Fabrication of Oxidized Transition Metal Dichalcogenides Monolayers for van der Waals Heterostructure

This study explores oxidized monolayer transition metal dichalcogenides (TMDs) as a new functional layer in van der Waals (vdW) heterostructures. We investigated the influence of mild O₂ plasma treatment on the optical properties of TMDs. Single-layer and multilayer samples of TMDs were prepared using metal-organic chemical vapor deposition (MOCVD) and mechanical exfoliation. Thickness was determined by optical contrast, photoluminescence (PL), and Raman spectroscopy. We systematically investigated the effect of O₂ plasma treatment on the optical properties of TMDs. Raman spectroscopy exhibited notable peak shifts in the E_2g and A_1g modes of TMDs with O₂ plasma treatment, indicating the formation of TMD oxides on the surface layer. PL spectroscopy showed changes in emission intensity and peak positions, further corroborating the selective oxidation of the surface layers. Interestingly, the oxidized monolayers of TMDs exhibited enhanced optical transparency, which is attributed to the reduced excitonic effect due to oxidation. This makes oxidized TMDs promising as a functional layer in vdW heterostructures based optoelectronic devices, where high transparency is essential. Furthermore, oxidized surface layers act as effective protective layers. These layers prevent the degradation of the underlying material, thereby enhancing the lifetime and reliability of the devices.<br/>We fabricated vdW heterostructures using oxidized monolayer TMDs as a constituent layer. The oxidized monolayers are easily integrated into the fabrication process of vdW heterostructures. A simple dry stamping method is used to create functional vdW heterostructures. Oxidized monolayers are used to control the interlayer interaction, which allows us to design the optical properties of the fabricated vdW heterostructures. Mild O₂ plasma treatment of TMDs offers a straightforward and effective method for enhancing their optical properties and functionality. The selective oxidation process enables the creation of heterostructures with tunable properties, improved stability, and enhanced performance. These findings highlight the potential of oxidized TMDs as transparent functional layers and protective coatings in van der Waals heterostructure-based optoelectronic devices.