Chemical Vapor Deposition Growth of Homogeneous Stacked Polycrystalline WSe₂ with Branched Patterns for Modulating Light–Matter Interactions

Two-dimensional materials provide a new avenue to study light-matter interactions and have important prospects in the field of optical applications. However, electro-optic modulation ways hinged on external factors, thus restricting its direct applications. Using material with unique local microstructures to directly modulate light-matter interactions is an alternative protocol but still a challenge owing to the lack of a suitable material system. Herein, we designed a transition-metal dichalcogenide material system of homogeneous stacked polycrystalline WSe2 with branched patterns by chemical vapor deposition. Systematic characterizations indicated that the WSe2 crystals shared the key features, which consist of a large number of microstructures separated by grain boundaries. The light-WSe2 interactions are thus modulated by these isolated microstructures, where optical responses of second-harmonic generation and Raman scattering were regulated by quasi-periodic and alternating intensity fluctuation described as "enhancement quenching- enhancement quenching". Our result reveals that constructing material systems with native polycrystalline and stacked patterns is an effective way of modulating light-matter interactions. This alternating modulation may provide a new way for the optical applications of grating a light modulator.