Dilute Rhenium Doping and its Impact on Defects in MoS.

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 MoS 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×. models indicate the origin of the reduction is an increase in the free-energy of sulfur-vacancy formation at the MoS growth-front when Re is introduced. Defect photoluminescence (PL) commonly seen in undoped MOCVD MoS is suppressed by 6× at 0.05 atomic percent (at. %) Re and completely quenched with 1 at. % Re. Furthermore, we find that Re-MoS transistors exhibit a 2× increase in drain current and carrier mobility compared to undoped MoS, indicating that sulfur vacancy reduction improves carrier transport in the Re-MoS. This work provides important insights on how dopants affect 2D semiconductor growth dynamics, which can lead to improved crystal quality and device performance.