Growth of Single-Crystalline Cadmium Iodide Nanoplates, CdI/MoS (WS, WSe) 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) nanoplates using a vapor transport and deposition approach. Optical microscopy and scanning electron microscopy studies show that the resulting CdI 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 in hexagonal phase, which is also confirmed by the characteristic Raman A mode at 110 cm. High-resolution transmission electron microscopy and selected area electron diffraction reveal that the resulting CdI nanoplates are single crystals. Taking a step further, we show the CdI nanoplates were readily grown on other 2DLMs (e.g., WS, WSe, MoS), forming diverse van der Waals heterostructures. Using prepatterned WS monolayer square arrays as the nucleation and growth templates, we also show that regular arrays of CdI/WS vertical heterostructures can be prepared. The synthesis of the CdI nanoplates, heterostructures, and heterostructure arrays offers a valuable material system for 2D materials science and technology.