Transition metal dichalcogenides (TMDs) such as WS2 exhibit intriguing properties in monolayer form including direct bandgaps and large exciton binding energies. A major challenge in harnessing their potential is the uniform growth of high quality monolayers over large substrate areas. Metalorganic chemical vapor deposition (MOCVD) is a promising technique for TMD synthesis but the impact of precursor chemistry on TMD growth and properties is not well understood at present. In this work, the 2DCC-MIP team investigated the effect of the choice of chalcogen precursors in a cold-wall reactor geometry for the specific case of WS2.
The investigation reveals that  diethyl sulfide (DES) results in incorporation of carbon in the films, which can be correlated to a reduced lateral growth rate and quenching of photoluminescence from the WS2 films compared to growth with hydrogen sulfide (H2S). As a part of this investigation, thermodynamic modelling was also employed to understand the possible reaction outcomes. The calculations predict the formation of carbon when DES is used for growth consistent with the experimental observations. These results help in identifying promising precursors for the synthesis of high quality TMD films.