Laser-Assisted Chemical Modification of Monolayer Transition Metal Dichalcogenides

Laser-assisted chemical modification is demonstrated on ultrathin transition-metal dichalcogenides (TMDs), locally replacing selenium by sulfur atoms. The photoconversion process takes place in a controlled reactive gas environment and the heterogeneous reaction rates are monitored via in situ real-time Raman and photoluminescence spectroscopies. The spatially localized photoconversion results in a heterogeneous TMD structure, with chemically distinct domains, where the initial high crystalline quality of the film is not affected during the process. This has been further confirmed via transmission electron microscopy as well as Raman and photoluminescence spatial maps. This study demonstrates the potential of laser-assisted chemical conversion for on-demand synthesis of heterogeneous 2D materials with applications in nanodevices.