Chemical vapor deposition of clean and pure MoS₂crystals by the inhibition of MoO_3-xintermediates

Molybdenum disulfide (MoS2) synthesized via chemical vapor deposition (CVD) is commonly accompanied by some intermediate products in the form of MoO3-x, resulting in MoS2-MoO3-x hybrids with diverse structures. In this study, we show that through the rational design of heating evaporation rate of the precursors of sulfur and MoO3 separately in a CVD system with double temperature zones, the intermediate product of MoO3-x involved in the CVD growth of MOS2 (generally in the form of quadrilateral MoO2/MoS2 composites and/or stacks of quadrilateral MoO2/triangular MoS2) can be inhibited largely. On this basis, the appropriate sulfur sublimation versus the evaporated MoO3 powder is revealed to be the key factor for the inhibition of intermediates, obtaining high-quality MoS2 crystals with as high as >90% cleanness/purity. This study will assist our understanding of the fundamental CVD growth mechanisms of transition metal dichalcogenides (TMDCs) and provides a facile direction for the controlled synthesis of high-quality MoS2 and other TMDCs with or without intermediate hybrids for applications.