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Title: Twisted MoSe 2 bilayers with variable local stacking and interlayer coupling revealed by low-frequency Raman spectroscopy

Unique twisted bilayers of MoSe 2 with multiple stacking orientations and interlayer couplings in the narrow range of twist angles, 60 ± 3°, are revealed by low-frequency Raman spectroscopy and theoretical analysis. The slight deviation from 60 allows the concomitant presence of patches featuring all three high-symmetry stacking configurations (2H or AA', AB', A'B) in one unique bilayer system. In this case, the periodic arrangement of the patches and their size strongly depend on the twist angle. Ab initio modeling predicts significant changes in frequencies and intensities of low-frequency modes versus stacking and twist angle. Experimentally, the variable stacking and coupling across the interface is revealed by the appearance of two breathing modes corresponding to the mixture of the high-symmetry stacking configurations and unaligned regions of monolayers. Only one breathing mode is observed outside the narrow range of twist angles. This indicates a stacking transition to unaligned monolayers with mismatched atom registry without the in-plane restoring force required to generate a shear mode. As a result, the variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide a new platform for optoelectronic applications of these materials.
 [1] ;  [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Rensselaer Polytechnic Institute (RPI), Troy, NY (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 10; Journal Issue: 2; Journal ID: ISSN 1936-0851
American Chemical Society
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
77 NANOSCIENCE AND NANOTECHNOLOGY; two-dimensional materials; transition metal dichalcogenides; low-frequency Raman spectroscopy; stacking configurations; first-principles calculations
OSTI Identifier: