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Title: Structural Phase Transformation in Strained Monolayer MoWSe 2 Alloy

Two-dimensional (2D) materials exhibit different mechanical properties from their bulk counterparts owing to their monolayer atomic thickness. In this paper, we have examined the mechanical behavior of 2D molybdenum tungsten diselenide (MoWSe 2) precipitation alloy grown using chemical vapor deposition and composed of numerous nanoscopic MoSe 2 and WSe 2 regions. Applying a bending strain blue-shifted the MoSe 2 and WSe 2 A 1g Raman modes with the stress concentrated near the precipitate interfaces predominantly affecting the WSe 2 modes. In situ local Raman measurements suggested that the crack propagated primarily thorough MoSe 2-rich regions in the monolayer alloy. Molecular dynamics (MD) simulations were performed to study crack propagation in an MoSe 2 monolayer containing nanoscopic WSe 2 regions akin to the experiment. Raman spectra calculated from MD trajectories of crack propagation confirmed the emergence of intermediate peaks in the strained monolayer alloy, mirroring experimental results. The simulations revealed that the stress buildup around the crack tip caused an irreversible structural transformation from the 2H to 1T phase both in the MoSe 2 matrix and WSe 2 patches. This was corroborated by high-angle annular dark-field images. Finally, crack branching and subsequent healing of a crack branch were also observed inmore » WSe 2, indicating the increased toughness and crack propagation resistance of the alloyed 2D MoWSe 2 over the unalloyed counterparts.« less
Authors:
 [1] ; ORCiD logo [1] ;  [2] ; ORCiD logo [2] ; ORCiD logo [3] ;  [4] ;  [4] ;  [3] ; ORCiD logo [2] ; ORCiD logo [2] ;  [2] ; ORCiD logo [5] ;  [1]
  1. Rice Univ., Houston, TX (United States). Dept. of Materials Science and Nano Engineering
  2. Univ. of Southern California, Los Angeles, CA (United States). Collaboratory for Advanced Computing and Simulations. Dept. of Physics and Astronomy. Dept. of Computer Science. Dept. of Chemical Engineering and Materials Science. Dept. of Biological Sciences
  3. Bruker Nano Surfaces, Eden Prairie, MN (United States)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science
  5. Rice Univ., Houston, TX (United States). Dept. of Materials Science and Nano Engineering; Indian Inst. of Technology (IIT), Gandhinagar (India). Materials Science and Engineering
Publication Date:
Grant/Contract Number:
AC05-00OR22725; SC0014607
Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 12; Journal Issue: 4; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Southern California, Los Angeles, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; mechanical straining; molecular dynamics simulations; Raman spectroscopy; transition-metal dichalcogenide; two-dimensional materials
OSTI Identifier:
1460185