The Synthesis of WS2 Atomic Layers under Varying Source-Substrate Distance

Although monolayer WS2 (Tungsten Disulfide) has attracted many interest, controllable synthesis of large-area WS2 triangles is still challenging. Here, we report salt-assisted CVD growth of WS2 atomic layers using a kind of sandwich structure in a semi-sealed installation and firstly investigate the effect of the width of the hollow (Dss) of the structure. We demonstrated WS2 triangles growth up to 300 μm coverage and showed the effect of hollow on the crystal size. By optimizing the width of the domain, large-area WS2 films were obtained. We utilized optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and photoluminescence (PL). Our study provides method to fabricate large area WS2 flakes and the experiment is critical to building scalable devices.