Growth of large area few-layer or monolayer MoS2 from controllable MoO3 nanowire nuclei

Abstract

Here, we report a novel intermediate state (core–shell MoO₃–MoS₂ nanowires) in the synthesis of large area few-layer or monolayer MoS₂ films on Si/SiO₂ substrates coated with 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) using a chemical vapour deposition (CVD) method. In our experiments, water vapor present in the carrier gas (N₂) should help enhance the interaction between PTCDA and MoO₃. In the intermediate state, the morphology of the nuclei is controlled to be nanowires with 20–180 nm diameters and 30–70 μm lengths. We investigate the formation mechanism of the nucleation-controlled intermediate state and the formation process of monolayer MoS₂ using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), photoluminescence (PL), Raman spectroscopy and transmission electron microscopy (TEM) measurements. We also describe a method to control the diameter of the nanowires and the stacking of the nanowires into MoS₂ nanosheets on the substrate, which is meaningful for producing large area and highly crystalline MoS₂ monolayers.