Strain-mediated stability and electronic properties of WS2, Janus WSSe and WSe2 monolayers

Authors

Rajneesh Chaurasiya, Indian Institute of Technology Jodhpur
Ambesh Dixit, Indian Institute of Technology Jodhpur
Ravindra Pandey, Michigan Technological UniversityFollow

Document Type

Article

Publication Date

10-2018

Department

Department of Physics

Abstract

Monolayers of transition metal dichalcogenides (TMDs) have been proposed as the next generation electronic materials for nanoscale devices. We evaluated the thermodynamic stability of WS₂, Janus WSSe and WSe₂ monolayers under biaxial tensile and compressive strain using density functional approach. The phonon band structures of unstrained WS₂, WSSe and WSe₂ monolayers confirm their thermodynamic stability. The stability of these monolayers is investigated under strain and phonon softening is observed for acoustic and optical mode up to 8% tensile strain. The bond length reduction under compressive strain resulted in out of plane deformation, leading the instability of monolayers under compressive strain. The bond length W-S(Se) and bond angle W-S(Se)-W exhibit significant contribution in coupling strength between transition metal d-orbitals and chalcogen p-orbitals that mediated the electronic properties. The spin orbit coupling showed strong effect on splitting of the valence band for unstrained monolayers. The spin splitting in valence band increases with increasing the tensile strain and decreases with increasing the compressive strain. The effective masses and mobility values are 0.57m_e, 0.54m_e, 0.47m_e; and 0.059, 0.062, 0.072 m²V⁻¹s⁻¹ for unstrained WS₂, WSSe and WSe₂ monolayers, respectively. The tungsten d_x2-y2 orbitals are mainly contributing to the conduction and valence band electronic states in compressive strained monolayers. In contrast under tensile strain tungsten d_z2 orbitals contribute to conduction and valence band electronic states, causing the direct to indirect band gap transition in these monolayers. We observed that the impact of tensile strain is more sensitive as compared to that of compressive strain.

Publisher's Statement

© 2018 Elsevier Ltd. All rights reserved. Publisher’s version of record: https://doi.org/10.1016/j.spmi.2018.07.039

Publication Title

Supperlattices and Microstructures

Recommended Citation

Chaurasiya, R., Dixit, A., & Pandey, R. (2018). Strain-mediated stability and electronic properties of WS2, Janus WSSe and WSe2 monolayers. Supperlattices and Microstructures, 122, 268-279. http://doi.org/10.1016/j.spmi.2018.07.039
Retrieved from: https://digitalcommons.mtu.edu/michigantech-p/414