Thin-film transition metal dichalcogenide growth fromheterostructuredbulk metallic patterns

Much research has been dedicated to synthesis of two-dimensional transition metal dichalcogenide (TMD) materials as well as their alloys and heterostructures, particularly by chemical vapor deposition (CVD). We will present initial investigations into potential alloying and heterostructure formation using a CVD method where vertical stacks of bulk transition metal films (Mo and W) are deposited in lithographically defined patterns which act as source material for the CVD reaction. Resultant lateral TMD growth was found to depend on the stacking order of the Mo and W. Interestingly, we have observed that often the predominant TMD formed is based on the first metal deposited, though covered by the second metal. For example, when W is the bottom metal, the lateral growth is predominantly WS₂ in all samples even though the W is ‘capped’ by the Mo. Whereas, when Mo is the bottom metal, the growth is predominantly MoS₂ in half of the samples and WS₂ in the other half, for given growth conditions. For specific growth parameters we observe an enhancement in the WS₂ growth in the presence of the Mo capping. We will present results from characterization using Raman and photoluminescence spectroscopy, SEM imaging, and EDX and discuss possible growth mechanisms.