Core-Shell WO3-WS2 Nanostructured Thin Films via Plasma Assisted Sublimation and Sulfurization

The present work describes the synthesis of WO3/WS2 core-shell nanorods (NRs) using plasma assisted sublimation followed by sulfurization process. In this process, WO3 nanostructured thin films were deposited using resistively heated tungsten (W) strip in the presence of O-2 plasma and their subsequent sulfurization at different temperatures in the presence of H2S/Ar plasma. The sulfurization temperature (T-s) was varied from 150 to 550 degrees C in order to obtain the core-shell WO3/WS2 with varying shell thickness. The structural properties of the as-obtained core-shell nanostructures were studied using XRD, Raman spectroscopy, XPS, and morphological properties using SEM, HR-TEM. It is observed that an intermediate oxidation state (5+) of W is formed during the conversion of WO3 (6+) into WS2 (4+). The use of plasma reduced the energy barrier required for sulfurization. The mechanism for sulfurization of WO3 NRs in the presence of reactive species of H2S/Ar plasma is also proposed.