Growth of Single-Crystalline Cadmium Iodide Nanoplates, CdI₂/MoS₂ (WS₂, WSe₂) van der Waals Heterostructures, and Patterned Arrays

Two-dimensional layered materials (2DLMs) have attracted considerable recent interest for their layer-number-dependent physical and chemical properties, as well as potential technological opportunities. Here we report the synthesis of two-dimensional layered cadmium iodide (CdI 2 ) nanoplates using a vapor transport and deposition approach. Optical microscopy and scanning electron microscopy studies show that the resulting CdI 2 nanoplates predominantly adopt hexagonal and triangular morphologies with a lateral dimension of ∼2–10 μm. Atomic force microscopy studies show that the resulting nanoplates exhibit a thickness in the range of 5–220 nm with a relatively smooth surface. X-ray diffraction studies reveal highly crystalline CdI 2 in hexagonal phase, which is also confirmed by the characteristic Raman A g mode at 110 cm –1 . High-resolution transmission electron microscopy and selected area electron diffraction reveal that the resulting CdI 2 nanoplates are single crystals. Taking a step further, we show the CdI 2 nanoplates were readily grown on other 2DLMs ( e . g ., WS 2, WSe 2, MoS 2 ), forming diverse van der Waals heterostructures. Using prepatterned WS 2 monolayer square arrays as the nucleation and growth templates, we also show that regular arrays of CdI 2 /WS 2 vertical heterostructures can be prepared. The synthesis of the CdI 2 nanoplates, heterostructures, and heterostructure arrays offers a valuable material system for 2D materials science and technology.