Solution-Based Synthesis of Few-Layer WS 2 Large Area Continuous Films for Electronic Applications

Unlike MoS 2 ultra-thin films, where solution-based single source precursor synthesis for electronic applications has been widely studied, growing uniform and large area few-layer WS 2 films using this approach has been more challenging. Here, we report a method for growth of few-layer WS 2 that results in continuous and uniform films over centimetre scale. The method is based on the thermolysis of spin coated ammonium tetrathiotungstate ((NH 4 ) 2 WS 4 ) films by two-step high temperature annealing without additional sulphurization. This facile and scalable growth method solves previously encountered film uniformity issues. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to confirm the few-layer nature of WS 2 films. Raman and X-Ray photoelectron spectroscopy (XPS) revealed that the synthesized few-layer WS 2 films are highly crystalline and stoichiometric. Finally, WS 2 films as-deposited on SiO 2 /Si substrates were used to fabricate a backgated Field Effect Transistor (FET) device for the first time using this precursor to demonstrate the electronic functionality of the material and further validate the method.