Competitive Growth Mechanism of WS2/MoS2 Vertical Heterostructures at High Temperature

The morphology of Van der Waals heterostructures is one of the most important factors that influence the device performance in practical applications. Herein, we used two-step chemical vapor deposition (CVD) method to grow WS2/MoS2 vertical heterostructures on SiO2/Si substrate at high temperature. Optical microscopy, Raman spectroscopy and scanning electron microscopy are used to characterize their morphology and structure properties. At high temperature, the edge atoms in the MoS2 matrix are ready to detach in two different manners. Through competition between desorption of MoS2 and adsorption of WS2, two unusual morphologies with dendritic and tassel edges are formed, which are otherwise not observed for purely thermal desorption of MoS2 at the same condition. The growth mechanisms are discussed in terms of both thermodynamics and kinetic factors.