14:45 〜 15:00
▲ [21p-H103-7] An effective approach to synthesize monolayer tungsten disulfide crystals using tungsten hexachloride
キーワード：WS2,CVD,solution casting
The transition metal dichalcogenides (TMDs) based layered materials (MoS2, WS2 etc.) have attracted significant interest as two dimensional (2D) semiconductor with a direct band gap. Recently, WS2 has gaining a lot of attention and it is constructed with a sandwich of two atomic layers of S and one atomic layer of W through covalent W–S bonds, respectively [1]. Here, we demonstrate a process to control the nuclei for growth of large WS2 crystals by solution-casting the WCl6 precursor on substrate. In the developed process, a 0.05M solution of WCl6 was drop-casted on the substrate, which was loaded in the center of small diameter tube sealed at one-end. A boat with 200 mg of S powder was placed in the center of low temperature furnace. Sulfurization experiments were performed at a temperature of 750 C in 80 sccm Ar atmosphere. Finally, the furnace was cooled down to room temperature and samples were removed from the tube.
We observed the growth of triangular (more than 50 μm), star-shaped WS2 crystals. Figure 1a shows a triangular monolayer WS2 crystal of 50 μm size. Figure 1b shows a six pointed star-shaped crystal. Figure 1c shows an AFM image of the as-synthesized WS2 crystal on SiO2/Si substrate. Line profile at the edge revealed an approximate thickness of around 0.9 nm, which is almost comparable to monolayer WS2 crystal.
We observed the growth of triangular (more than 50 μm), star-shaped WS2 crystals. Figure 1a shows a triangular monolayer WS2 crystal of 50 μm size. Figure 1b shows a six pointed star-shaped crystal. Figure 1c shows an AFM image of the as-synthesized WS2 crystal on SiO2/Si substrate. Line profile at the edge revealed an approximate thickness of around 0.9 nm, which is almost comparable to monolayer WS2 crystal.