Growth\nof Single-Crystalline Cadmium Iodide Nanoplates,\nCdI₂/MoS₂ (WS₂, WSe₂)\nvan der Waals Heterostructures, and Patterned Arrays

Abstract

Two-dimensional layered materials\n(2DLMs) have attracted considerable\nrecent interest for their layer-number-dependent physical and chemical\nproperties, as well as potential technological opportunities. Here\nwe report the synthesis of two-dimensional layered cadmium iodide\n(CdI₂) nanoplates using a vapor transport and deposition\napproach. Optical microscopy and scanning electron microscopy studies\nshow that the resulting CdI₂ nanoplates predominantly adopt\nhexagonal and triangular morphologies with a lateral dimension of\n∼2–10 μm. Atomic force microscopy studies show\nthat the resulting nanoplates exhibit a thickness in the range of\n5–220 nm with a relatively smooth surface. X-ray diffraction\nstudies reveal highly crystalline CdI₂ in hexagonal phase,\nwhich is also confirmed by the characteristic Raman A_g mode\nat 110 cm^–1. High-resolution transmission electron\nmicroscopy and selected area electron diffraction reveal that the\nresulting CdI₂ nanoplates are single crystals. Taking a\nstep further, we show the CdI₂ nanoplates were readily\ngrown on other 2DLMs (<i>e</i>.<i>g</i>., WS₂, WSe₂, MoS₂), forming diverse van der\nWaals heterostructures. Using prepatterned WS₂ monolayer\nsquare arrays as the nucleation and growth templates, we also show\nthat regular arrays of CdI₂/WS₂ vertical heterostructures\ncan be prepared. The synthesis of the CdI₂ nanoplates,\nheterostructures, and heterostructure arrays offers a valuable material\nsystem for 2D materials science and technology.