CVD controlled preparation and growth mechanism of 2H-WS2 nanosheets

In this work, tungsten disulfide (WS2) nanosheets with good morphology are prepared by improved chemical vapor deposition (CVD) using a mixture of transition metal oxides and chalcogenide as precursors. By optimizing the growth conditions, the high-quality WS2 nanosheets with different morphologies, including large triangular, hexagonal, small triangular, terraced and spiral structures are obtained as the growth temperature of 850 °C, Ar gas flow rate of 50 sccm and holding time for 15 min. The detailed structural analyses by XRD, XPS, TEM and Raman measurements suggest that that the deposited WS2 nanosheets exhibit the 2H phase structure with high crystallization quality and uniform distribution of W and S elements. The formation of large triangular, hexagonal, and small triangular structures is related to the growth rate of different crystal planes of S atoms or W atoms. In addition, the formation of terraced and spiral stacking structures originates from the difference of supersaturation of precursors, which can be explained by the layer-by-layer stacking (LBL) growth and the spiral-dislocation-driven (SDD) mechanisms, respectively.