Growth of large edge length two-dimensional WS2 using a custom 12-zone atmospheric pressure chemical vapor deposition system

Abstract

Transition metal dichalcogenides like WS2 exhibit technologically relevant optoelectronic properties. In this work, we report on the growth of two-dimensional tungsten disulfide of various geometries and morphologies using a custom atmospheric pressure chemical vapor deposition system. In triangular flakes, a maximum edge length of ∼110 μm (for multilayer) and ∼60 μm (for monolayer) was observed optically. Energy dispersive x-ray analysis yielded a W:S ratio close to a 1:2 stoichiometry. Two sets of intensity ratios (2LA(M)A1g), derived from Raman measurements, were found: ∼2.15 and ∼0.56, corresponding, respectively, to monolayer and multilayer growth of WS2. Photoluminescence measurements yield peaks at ∼640 and ∼660 nm, with the former peak (assigned to monolayer growth) exhibiting a ∼20-fold enhancement with respect to the latter (multilayer growth), suggesting a radiatively more efficient direct bandgap. It is expected that the process will lead to advancements in the growth of large-area two-dimensional transition metal dichalcogenides for device applications.