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Stress-driven structural and bond reconstruction in 2D ferromagnetic semiconductor VSe 2 .

Bo-Wen YuBang-Gui Liu
Published in: Nanotechnology (2022)
Two-dimensional (2D) semiconducting transition metal dichalcogenides can be used to make high-performance electronic, spintronic, and optoelectronic devices. Recently, room-temperature ferromagnetism and semiconduction in 2D VSe 2 nanoflakes were attributed to the stable 2H-phase of VSe 2 in the 2D limit. Here, our first-principles investigation shows that a metastable semiconducting H' phase can be formed from the H VSe2 monolayer through uniaxial stress or uniaxial strain. The calculated phonon spectra indicate the dynamical stability of the metastable H' VSe 2 and the path of phase switching between the H and H' VSe 2 phases is calculated. For the uniaxial stress (or strain) scheme, the H' phase can become lower in total energy than the H phase at a transition point. The H' phase has stronger ferromagnetism and its Curier temperature can be enhanced by applying uniaxial stress or strain. Applying uniaxial stress or strain can substantially change spin-resolved electronic structures, energy band edges, and effective carrier masses for both of the H and H' phases, and can cause some flat bands near the band edges in the strained H' phase. Further analysis indicates that one of the Se-Se bonds in the H' phase can be shortened by 19% and the related Se-V-Se bond angles are reduced by 23% with respect to those of the H phase, which is believed to increase the Se-Se covalence feature and reduce the valence of the nearby V atoms. Therefore, structural and bond reconstruction can be realized by applying uniaxial stress in such 2D ferromagnetic semiconductors for potential spintronic and optoelectronic applications.
Keyphrases
  • room temperature
  • transition metal
  • ionic liquid
  • stress induced
  • high resolution
  • machine learning
  • computed tomography
  • density functional theory
  • mass spectrometry
  • heat stress
  • molecular dynamics