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, WS 2 dendrites with unique 6-fold symmetry produced on the surface of a two-dimensional monolayer WS 2 film were successfully obtained on a SiO 2 /Si substrate by the chemical vapor deposition method. A monolayer WS 2 film with pristine hexagonal symmetry plays a crucial role in stimulating the formation of a WS 2 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 WS 2 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.

Two-dimensional tungsten disulfide (WS 2 ), as one of the widely concerned members of the transition metal dichalcogenides family, has been studied broadly by its outstanding photonic and electronic properties. Since all of the research works focus on size and the number of layers, the dendritic structure WS 2 has been scarcely reported. In our study, we make use of atmospheric pressure chemical vapor deposition (APCVD) to control the synthesis of dendritic WS 2 /monolayer WS 2 heterostructures on the SiO 2 /Si substrate. The stacking morphology of the heterostructure is verified by AFM, Raman, and PL spectra. The effects of growth times and carrier gas flux on the quasiepitaxial growth of WS 2 films with dendritic structures have been systematically studied. In addition, the transition between fractal, dendritic, and compact morphologies with the increase of the growth times (carrier gas flux) are more significant. The compact morphology and difference of contact potential between the adjacent dendritic structures are characterized by Kelvin probe force microscopy (KPFM). Moreover, the as-fabricated FET devices exhibit excellent electronic properties (on/off ratio, carrier mobility, photoresponsivity, and response time are about 10 6 , 11.42 cm 2 V −1 S 1− , 46.6 mA/W, and 105.5 μs, respectively). This study paves the way for the rational design of high-sensitivity fractal-enhanced phototransistor devices for industrial and commercial applications.

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