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.