Influence of Rhenium Concentration on Charge Doping and Defect Formation in MoS₂

Substitutionally doped transition metal dichalcogenides (TMDs) are essential for advancing TMD-based field effect transistors, sensors, and quantum photonic devices. However, the impact of local dopant concentrations and dopant–dopant interactions on charge doping and defect formation within TMDs remains underexplored. Here, a breakthrough understanding of the influence of rhenium (Re) concentration is presented on charge doping and defect formation in MoS₂ monolayers grown by metal–organic chemical vapor deposition (MOCVD). It is shown that Re-MoS₂ films exhibit reduced sulfur-site defects, consistent with prior reports. However, as the Re concentration approaches ⪆2 atom%, significant clustering of Re in the MoS₂ is observed. Ab Initio calculations indicate that the transition from isolated Re atoms to Re clusters increases the ionization energy of Re dopants, thereby reducing Re-doping efficacy. Using photoluminescence (PL) spectroscopy, it is shown that Re dopant clustering creates defect states that trap photogenerated excitons within the MoS₂ lattice, resulting in broad sub-gap emission. These results provide critical insights into how the local concentration of metal dopants influences carrier density, defect formation, and exciton recombination in TMDs, offering a novel framework for designing future TMD-based devices with improved electronic and photonic properties.