Twisted MoSe2 Bilayers with Variable Local Stacking and Interlayer Coupling Revealed by Low-Frequency Raman Spectroscopy

Alexander A. Puretzky; Liangbo Liang; Xufan Li; Kai Xiao; Bobby G. Sumpter; Vincent Meunier; David B. Geohegan

doi:10.1021/acsnano.5b07807

Twisted MoSe₂ Bilayers with Variable Local Stacking and Interlayer Coupling Revealed by Low-Frequency Raman Spectroscopy

Alexander A. Puretzky, Liangbo Liang, Xufan Li, Kai Xiao, Bobby G. Sumpter, Vincent Meunier, David B. Geohegan

Research output: Contribution to journal › Article › peer-review

131 Scopus citations

Abstract

Unique twisted bilayers of MoSe₂ 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′, and 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 are 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. The variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide an interesting platform for optoelectronic applications of these materials.

Original language	English
Pages (from-to)	2736-2744
Number of pages	9
Journal	ACS Nano
Volume	10
Issue number	2
DOIs	https://doi.org/10.1021/acsnano.5b07807
State	Published - Feb 23 2016

Funding

The Raman spectroscopy part of this research, including aspects of theory, was conducted at the Center for Nanophase Materials Sciences, a U.S. Department of Energy Office of Science User Facility. The synthesis science including CVD was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. The theoretical work at Rensselaer Polytechnic Institute (RPI) was supported by NSF EFRI-2DARE 1542707. L.L. was supported by a Eugene P. Wigner Fellowship at the Oak Ridge National Laboratory. The computations were performed using the resources of the Center for Computational Innovation at RPI. This manuscript has been authored by UTBattelle, LLC, under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Funders	Funder number
DOE Public Access Plan
United States Government
National Science Foundation	EFRI-2DARE 1542707
U.S. Department of Energy
Office of Science
Basic Energy Sciences
Oak Ridge National Laboratory	DE-AC05-00OR22725
Division of Materials Sciences and Engineering

Keywords

first-principles calculations
low-frequency Raman spectroscopy
stacking configurations
transition metal dichalcogenides
two-dimensional materials

Access to Document

10.1021/acsnano.5b07807

Cite this

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title = "Twisted MoSe2 Bilayers with Variable Local Stacking and Interlayer Coupling Revealed by Low-Frequency Raman Spectroscopy",

abstract = "Unique twisted bilayers of MoSe2 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′, and 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 are 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. The variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide an interesting platform for optoelectronic applications of these materials.",

keywords = "first-principles calculations, low-frequency Raman spectroscopy, stacking configurations, transition metal dichalcogenides, two-dimensional materials",

author = "Puretzky, {Alexander A.} and Liangbo Liang and Xufan Li and Kai Xiao and Sumpter, {Bobby G.} and Vincent Meunier and Geohegan, {David B.}",

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AU - Xiao, Kai

AU - Sumpter, Bobby G.

AU - Meunier, Vincent

AU - Geohegan, David B.

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N2 - Unique twisted bilayers of MoSe2 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′, and 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 are 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. The variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide an interesting platform for optoelectronic applications of these materials.

AB - Unique twisted bilayers of MoSe2 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′, and 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 are 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. The variable interlayer coupling and spacing in transition metal dichalcogenide bilayers revealed in this study may provide an interesting platform for optoelectronic applications of these materials.

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