Abstract
We report a theoretical investigation, based on density functional theory calculations, of the role of chalcogen species and the number of monolayers in the physical-chemical properties of multilayer two-dimensional transition-metal dichalcogenides (TMDs, MQ(2)), where M belongs to groups 8 and 10 of the periodic table, Q = S, Se, or Te, and the multilayer is composed of 1 to 6 layers. From the analysis of structural energetic, and electronic properties, we found significant changes in lattice parameters and exfoliation energies as a function of the number of layers, particularly affected by the chalcogen Q species. The TMDs in group 8 exhibit similar lattice parameters for the same choice of chalcogens, making them suitable for constructing commensurate heterostructures, while the crystal phase and the lattice parameter of the TMDs in group 10 strongly depend on the choice of the transition-metal species. Furthermore, the decreasing trend of electronegativity from S to Te results in stronger exfoliation energies due to lower surface charges, thus governing the structural and electronic characteristics of few-layer TMDs. We find unexpected electronic characteristics, such as band gap increases driven by spin-orbit coupling for certain compositions, the emergence of polarization electric fields due to point inversion symmetry breaking, and semiconductor-to-metal transitions with minimal layer additions to the monolayer. The presence of sulfur improves the sensitivity of the surface properties, enabling precise tuning of band edge positions with the layer number.