Can Stable MoS₂ Monolayers and Multilayers Be Constituted in the Biphenylene Network?

Abstract

Based on the first-principles calculations, we predict that the wellknown 2H-MoS 2 monolayer of the trigonal prismatic phase appearing in a hexagonal network can also constitute another stable phase in the biphenylene network (B-MoS 2 ). It consists of the connected octagon, hexagon and square rings and hence maintains the same numbers of neighbors of the constituent atoms, but its bonds between transition metal and chalcogen atoms are deformed to construct a direct but narrow band gap semiconductor with directional electronic conduction and optical properties with strong absorption in the near-infrared region. It has softer mechanical properties and site specific chemical activities of the same kind of constituent atoms. In the same way, vacancies of different chalcogen atoms in the cell attain different defect states in the band gap. This phase can remain stable above the room temperature and has a cohesive energy comparable to all the other 2D phases of the same compound. In fact, transitions from the 2H-phase to the Bphase can be possible. The B-phase can form multilayers and also a metallic 3D layered, van der Waals crystal with weak interlayer coupling. The narrow band gap of the monolayer is reduced in the bilayer but diminishes in multilayers and 3D layered crystals to change the semiconductor to a metal. Even more interesting is that B-MoS 2 is versatile for the modulation of the band gap, even for the metal−insulator transition under applied strains.