Dependence of Electronic and Optical Properties of MoS Multilayers on the Interlayer Coupling and Van Hove Singularity.

In this paper, the structural, electronic, and optical properties of MoS multilayers are investigated by employing the first-principles method. Up to six-layers of MoS have been comparatively studied. The covalency and ionicity in the MoS monolayer are shown to be stronger than those in the bulk. As the layer number is increased to two or above two, band splitting is significant due to the interlayer coupling. We found that long plateaus emerged in the imaginary parts of the dielectric function [Formula: see text] and the joint density of states (JDOS) of MoS multilayers, due to the Van Hove singularities in a two-dimensional material. One, two and three small steps appear at the thresholds of both the long plateau of [Formula: see text] and JDOS, for monolayer, bilayer, and trilayer, respectively. As the number of layers further increased, the number of small steps increases and the width of the small steps decreases accordingly. Due to interlayer coupling, the longest plateau and shortest plateau of JDOS are from the monolayer and bulk, respectively.