Dilute Rhenium Doping and its Impact on Defects in MoS₂

Substitutionally doped 2D transition metal dichalcogenides are primed for next-generation device applications such as field effect transistors (FET), sensors, and optoelectronic circuits. In this work, we demonstrate substitutional rhenium (Re) doping of MoS₂ monolayers with controllable concentrations down to 500 ppm by metal-organic chemical vapor deposition (MOCVD). Surprisingly, we discover that even trace amounts of Re lead to a reduction in sulfur site defect density by 5-10×. Ab initio models indicate the origin of the reduction is an increase in the free-energy of sulfur-vacancy formation at the MoS₂ growth-front when Re is introduced. Defect photoluminescence (PL) commonly seen in undoped MOCVD MoS₂ is suppressed by 6× at 0.05 atomic percent (at. %) Re and completely quenched with 1 at. % Re. Furthermore, we find that Re-MoS₂ transistors exhibit a 2× increase in drain current and carrier mobility compared to undoped MoS₂, indicating that sulfur vacancy reduction improves carrier transport in the Re-MoS₂. This work provides important insights on how dopants affect 2D semiconductor growth dynamics, which can lead to improved crystal quality and device performance.