Growth of submillimeter-scale single crystal 2D BiI3 by the cooling-induced growth method in a confined space

Due to its nontoxicity, suitable bandgap, high defect tolerance and high electron mobility, layered BiI 3 has been gaining attention in photoelectric device and nonlinear optics field. However, the growth of large-size single crystal 2D BiI 3 has not been achieved. Herein, the synthesis of single crystal 2D BiI 3 on mica substrate via a cooling-induced growth method is reported, with the thickness of 8 ∼ 1000 nm and a lateral dimension of 110 ∼ 1000 μm. X-ray diffraction and selected area electron diffraction demonstrate the single crystal nature of 2D BiI 3 flakes. The high temperature during heat preservation step prevents the deposition of BiI 3 vapor, and then, when proceeding to cooling-induced growth step, single crystal 2D BiI 3 flakes start to nucleate on colder mica substrate and grow up to ∼ 1000 μm (lateral dimension) rapidly. The stability test indicates the 2D BiI 3 flake decomposes with the present of both O 2 and water. Finally, the cooling rate, height of crucible, holding temperature and type of substrate have also been investigated to show the structural evolution of 2D BiI 3 flakes.