Distinctive optoelectronic properties of nanostructured MoS2 bilayers

Abstract

We theoretically investigate the electronic and optical properties of nanostructured ${\mathrm{MoS}}_{2}$ bilayers, consisting of vertically stacked monolayer (ML) of pristine ${\mathrm{MoS}}_{2}$ and ML of periodic triangular nanoplatelets or holes. Our calculations reveal that the interplay between edge atoms in periodic nanostructures, size of nanostructures, and distances between them, control the appearance and size of the band gaps, and optical response, including the number and intensity of peaks; the nanostructured bilayers with periodic nanoplatelets in particular exhibit rich optical properties. Specifically, we find the electronic states, originating from the atoms of the ML with either periodic nanoplatelets or holes, get embedded between electronic states of pristine ${\mathrm{MoS}}_{2}$ ML, but now with red- and blueshifted valence and conduction bands, respectively. For a ML with periodic nanoplatelets, electronic states originate primarily from $p$ orbitals of S atoms, and for a ML with periodic holes, they originate from $d$ orbitals of Mo atoms. The electronic structure is accessed through the self-consistent tight-binding (SCTB) method, which is the extension of our tested parametrized TB model that includes nonorthogonal ${sp}^{3}{d}^{5}$ orbitals and spin-orbit coupling. We systematically examine the parameters in our SCTB to avoid possible distortion of electronic states, ensuring high quality of our predictions.