The morphologies of transition metal dichalcogenides (TMDCs) are most triangle shapes, while dendritic shape is really rare. Herein, we report a universal CVD method to fabricate the atomic thin 2H phase MoS2 dendrites on three single crystal substrate surfaces: rutile-TiO2 (001), SrTiO3 (001) and sapphire (0001), each having a different lattice geometry. Interestingly, by carefully tuning the concentration of Mo adatoms, we find that the MoS2 dendrites on these substrates exhibit the same morphological evolution from the tridental dendrites in low Mo concentration to the semi-compact fractal, and then to the compact triangular shape in high Mo concentration. Combing with experimental and theoretical analyses, we indicate the growth of MoS2 is not thermodynamics growth, instead, it is intrinsically a non-equilibrium process dominated by the kinetics of Mo adatoms. First-principles calculations indicate that the edge diffusion barrier of Mo is comparable to the attachment barrier of Mo, which means that fast atom diffusion along the edge is prevented. Kinetics Monte Carlo (kMC) simulations including different concentrations of Mo atoms represent the experimental grain evolutions well. Our results insightfully indicate Mo adatom concentration gradient is the key factor to control the morphology evolution of MoS2 from the dendritic to compact triangular grains, which are helpful for the understanding and structural controlling of morphology of TMDCs.

Dr. Ruifen Dou obtained her PhD from Institute of Physics, Chinese Academy of Sciences in 2004. Then she moved to Physikalisches Institut, Westf"alische Wilhelms-Universit"at of Muenster, Germany and worked as a post-doctor fellow for 2 years. After that, she joined the Department of Physics, Beijing Normal University as an Associate Professor. Now her research interests mainly focuses on controlling growth of the 2D layered materials (graphene/TMDs) by chemical vapor deposition (CVD) and study on their formation mechanism, electronic properties and modulation of the photo-electrocatalytic properties through the interface and morphology engineering tuning of these 2D layered materials. She has published more than 20 papers in Phys. Rev. Lett., 2D Materials, Phys. Rev. B, Nanoscale, J. Phys. Chem. C etc.