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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.

Dual-color photodetection can increase detection accuracy due to the specific information from different wavelengths. Traditional dual-color detectors are based on double optical modules or photovoltage devices, which suffer from huge system weight or low gain. In this Letter, a novel dual-color photodetector with Ge/Graphene/CdS sandwich profile is proposed. While visible and infrared light is mainly absorbed by the CdS and Ge layers, respectively, photoelectrical signals from two wavelengths both conducted by graphene are extracted on time-sequence with different sampling frequencies. Based on a tailored interface process and epitaxy InGaAs instead of bulk Ge layer, the difference in response speed more than 3 orders of magnitude (76 kHz/14 Hz) was realized. Due to the photogating effect, the high gain was obtained for both wavelengths, and a photoresponse enhancement originated from the overlapping of local photogating field is observed. The device provided a new solution for high-gain and CMOS-compatible dual-color photodetection.