Dataset of "Fabrication of Janus MoSSe and Janus WSSe"

Janus 2D Transition Metal Dichalcogenide (TMD) is formed by two different chalcogen atoms on each side of the metal plane (represented as Janus XMY, where M = transition metal; X = chalcogen at the bottom; Y = chalcogen at the top). Due to this broken out-of-plane mirror symmetry and electronegativity difference between top and bottom layers, Janus TMDs exhibit internal perpendicular electric field, which leads to an occurrence of variety of novel physical phenomena. In this study, we have observed the hexagonal TMDs, namely MoSe2 and WSe2 during the sulfurization process, with the aim to fabricate Janus MoSSe and WSSe structures, respectively. The reaction was carried out inside the scanning electron microscope (SEM) chamber, equipped with a custom-build chemical vapour deposition (CVD) gas delivery system. This setup allows to use of H2S gas as a sulphur source for selective substitution of selenium atoms. In-situ SEM experiments have shown that it is possible to observe morphological changes induced by high temperature, as well as to track the chalcogen exchange process in both monolayer and multilayer materials. Raman spectroscopy confirmed the presence of Janus structure, showing that these stackings are more easily formed in multilayer systems than in monolayers. Additionally, for monolayers, photoluminescent spectra showed quenching where defects were present due to the absence of chalcogenide atoms, as well as emergence of a mixture of states (WS2(1-x)Se(2x)) that appeared at high temperatures, instead of a well-defined Janus monolayer.