<Abstrate>

Despite the direct band gap of monolayer transition metal dichalcogenides (TMDs),

their optical gain remains limited because of the poor light absorption in atomically

thin, layered materials. Most approaches to improve the optical gain of TMDs mainly

involve modulation of the active materials or multilayer stacking. Here, we report a

method to enhance the optical absorption and emission in MoS2 simply through the

design of a nanostructured substrate. The substrate consisted of a dielectric nanofilm

spacer (TiO2) and metal film. The overall photoluminescence intensity from monolayer

MoS2 on the nanostructured substrate was engineered based on the TiO2 thickness and

amplified by Fabry–Perot interference. In addition, the neutral exciton emission was

selectively amplified by plasmonic excitations from the local field originating from

the surface roughness of the metal film with spacer thicknesses of less than 10 nm.

We further demonstrate that the quality factor of the device can also be engineered

by selecting a spacer material with a different refractive index.
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