Designing a Functionalized 2D-TMD (MoX₂, X = S, Se) Hosting Half-metallicity for Selective Gas-sensing Applications: Atomic-scale Study

The scope of the present investigation is to

design transition-metal “TM” doped transition-metal dichalcogenide “TMD”

monolayers (MoX₂, X = S, Se) that can host half-metallicity. The screening of various

TMs, using spin-polarized DFT calculations, yielded positive results on (Mn, Fe, and

Ni)-doped MoS₂ MLs and (V, Mn, Fe, and Co)-doped MoSe₂ to host half-metallicity

when smaller samples of sizes 4×4, 5×5, and 6×6 primitive cells (PCs) are considered.

The half-metallicity disappears for larger samples. The origin of this phenomenon can

be attributed to the existence of ferromagnetic-coupling (FMC) interactions, governing

the ground-state, involving the TM-dopant with its six mirror images, formed by the

periodic-boundary conditions. The disappearance of half metallicity is also associated

with a drastic change in magnetization. The critical length for the existence of

FMC is found to be dependent on both the host crystal and the type of magnetic

impurity; at the average is of the order of Lc ~ 20 Å. Furthermore, we investigated the

relevance of half-metallicity to gas-sensing applications. Our results showed the

half-metallicity is a useful property that can be explored for selective gas-sensing of

NO₂ gas molecules.