Sulphur isotope engineering in MoS2 monolayers. Midjourney, CC BY-NC.
MoS2 is one of the most extensively studied materials among two-dimensional transition metal di-chalcogenides. Although one study shows enhanced thermal conductivity in MoS2 monolayer via Mo isotope engineering, the optoelectronic properties are yet to be addressed.
Sulfur occurs in 23 different known isotopes with atomic masses ranging from 27 to 49. The most stable and most abundant isotopes are 32S and 34S. In our work, we focused on the monolayers composed of natural sulphur, isotopically pure 32S and 34S, and a 1:1 ratio of 32S and 34S. We carried out an extensive investigation of the lattice dynamics, reformed due to the isotopic abundance. We have also carried out a thorough investigation of exciton formation and dynamics using temperature and time dependent photoluminescence measurements in the isotope-modified monolayers. We have demonstrated that phonon scattering, exciton formation, and their life times can be efficiently tuned via sulphur isotope engineering.
