Poisoning of MoO3 Precursor on Monolayer MoS2 Nanosheets Growth by Tellurium-Assisted Chemical Vapor Deposition

We obtain molybdenum disulfide (MoS2) nanosheets (NSs) with edge sizes of 18 mu m by direct sulfuration of MoO3 powder spread on the SiO2/Si substrates. However, the undesirable MoO3 nanoparticles (NPs) left on the surface of MoS2 NSs poison the MoO3 precursor. Introducing Te vapors to react with MoS2 to form low melting point intermediate MoSx Te2-x, the evaporations of MoO3 precursor recover and MoO3 NPs disappear. Thus Te vapor is effective to suppress poisoning of the MoO3 precursor. Selecting the appropriate amount of Te vapor, we fabricate monolayer MoS2 NSs up to 70 mu m in edge length. This finding can be significant to understand the role of Te in the Te-assisted chemical vapor deposition growth process of layered chalcogenide materials.