Effects of atomic layer deposition on the optical properties of two-dimensional transition metal dichalcogenide monolayers

Two-dimensional semiconducting transition metal dichalcogenides (TMDs) have attracted significant interest due to their unique optoelectronic properties. More often, these materials are enclosed inside a dielectric layer that can work as an insulator for field-effect transistors. The insulating layer is typically grown with atomic layer deposition (ALD). Here, we study the effects on bare and hBN-covered monolayer MoS2 and WSe2 flakes with ALD TiO2 films. Our results reveal a significant shift and decrease in intensity in photoluminescence and Raman signals of the monolayer TMDs. Further analysis suggests that these changes are caused by chemical doping, strain, and dielectric screening after the ALD. Our study not only sheds light on the impact of ALD on the properties of TMDs, but also indicates ALD can be an alternative method to engineer the doping, strain and dielectric environment for potential optoelectronics and photonics applications.

Automated summary

Two-dimensional semiconducting transition metal dichalcogenides (TMDs) have unique optoelectronic properties, and are often enclosed in a dielectric layer grown with atomic layer deposition (ALD). This study investigates the effects of ALD on the properties of monolayer TMDs, specifically MoS2 and WSe2, by analyzing the changes in photoluminescence and Raman signals. The results show a significant shift and decrease in intensity, which are attributed to chemical doping, strain, and dielectric screening after the ALD. This research highlights the potential of ALD as an alternative method for engineering the doping, strain, and dielectric environment in TMDs for optoelectronics and photonics applications.