Facile synthesis of large-area and highly crystalline WS2 film on dielectric surfaces for SERS

Abstract A facile fabrication of high-quality and large-area tungsten disulfide (WS 2 ) layers is demonstrated using a thermal decomposition of tetrathiotungstates ((NH 4 ) 2 WS 4 ) with two annealing process. During synthesis, the first annealing step is utilized to achieve lateral epitaxial growth of the WS 2 and create seamless and large-area WS 2 film. The second annealing step can offer an S-rich and high temperature condition, which is beneficial for the high quality of the WS 2 film. Scanning electron microscopy, Raman spectroscopy and atomic force microscopy confirm the presence of large-area and high-quality WS 2 film. The crucial role of the S, H 2 and the effect of the temperature during the experiment are also investigated. Furthermore, the potential application of the prepared WS 2 as a substrate for Raman enhancement is first discussed using R6G molecules as probe molecule.