Rare earth (Tm, Y, Gd, and Eu) doped ZnS monolayer: A comparative first-principles study.

In this current study, we used the density functional theory (DFT) method to examine the physical properties of ZnS nanosheets doped with Tm, Y, Gd, and Eu at a concentration of 6.25%. The non-magnetic phase is energetically stable when doped with Y and Tm. However, the ferromagnetic state is thermodynamically stable when doped with Eu and Gd with a negative formation energy value. The optimized structure is a planar structure for all doped systems, with an increase in the lattice parameter and bond length. On doping the Fermi level is pushed into the conduction band narrowing the band gap, and exhibiting typical n-type semiconducting behaviour. In a wider optical window, Tm and Y-doped systems have lower reflectance and more excellent transmittance than Gd and Eu-doped systems in the visible light spectrum. The electrical conductivity has been calculated using the BoltzTrap package. The electrical conductivity has been enhanced on doping suitable for its application in optoelectronic devices, solar cells, spintronics and thermoelectrics.