Dilute Rhenium Doping and its Impact on Defects in MoS2

Abstract

Substitutionally doped 2D transition metal dichalcogenidesareprimed for next-generation device applications such as field effecttransistors (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-organicchemical vapor deposition (MOCVD). Surprisingly, we discover thateven trace amounts of Re lead to a reduction in sulfur site defectdensity by 5-10x. Ab initio models indicatethe origin of the reduction is an increase in the free-energy of sulfur-vacancyformation at the MoS2 growth-front when Re is introduced.Defect photoluminescence (PL) commonly seen in undoped MOCVD MoS2 is suppressed by 6x at 0.05 atomic percent (at. %) Reand completely quenched with 1 at. % Re. Furthermore, we find thatRe-MoS2 transistors exhibit a 2x increase in draincurrent and carrier mobility compared to undoped MoS2,indicating that sulfur vacancy reduction improves carrier transportin the Re-MoS2. This work provides important insights onhow dopants affect 2D semiconductor growth dynamics, which can leadto improved crystal quality and device performance.