Isotope-Engineering the Thermal Conductivity of Two-Dimensional MoS₂

Isotopes represent a degree of freedom that might be exploited to tune the physical properties of materials while preserving their chemical behaviors. Here, we demonstrate that the thermal properties of two-dimensional (2D) transition-metal dichalcogenides can be tailored through isotope engineering. Monolayer crystals of MoS₂ were synthesized with isotopically pure ¹⁰⁰Mo and ⁹²Mo by chemical vapor deposition employing isotopically enriched molybdenum oxide precursors. The in-plane thermal conductivity of the ¹⁰⁰MoS₂ monolayers, measured using a non-destructive, optothermal Raman technique, is found to be enhanced by ∼50% compared with the MoS₂ synthesized using mixed Mo isotopes from naturally occurring molybdenum oxide. The boost of thermal conductivity in isotopically pure MoS₂ monolayers is attributed to the combined effects of reduced isotopic disorder and a reduction in defect-related scattering, consistent with observed stronger photoluminescence and longer exciton lifetime. These results shed light on the fundamentals of 2D nanoscale thermal transport important for the optimization of 2D electronic devices.