The effect of Mn-doping on structural, electronic, ferromagnetic, and optical properties of monolayer-WSe2 using first-principles calculations

Abstract

This study employs density functional theory, utilizing plane wave ultra-soft pseudopotentials (PW-USPPs) within the generalized gradient approximation (GGA) and incorporating the Hubbard potential (GGA + U), to investigate the structural, electronic, and magnetic characteristics of Mn-doped 2D—WSe₂ monolayers. The pristine WSe₂ monolayer is identified as a nonmagnetic direct band gap semiconductor with a band gap of 1.55 eV. Upon substituting Mn for W in the WSe₂ monolayer, the resulting structure exhibits enhanced stability, indicated by a negative formation energy. The Mn-doped monolayer-WSe₂ adopts a semi-metallic nature, deviating from the nonmagnetic characteristics of the pristine 2D—WSe₂, showcasing impurity bands dispersion near the Fermi level. The total magnetic moment within the nearest neighboring interactions of the Mn impurity atoms increases notably and it is attributed to the electron-correlation effect in the high spin state under the GGA + U approximation. However, this correlation effect proves insignificant on the total magnetic moment for the second nearest neighboring interactions, yielding consistent outcomes in both GGA and GGA + U approximations. The transition of ferromagnetic to antiferromagnetic states occurs within the temperature range of 400 K–450 K for low Mn-atom concentrations (below 12.5%), indicating long-range ferromagnetic ordering crucial for high-temperature 2D-diluted magnetic semiconductors. However, at high concentrations of impurity atoms, the temperature drops below room temperature (220 K in 22.2%) in the doped monolayer WSe₂, showing weak magnetic interaction. Lastly, the optical properties of the doped system is studied by applying polarization in perpendicular and parallel directions to the plane of the monolayer.

Graphical abstract