statusPublished - 27 Aug 2019
MoE publication typeA1 Journal article-refereed

    Research areas

  • electron energy loss spectroscopy, interlayer excitons, scanning transmission electron microscopy, ultrafast charge transfer, van der Waals heterostructure

ID: 36261908