Utilizing complex oxide substrates to control carrier concentration in large-area monolayer MoS₂ films

Bandgap engineering is central to the design of heterojunction devices. For heterojunctions involving monolayer-thick materials like MoS₂, the carrier concentration of the atomically thin film can vary significantly depending on the amount of charge transfer between MoS₂ and the substrate. This makes substrates with a range of charge neutrality levels—as is the case for complex oxide substrates—a powerful addition to electrostatic gating or chemical doping to control the doping of overlying MoS₂ layers. We demonstrate this approach by growing monolayer MoS₂ on perovskite (SrTiO₃ and LaAlO₃), spinel (MgAl₂O₄), and SiO₂ substrates with multi-inch uniformity. The as-grown MoS₂ films on these substrates exhibit a controlled, reproducible, and uniform carrier concentration ranging from (1–4) ×10¹³ cm⁻², depending on the oxide substrate employed. The observed carrier concentrations are further confirmed by our density-functional theory calculations based on ab initio mismatched interface theory (MINT). This approach is relevant to large-scale heterostructures involving monolayer-thick materials in which it is desired to precisely control carrier concentrations for applications.