Manganese Doping of Monolayer MoS ₂: The Substrate Is Critical

Substitutional doping of transition metal dichalcogenides (TMDs) may provide routes to achieving tunable p-n junctions, bandgaps, chemical sensitivity, and magnetism in these materials. In this study, we demonstrate in situ doping of monolayer molybdenum disulfide (MoS ₂ ) with manganese (Mn) via vapor phase deposition techniques. Successful incorporation of Mn in MoS ₂ leads to modifications of the band structure as evidenced by photoluminescence and X-ray photoelectron spectroscopy, but this is heavily dependent on the choice of substrate. We show that inert substrates (i.e., graphene) permit the incorporation of several percent Mn in MoS ₂ , while substrates with reactive surface terminations (i.e., SiO ₂ and sapphire) preclude Mn incorporation and merely lead to defective MoS ₂ . The results presented here demonstrate that tailoring the substrate surface could be the most significant factor in substitutional doping of TMDs with non-TMD elements.