  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, we show
that the novel, ultrathin Ga$_2$O$_3$ glass is an ideal centimeter-scale
coating material that enhances optical performance of the monolayers and
protects them against further material deposition. In particular, Ga$_2$O$_3$
capping of commercial grade WS$_2$ monolayers outperforms hBN in both
scalability and optical performance at room temperature. These properties make
Ga$_2$O$_3$ highly suitable for large scale passivation and protection of
monolayer TMDCs in functional heterostructures.
