Controlled synthesis of high-quality crystals of monolayer MoS2 for nanoelectronic device application

Two-dimensional layered materials have attracted significant interest for their potential applications in electronic and optoelectronics devices. Among them, transition metal dichalcogenides (TMDs), especially molybdenum disulfide (MoS2), is extensively studied because of its unique properties. Monolayer MoS2 so far can be obtained by mechanical exfoliation or chemical vapor deposition (CVD). However, controllable synthesis of large area monolayer MoS2 with high quality needs to be improved and their growth mechanism requires more studies. Here we report a systematical study on controlled synthesis of high-quality monolayer MoS2 single crystals using low pressure CVD. Large-size monolayer MoS2 triangles with an edge length up to 405 mu m were successfully synthesized. The Raman and photoluminescence spectroscopy studies indicate high homogenous optical characteristic of the synthesized monolayer MoS2 triangles. The transmission electron microscopy results demonstrate that monolayer MoS2 triangles are single crystals. The back-gated field effect transistors (FETs) fabricated using the as-grown monolayer MoS2 show typical n-type semiconductor behaviors with carrier mobility up to 21.8 cm(2) V-1 s(-1), indicating excellent electronic property comparing with previously reported CVD grown MoS2 monolayer. The MoS2 FETs also show a high photoresponsivity of 7 A W-1, as well as a fast photo-response time of 20 ms. The improved synthesis method recommended here, which makes material preparation much easier, may strongly promote further research and potential applications.