MoS2 nanostructures: Semiconductors with metallic edges

We present theoretical calculations based on Density Functional Theory for MoS2 nanoribbons. By studying nanoribbons with various widths, the energy for the (10) edge in single-layer MoS2 is obtained. We calculate their electronic structure and use linear-response theory to obtain the dielectric function and other optoelectronic properties such as static relative permittivity, refractive index and reflectivity. We compare the dielectric properties of bulk (3D), single-layer (2D) and ribbons (quasi-1D) of MoS2 to find, among other trends, that the dielectric constant is almost halved when the dimensionality is reduced by one. The static relative permittivity drops from 7.1 in 3D to 3.7 in 2D, which is consistent with experimental data, and down to 2.4 in the quasi-1D case. We discuss the edge conducting states in ribbon MoS2, an otherwise semiconducting material, as well as its dielectric properties as a function of the ribbon width.