Growth of bilayer transition metal dichalcogenides at controlled locations

Layered transition metal dichalcogenide (TMD) materials have attracted great interest for applications in electronics. Here, we report a method to synthesize TMD materials at controlled locations with the desired layer number. Metal oxide precursors are patterned on the growth substrate by photolithography, and then a mixture of sodium chloride and sodium cholate growth promoters is applied to enable the growth of monolayer and bilayer TMDs with large flake sizes. The quality of the bilayer flakes is examined by atomic force microscopy, Auger electron spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, and transmission electron microscopy. Electrical performance is evaluated by fabricating three-terminal field-effect transistors that demonstrate high carrier mobilities and on/off ratios larger than 105. This approach provides insights into future device applications and integration strategies based on layered TMD materials.