Isomeric Compound Dendrites on a Monolayer WS₂Substrate: Morphological Engineering and Formation Mechanism

Dendritic morphology as a defining feature for a large number of natural things like pinetrees, snowflakes, and neuronal cells is attractive and ubiquitous in nature. Until now, the formation mechanism of a dendritic structure based on some type of nonequilibrium growth process not only for those around nature but also for synthetic materials is still far from being clearly understood. Herein, WS2 dendrites with unique 6-fold symmetry produced on the surface of a two-dimensional monolayer WS2 film were successfully obtained on a SiO2/Si substrate by the chemical vapor deposition method. A monolayer WS2 film with pristine hexagonal symmetry plays a crucial role in stimulating the formation of a WS2 dendritic structure. In addition, these dendrites exhibit an average fractal dimension of ∼1.90, which is larger than the classical fractal dimension of ∼1.66 deduced by diffusion-limited aggregation. The first-principles calculations indicate that the prominent diffusion anisotropy of a monomer precursor and the lattice symmetry of a WS2 film determine the evolution of a dendritic structure. This work will reveal in detail and represent the intrinsic mechanism and dynamic process in the nonequilibrium crystal growth of two-dimensional crystals. Furthermore, it will be potential to instruct the artificial design and synthesis of an isomeric dendritic structure by morphology engineering on the basis of two-dimensional crystals.