Preserving the Emission Lifetime and Efficiency of a Monolayer Semiconductor upon Transfer

Monolayer transition metal dichalcogenides (TMDs) are promising semiconductors for nanoscale photonics and optoelectronics due to their strong interactions with light. However, processes that integrate TMDs into nanophotonic and optoelectronic devices can introduce defects in the monolayers, resulting in lower emission efficiency. Quality control is therefore needed to process monolayer semiconductors effectively. Through micro-photoluminescence and fluorescence lifetime imaging measurements, this work investigates the effects of encapsulation on the optical properties of TMD monolayers, focusing on the impact of different processing techniques and different dielectric environments. Spin coating a polymer layer on top of a TMD monolayer is shown to significantly reduce its emission lifetime and efficiency. In contrast, the soft transfer of a monolayer deposited on a polymer superstrate can preserve its intrinsic emission properties almost perfectly in various dielectric environments. This approach can be widely applied to integrate TMDs into devices and heterostructures while protecting sample quality, and demonstrates that intrinsic quantum efficiency and photoluminescence lifetimes of TMDs can be preserved upon transfer to different dielectric substrates.