A first principle Comparative study of electronic and optical properties of 1H – MoS2 and 2H – MoS2

First principle calculations of electronic and optical properties of monolayer MoS2, so called 1H – MoS2, is performed which has emerged as a new direct band gap semiconductor. Before calculations of the properties of 1H – MoS2, we have calculated structural parameters, electronic properties (electronic band structure and electronic density of states) and frequency dependent optical response (real and imaginary part of dielectric function, energy loss function, absorption and reflectance spectra) of 2H – MoS2 and compared with existing experimental results and found that our calculated results are in very good agreements with experimental results. To compare the dielectric functions of bulk (2H – MoS2) and monolayer (1H – MoS2) phases we have further extended these calculations to the single layer MoS2 (1H – MoS2) which is analogous to graphene. Structural parameters of 1H – MoS2 are found very close to its bulk 2H – MoS2. We find direct electronic band gap at ‘K’ high symmetry point as compared to indirect band gap in its bulk 2H – MoS2. Our calculated dielectric function for 1H – MoS2 shows structure at nearly same energy positions as compared to 2H – MoS2 with additional structure at 3.8 eV. Also additional well defined energy loss peaks revealing the plasmonic resonances at 15.7 eV and 16.0 eV for E vector perpendicular and parallel to c axis respectively for 1H – MoS2 have been found, which are the signatures of surface plasmons at these energies.

► Structural parameters of 2H-MoS2 and 1H-MoS2 are nearly identical.
► States around the Fermi energy are mainly due to the metal d states.
► Strong hybridization between Mo-d and S-p states below the Fermi energy has been found.
► Optical spectra of 2H-MoS2 finds very good agreements with experimental optical spectra.
► The band gap is found to be direct for 1H-MoS2 as compared to indirect for 2H-MoS2.