Ultrathin Ga₂ O₃ Glass: A Large-Scale Passivation and Protection Material for Monolayer WS₂

Atomically thin transition metal dichalcogenide crystals (TMDCs) have extraordinary optical properties that make them attractive for future optoelectronic applications. Integration of TMDCs into practical all-dielectric heterostructures hinges on the ability to passivate and protect them against necessary fabrication steps on large scales. Despite its limited scalability, encapsulation of TMDCs in hexagonal boron nitride (hBN) currently has no viable alternative for achieving high performance of the final device. Here, it is shown that the novel, ultrathin Ga₂ O₃ glass is an ideal centimeter-scale coating material that enhances optical performance of the monolayers and protects them against further material deposition. In particular, Ga₂ O₃ capping of monolayer WS₂ outperforms commercial-grade hBN in both scalability and optical performance at room temperature. These properties make Ga₂ O₃ highly suitable for large-scale passivation and protection of monolayer TMDCs in functional heterostructures.