Influence of Carbon in Metalorganic Chemical Vapor Deposition of Few-Layer WSe Thin Films.

Metalorganic chemical vapor deposition (MOCVD) is a promising technique to form large-area, uniform films of monolayer or few-layer transition metal dichalcogenide (TMD) thin films; however, unintentional carbon incorporation is a concern. In this work, we report the presence of a defective graphene layer that forms simultaneously during MOCVD growth of tungsten diselenide (WSe) on sapphire at high growth temperature and high Se:W ratio when using tungsten hexacarbonyl (W(CO)) and dimethyl selenide ((CH)Se, DMSe) as precursors. The graphene layer alters the surface energy of the substrate reducing the lateral growth and coalescence of WSe domains. The use of hydrogen selenide (HSe) instead of DMSe eliminates the defective graphene layer enabling coalesced monolayer and few-layer WSe films. [ABSTRACT FROM AUTHOR]